Biomedical subjects
Publications and source records attributed to J Gold.
On 19 April 2001, the Supreme Court of Canada released its first judgments in litigation alleging the Canadian Red Cross Society was negligent for inadequately screening blood donors in the early 1980s. It upheld an order that damages in the amount of over $2.5 million be paid to three individuals who contracted HIV between 1983 and 1985 from contaminated blood.
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Bacteria adhere to almost any surface, despite continuing arguments about the importance of physico-chemical properties of substratum surfaces, such as hydrophobicity and charge in biofilm formation. Nevertheless, in vivo biofilm formation on teeth and also on voice prostheses in laryngectomized patients is less on hydrophobic than on hydrophilic surfaces. With the aid of micro-patterned surfaces consisting of 10-microm wide hydrophobic lines separated by 20-microm wide hydrophilic spacings, we demonstrate here, for the first time in one and the same experiment, that bacteria do not have a strong preference for adhesion to hydrophobic or hydrophilic surfaces. Upon challenging the adhering bacteria, after deposition in a parallel plate flow chamber, with a high detachment force, however, bacteria were easily wiped-off hydrophobic lines, most notably when these lines were oriented parallel to the direction of flow. Adhering bacteria detached slightly less from the hydrophilic spacings in between, but preferentially accumulated adhering on the hydrophilic regions close to the interface between the hydrophilic spacings and hydrophobic lines. It is concluded that substratum hydrophobicity is a major determinant of bacterial retention while it hardly influences bacterial adhesion.
The use of phosphodiesterase inhibitors such as milrinone in the treatment of severe heart failure is frequently restricted because they cause vasodilation and hypotension. In patients with decompensated heart failure with hypotension after treatment with milrinone, low doses of vasopressin restored blood pressure without inhibiting the inotropic effect of milrinone.
OBJECTIVES: To identify risk factors for non-Hodgkin's lymphoma (NHL) in people with HIV infection. DESIGN AND SETTING: Case-control study in Sydney, Australia. PARTICIPANTS AND METHODS: Two hundred and nineteen patients with AIDS-related NHL were compared with 219 HIV-infected controls without NHL, matched for CD4 positive cell count and date of specimen collection. Data on demographic, infectious, treatment-related and immunological factors were abstracted by medical record review. The association between demographic factors, sexually transmissible diseases, HIV-related opportunistic infections, anti-viral therapy, duration of immune deficiency and indices of immune stimulation and risk of NHL were derived for these groups. RESULTS: In a multivariate model, there were two independent groups of predictors of NHL risk. The first was duration of immunodeficiency, as measured by longer time since seroconversion (P for trend 0.008), and lower CD4 positive cell count 1 year prior to the time of NHL diagnosis (P for trend 0.009). The second predictor was B-cell stimulation, as indicated by higher serum globulin (a surrogate marker for serum immunoglobulin, P for trend 0.044) and HIV p24 antigenaemia [odds ratio (OR) for p24 positivity, 1.82; 95% confidence interval (CI), 1.15-2.88]. Indices of B-cell stimulation preceded the diagnosis of NHL by several years. Factors not related to NHL risk included clinical indices of Epstein-Barr virus infection and receipt of individual nucleoside analogue antiretroviral agents. Combination therapy with these agents was associated with a non-significant reduction in NHL risk (OR, 0.68; 95% CI, 0.39-1.18). CONCLUSIONS: Markers of long-standing immune deficiency and B-cell stimulation were associated with an increased risk of developing NHL. Unless the strongest risk factor for NHL, immune deficiency, can be reversed, NHL is likely to become proportionately more important as a cause of morbidity and mortality in people with HIV infection.
In this study room temperature vulcanized (RTV) silicone surfaces with designed surface microstructure and well-defined surface chemistry were prepared. Their resistance to marine macrofouling by barnacles Balanus improvisus was tested in field experiments for deducing optimal surface topography dimensions together with a better understanding of macrofouling mechanisms. Polydimethylsiloxane (PDMS) surfaces were microstructured by casting the PDMS pre-polymer on microfabricated molds. The master molds were made by utilizing photolithography and anisotropic etching of monocrystalline silicon wafers. Several iterative casting steps of PDMS and epoxy were used to produce large quantities of microstructured PDMS samples for field studies. The microstructured PDMS surface consisted of arrays of pyramids or riblets creating a surface arithmetic mean roughness ranging from 5 to 17 microm for different microstructure sizes and geometries, as determined by scanning electron microscopy. Chemophysical properties of the microstructured films were investigated by electron spectroscopy for chemical analysis, time-of-flight secondary ion mass spectroscopy and dynamic contact angle measurements. Films were chemically homogeneous down to the submicron level. Hydrophobicity and contact angle hysteresis increased with increased surface roughness. Field tests on the west coast of Sweden revealed that the microstructure containing the largest riblets (profile height 69 microm) reduced the settling of barnacles by 67%, whereas the smallest pyramids had no significant influence on settling compared to smooth PDMS surfaces. The effect of dimensions and geometry of the surface microstructures on the B. improvisus larvae settling is discussed.
Perceptual discrimination improves with practice. This 'perceptual learning' is often specific to the stimuli presented during training, indicating that practice may alter the response characteristics of cortical sensory neurons. Although much is known about how learning modifies cortical circuits, it remains unclear how these changes relate to behaviour. Different theories assume that practice improves discrimination by enhancing the signal, diminishing internal noise or both. Here, to distinguish among these alternatives, we fashioned sets of faces and textures whose signal strength could be varied, and we trained observers to identify these patterns embedded in noise. Performance increased by up to 400% across several sessions over several days. Comparisons of human performance to that of an ideal discriminator showed that learning increased the efficiency with which observers encoded task-relevant information. Observer response consistency, measured by a double-pass technique in which identical stimuli are shown twice in each experimental session, did not change during training, showing that learning had no effect on internal noise. These results indicate that perceptual learning may enhance signal strength, and provide important constraints for theories of learning.
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To better understand how the visual system makes use of information across spatial scales when identifying different kinds of complex patterns, we measured human and ideal contrast identification thresholds to estimate identification efficiency for 1- and 2-octave wide band-pass filtered letters and faces embedded in 2-D dynamic Gaussian noise. Varying stimulus center frequency from 1 to 70 c/object had different effects on letter and face identification efficiency. In the 2-octave conditions, identification efficiencies decreased by 0.25-0.5 log units for letters and 0.5-1.2 log units for faces as center frequency increased from 6.2 to 49.5 c/object, but only letters were identifiable at center frequencies below 6.2 c/object. In the 1-octave conditions, letter identification efficiencies increased by about 0.5 log units as center frequency increased from 1.1 to 2.2 c/object, and were nearly constant from 2.2 to 35 c/object. Letters were unidentifiable by human observers at 70 c/object. Surprisingly, face identification was impossible for human observers at all center frequencies except 8.8 c/object for one observer, and 8.8 and 17.5 c/object for a second observer. Ideal observer thresholds were obtained for both letters and faces in all conditions, so information was always available to perform the task. Thus, the failure to identify faces reflects constraints on visual processing rather than a lack of stimulus information. Selective spatial sampling may account for some of the differences between letter and face identification efficiencies.
OBJECTIVE: Echocardiography is an important tool in the diagnosis and management of critically ill neonates. The authors hypothesized that live telemedicine guidance and interpretation of neonatal echocardiograms from underserved areas would improve management, prevent unnecessary transports, enhance sonographer proficiency, and result in monetary savings. MATERIALS AND METHODS: Using personal computers capable of real-time transmission of echocardiograms over three integrated services digital network (ISDN) telephone lines, pediatric cardiologists interpreted echocardiograms, suggested views to sonographers, and made recommendations to neonatologists 200 miles away. Analyses of accuracy, management, echocardiogram quality, time, and costs were carried out prospectively. RESULTS: Sixty studies were transmitted over 7 months. Indications for echocardiography were suspected congenital heart disease (n = 29), suspected patent ductus arteriosus (PDA) (n = 27), and hemodynamic instability (n = 4). Diagnoses were critical congenital heart disease (n = 4), noncritical heart disease (n = 8), PDA (n = 21), ventricular dysfunction (n = 5), persistent pulmonary hypertension (n = 3), and normal (n = 19). Videotape review confirmed all telemedicine interpretations. The echocardiogram led to immediate change in management in 25 cases (42%), and echocardiogram quality was improved in 53 studies (88%). Time from request to completion of echocardiography was 43+/-30 min. Monetary savings from five avoided transports exceeded all expenses. CONCLUSION: Live transmission of neonatal echocardiograms over three ISDN lines is diagnostic, improves patient care and echocardiography quality, and is cost effective.
UNLABELLED: In this randomized, double-blinded study, we compared the onset and recovery characteristics of an investigational benzodiazepine, Ro 48-6791 (when administered alone or combined with meperidine), a midazolam-meperidine combination for sedation during gastrointestinal (GI) endoscopic procedures. Ninety consenting outpatients scheduled for upper or lower GI procedures were randomly assigned as follows: Group I received midazolam 1 mg IV and meperidine 50 mg; Group II received Ro 48-6791 0.5 mg IV and meperidine 50 mg; or Group III received Ro 48-6791 1.0 mg IV alone. If the level of sedation did not achieve an Observer's Assessment of Alertness/Sedation (OAA/S) score of 4 (where 5 = awake/alert to 1 = asleep) in < or = 2 min, a second bolus dose, equal to half of the original dose of midazolam or Ro 48-6791, was administered. The onset time was defined as the time to achieve an OAA/S score of 4. During the procedure, a bolus dose equal to half of the total induction dose was given to maintain an OAA/S score of 4. The induction and maintenance dosages, as well as recovery times to an OAA/S score of 5, were recorded. A heel-toe line walk (HTLW) test used to determine the time to "fitness for discharge." Although the onset times were similar in all three groups, the induction dosages were significantly reduced in Group II compared with Groups I and III. There were significantly more patients requiring supplemental sedative boluses and "rescue" analgesia with Ro 48-6791 than with midazolam. The Ro 48-6791 groups also experienced more dizziness after the procedures. Ro 48-6791 was associated with a higher incidence of inadequate sedation (18% vs 3%) without the opioid. The time for the HTLW test to return to baseline values after the procedure was similar among the three groups. However, the Ro 48-6791 groups had significantly reduced times to return to an OAA/S score of 5 and to achieve the baseline HTLW value after the last dose of the benzodiazepine. In conclusion, compared with midazolam, Ro 48-6791 is more potent and may be associated with a more rapid early recovery after endoscopic GI procedures. However, sedation with Ro 48-6791 required more supplemental bolus doses and "rescue" analgesic medication and was associated with a higher incidence of dizziness. IMPLICATIONS: The investigational water-soluble benzodiazepine, Ro 48-6791, is a more potent sedative than midazolam, which appears to have a slightly shorter duration of action. Unfortunately, use of Ro 48-6791 increased the requirement for supplemental doses of the sedative medication and the need for "rescue" analgesics during the procedure and was associated with more dizziness after the procedure.
The effectiveness of a local collaborative quality improvement project in improving the management of postoperative pain for Wisconsin Medicare patients was assessed. Six quality indicators were evaluated on the basis of baseline data from 714 subjects at 15 collaborating hospitals and follow-up data from 406 subjects from the same 15 hospitals. After efforts to improve postoperative pain management, there was statistically significant improvement in all six quality indicators.
The past decades and current R&D of biomaterials and medical implants show some general trends. One major trend is an increased degree of functionalization of the material surface, better to meet the demands of the biological host system. While the biomaterials of the past and those in current use are essentially bulk materials (metals, ceramics, polymers) or special compounds (bioglasses), possibly with some additional coating (e.g., hydroxyapatite), the current R&D on surface modifications points toward much more complex and multifunctional surfaces for the future. Such surface modifications can be divided into three classes, one aiming toward an optimized three-dimensional physical microarchitecture of the surface (pore size distributions, "roughness", etc.), the second one focusing on the (bio) chemical properties of surface coatings and impregnations (ion release, multi-layer coatings, coatings with biomolecules, controlled drug release, etc.), and the third one dealing with the viscoelastic properties (or more generally the micromechanical properties) of material surfaces. These properties are expected to affect the interfacial processes cooperatively, i.e., there are likely synergistic effects between and among them: The surface is "recognized" by the biological system through the combined chemical and topographic pattern of the surface, and the viscoelastic properties. In this presentation, the development indicated above is discussed briefly, and current R&D in this area is illustrated with a number of examples from our own research. The latter include micro- and nanofabrication of surface patterns and topographies by the use of laser machining, photolithographic techniques, and electron beam and colloidal lithographies to produce controlled structures on implant surfaces in the size range 10 nm to 100 microns. Examples of biochemical modifications include mono- or lipid membranes and protein coatings on different surfaces. A new method to evaluate, e.g., biomaterial-protein and biomaterial-cell interactions--the Quartz Crystal Microbalance--is described briefly.
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