Biomedical subjects
R Nelson
Publications and source records attributed to R Nelson.
Sex ratio and heterozygote advantage in cystic fibrosis families.
The families of aunts and uncles of cystic fibrosis (CF) patients were compared with one another and with controls in order to test claims of increased fertility and sex ratio in families containing the CF allele and to identify the more fertile sex. Uncles' families were found to contain a significant excess of sons, particularly at primiparous births, as well as a significantly increased sex ratio. Reanalysis of published records of CF sibships confirmed the effect of parity on sex ratio. The families of uncles were also exceptional in exceeding the size intended, although their mean size was not raised significantly. It is suggested that these effects could be related to an interaction between CF-related, paternally-derived antigens and the maternal immune system.
Loperamide toxicity in severe protracted diarrhoea.
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Effect of healing on small internal diameter arterial graft compliance.
Porosity is an essential component for long term function of small internal diameter synthetic vascular prostheses. Theoretically, porosity is required for healing by providing a scaffold for ingrowth of periprosthetic tissues. Porosity may be required for transfer of fluids and ions in prostheses even if tissue ingrowth does not occur. Increased permeability of vascular grafts has been shown to enhance tissue incorporation. Implants with pore sizes greater than 10 microns but less than 45 microns become ingrown with fibrohistiocytic tissue and capillaries. Implants with pore sizes greater than 45 microns are ingrown with organized fibrous tissue and minimal histiocytic response. The phenomenon of differential ingrowth may have important functional significance. Prostheses which heal with organized fibrous tissue have the potential for long term contracture, strangulation of vascularity and calcification. Fibrohistiocytic tissue has low mechanical strength and does not appear to contract or calcify. Elastomeric microporous vascular prostheses which are minimally ingrown or ingrown with fibrohistiocytic tissue maintain compliance after months of implantation. This study was designated to determine the effects of healing on the compliance of small internal diameter vascular replacements and to correlate the compliance to patency rates.
Data processing as a tool in human resource management.
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[Biplexiform ganglion cells of the primate retina with direct contact with photoreceptors].
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Measurement of tracheal mucous transport rate in the horse.
Tracheal mucous transport rates were measured in 12 nonanesthetized horses after an intratracheal injection of 99mtechnetium-sulfur colloid. The transport rate of the subsequent bolus of radioactivity was determined, using a portable scaler rate meter fitted with a high-energy gamma-scintillation probe. A gamma-scintillation camera was used to verify bolus form and movement in 1 horse. The mean tracheal mucous transport rate was 1.66 +/- 0.24 cm/min.
Intestinal permeability in children with Crohn's disease and coeliac disease.
Mannitol and lactulose were used as probe molecules to measure intestinal permeability in children with active small-bowel Crohn's disease and with untreated coeliac disease. Mannitol and lactulose were administered by mouth in a moderately hypertonic solution (580 mmol (mosmol)/l), and results were expressed as the ratio of the molecules excreted in urine over five hours. Patients with Crohn's disease had a sixfold increase in permeability (due to increased lactulose permeability) and those with coeliac disease a fivefold increase (due to decreased mannitol permeability). From these results the test offers potential as a noninvasive investigation in children with small-bowel disease.
Noninvasive evaluation of peripheral vascular disease using transcutaneous oxygen tension.
Transcutaneous oxygen tension (PtcO2) was used for noninvasive determination of blood supply in 25 patients evaluated for peripheral arterial disease. PtcO2 values were compared with segmental Doppler pressure, pulse volume recording, pulse reappearance time, and angiography in patients being evaluated for wound healing problems, amputations, and peripheral bypass procedures. PtcO2 was measured using a heated (45 degrees C) Clark polarographic electrode to quantitate the oxygen which diffuses from the dermal capillaries to the skin surface. Control PtcO2 values recorded over the chest or shoulder taken while patients were breathing room air were 78 +/- 8 mm Hg. PtcO2 values greater than 50 mm Hg predicted success for levels of amputation and for wound healing without reconstructive procedures; values of 40 mm Hg or less were associated with continued wound problems and complication after amputation. Increased PtcO2 values after vascular reconstruction of the legs predicted improved clinical status on follow-up examinations up to 6 months. PtcO2 predicted the extent of vascular disease as well as the other noninvasive tests and angiography. We conclude that (1) PtcO2 tension is a simple, accurate, noninvasive method to determine the appropriate level of amputation, wound healing potential, and effectiveness of bypass procedures, and (2) PtcO2 values correlate well with angiography and noninvasive evaluations.
Virus-specific IgG and IgM antibodies in normal and immunocompromised subjects infected with cytomegalovirus.
Levels of IgG and IgM antibodies t human cytomegalovirus (CMV) were measured using a solid-phase radioimmunoassay. Individuals positive by complement-fixation test consistently had detectable IgG titers by radioimmunoassay, but no quantitative relationship was apparent. An elevated IgM titer was considered specific for CMV infection because sera from individuals with other herpesvirus infections did not cross-react. In patients with mononucleosis, elevated titers of IgM antibody to CMV correlated (P less than 0.001) with active infection and were highest during viremia. Titers of IgG antibody to CMV during and after symptomatic infection were similar to those of asymptomatic positive individuals. Increases in CMV-specific IGM were observed in both primary and reactivated infections in cardiac transplant recipients. In a small group of cardiac transplant recipients with recurrent symptomatic disease, IgM titers were low at the time of viruria and did not increase with CMV tissue involvement, a result which suggests that quantitative deficiencies in IgM may be related to the severity of CMV infections.
Failure of Padac test strips to detect staphylococcal beta-lactamase.
Padac test strips failed to detect the production of beta-lactamase by 10 strains of penicillin-resistant staphylococci.
AII amacrine cells quicken time course of rod signals in the cat retina.
1. In a perfused eyecup preparation, AII amacrine cells of the cat retina were penetrated with glass microelectrodes and their electrical responses to photic stimuli recorded. 2. Intracellular injections of the stains Procion, lucifer, or horseradish peroxidase revealed dendritic tree diameters of 30-80 micrometers (48 +/- 16 micrometers, mean +/0 SD) and cell body diameters from 7 to 12 micrometers (9 +/- 3 micrometers) for these cells. The dendrites were broadly stratified throughout the inner plexiform layer (IPL) but possessed large, terminal varicosities in the IPL and inner nuclear lyer (INL) proximal to the cell body. 3. The waveform of these cells in response to photic stimulation suggested division into four components: a) an initial rapid depolarization of the cell membrane followed by a slower decay toward the dark level; b) suppression of the dark noise of the cell; c) with dim or moderately intense stimuli, an off-hyperpolarization; d) in some cases a hyperpolarizing surround response. 4. The receptive fields of AII cells have been characterized using spatial stimuli consisting of long narrow slits. Curves have been fitted to spatial data using two space constants, one for the center mechanism and an opposing one for the surround. For the central mechanism, space constants ranged from 20 to 80 micrometers (46 +/- 22 micrometers), while for the surround they ranged from 60 to 130 micrometers (85 +/- 28 micrometers). The mean half-width of the center mechanism, calculated from the mean space constant, was about 0.25 degrees of visual angle (64 micrometers). The receptive-field properties of AII amacrine cells resemble those of center-depolarizing bipolar cells of other species. 5. Spectral studies of AII amacrine cells reveal that they are rod driven at all criterion voltage levels. Furthermore, adaptation of the rods by rod-saturating backgrounds eliminates 95% of the response amplitude of the AII amacrine cells. Under these conditions the tiny response component remaining is driven by the cat's long wavelength (556-nm peak) cones. 6. AII amacrine cells depolarize to rod stimulation more rapidly than other rod-dominated cells, such as rod bipolar cells, which hyperpolarize. For stimuli corresponding to about 10% of rod saturation, the latency to half-maximum amplitude is about 65 ms for AII cells, 40 ms faster than rod-dominated hyperpolarizing units. The leading edge of the response waveform for AII cells is also much more restricted in time. With the above stimulus it requires about 20 ms to increase from 25 to 75% of its peak, a period almost 4 times shorter than required by rod-dominated S-potential responses. With saturating stimuli the AII response requires only 5 ms to increase from 25 ot 75% of its peak. 7. Although prominent in the rod system, AII amacrine cells do not appear to be able to detect single quantum events. Threshold signals require the bleaching of about 200 rhodopsin molecules within a receptive field containing some 1,300 rods...
The effects of plasma and salivary constituents on dentin permeability.
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Spontaneous dissecting aneurysm of the extracranial vertebral artery.
Spontaneous dissection of a cervical vertebral artery secondary to fibromuscular hyperplasia is uncommon, is often painful, and may be followed after a latent interval by further symptoms of embolism, occlusion, or hemorrhage. Accordingly, the lesion is potentially hazardous and warrants treatment when recognized.
Perinatal asphyxia and multiple organ defects.
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Implant microstructure and collagen synthesis.
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The use of bacteria as markers of leukemic lymphocytes and for the isolation of natural killer cells.
Human lymphocyte subpopulations as well as leukemic lymphocytes can be identified and enumerated in blood smears by using bacteria that bind spontaneously to lymphocytes or by using bacteria to which antibodies are chemically coupled. The mechanism of natural binding of bacteria to lymphocytes was shown to involve a lectin on the lymphocyte surface and a carbohydrate on the bacteria. Also, we found that natural killer (NK) cells can be separated by negative selection using monolayers of bacteria. A subpopulation of T cells, identified by their binding of B. globigii, was shown to be suppressors for NK cells.
Use of dentine-fluid protein concentrations to measure pulp capillary reflection coefficients in dogs.
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