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Biomedical subjects

R Robb

Publications and source records attributed to R Robb.

At least 19 recordsLinked to original sources
PubMed1999

Neutrophil count and amputation in critical limb ischaemia.

BACKGROUND: The white blood cell count (WCC) is known to be predictive of cardiac and cerebral vascular events. No one has yet investigated this in critical limb ischaemia (CLI). METHODS: Baseline WCC was examined in relation to lower limb amputation 6 months after a 4 week treatment period with i.v. placebo or i.v. taprostene in 366 patients with CLI. RESULTS: The WCC was related to a significant increase in amputation, relative risk 1.6 (p=0.001, 95% CI: 1.2-2.0) in CLI patients with WCC > or =9x10(9)/l vs patients with WCC <9x10(9)/l. Its association with disabling amputation persisted on logistic regression analyses which included cigarette smoking as a variable and also treatment group (p<0.001). The WCC is therefore an easily measurable prognostic variable in CLI. CONCLUSIONS: The white blood cell may promote intractable tissue ischaemia by capillary plugging and/or release of toxic chemicals and may have distinct effects on tissue viability.

Amputation, Surgical↗
PubMed1999

Seasonal variation of Raynaud's phenomenon secondary to systemic sclerosis.

OBJECTIVE: Patients with systemic sclerosis (SSc) were assessed for 12 months to quantify the seasonal variation in Raynaud's phenomenon (RP) in patients with an underlying connective tissue disease. METHODS: Eighteen patients with SSc (17 limited, 1 diffuse type) were studied. Raynaud's attacks were recorded in a daily diary for four 2-week periods at 3 month intervals. Daily number and duration of attacks and overall severity of RP were calculated for each 2-week period. Mean daily temperatures, measured and perceived, were obtained for each period. RESULTS: In winter, patients had a mean of 2.9 attacks/day (SD +/-1.1), daily duration 70 minutes (SD +/-48) and a severity of score of 4.1 (SD +/-2.0) out of 10. All 3 variables correlated with ambient outdoor temperature and varied significantly over the 12 months (p<0.001) with mean reductions of 48, 50, and 56% respectively from winter to summer. Only 3 of 18 patients reported no attacks during the summer period. The mean measured and perceived outdoor temperatures increased from winter to summer by 10.6 and 14.3 degrees C, respectively. CONCLUSION: For patients with SSc, RP is a problem throughout the year. Symptoms may be reduced by about 50% in the summer months, but few patients experience complete relief.

Female↗
PubMed1997

The white blood cell adhesion molecule E-selectin predicts restenosis in patients with intermittent claudication undergoing percutaneous transluminal angioplasty.

BACKGROUND: Experimental studies have shown that endothelial dysfunction is an early event preceding restenosis. Monocytes and neutrophils have been shown to bind to damaged endothelium via the cell adhesion molecules (CAMs). The selectins are involved in capturing the leukocytes and tethering them to the endothelium. E-selectin is a CAM that is only expressed on activated endothelial cells. Its ligands are expressed on monocytes and neutrophils and it has been found to exist in a soluble form. This soluble form may represent a marker for endothelial damage and may be a precursor of smooth muscle proliferation. METHODS AND RESULTS: Fifty-four patients who were undergoing peripheral arterial balloon angioplasty had blood sampled before angioplasty. E-selectin was measured in plasma with the use of an ELISA. At follow-up angiogram, 30% (n=14) of the patients had restenosed at 1 year. There was a significant difference in baseline E-selectin levels in patients who restenosed compared with those who did not (65.3 ng/mL [58.25 to 78.05] versus 52.3 [34.2 to 62.1], Mann-Whitney U, P<.007). Endothelial activation with subsequent adherence of white blood cells is an important step in restenosis. CONCLUSIONS: We have shown an increased level of shed E-selectin in patients destined for restenosis and suggest that this work further supports a role for white blood cell/endothelial interaction in restenosis after angioplasty.

Adult↗
PubMed1994

Aided listener preferences in laboratory versus real-world environments.

A wearable, fully digital, personal processing unit developed for the study of hearing aid fitting and digital signal-processing techniques was utilized in a preliminary study of hearing aid fitting validation. In a modified single-subject, multiple-baseline control design, 12 hearing-impaired listeners indicated their preferences for monaurally aided frequency response alternatives during an initial laboratory session, a real-world session, and a final laboratory session. Listeners' preferences, based on listening to connected speech, were stored in each environment by the personal processing unit. Within blocks of 3 each, subjects were time-lagged with respect to the number of trials to criterion. Subjects participated in 1 of 4 listening conditions, classified according to laboratory stimulus materials; speech recorded in an audiometric sound room in quiet or noise, and speech recorded in a reverberant room in quiet or noise. When compared with preferences obtained in the initial laboratory session, preferences obtained during the final laboratory session agreed better with those obtained in the real world. Overall, however, preferences under laboratory conditions were only fair predictors of preferences under everyday conditions. Results reveal the potential of harnessing the programming and storage capabilities of digital signal-processing technology in implementing new hearing aid fitting strategies.

Acoustic Stimulation↗
PubMed1992

HepG2 cells predominantly express the type II interleukin 1 receptor (biochemical and molecular characterization of the IL-1 receptor).

In this study we have characterized the cell surface interleukin 1 (IL-1) receptor in HepG2 hepatoma cells. We found that HepG2 cells bind both IL-1 alpha and beta with high affinity, KDs of 136 and 180 pM and receptor densities of 16,000 and 8500 binding sites/cell respectively. The binding sites appeared to be predominantly type II since phorbol ester treatment of the cells, which selectively downregulates type II IL-1 receptors, reduced binding by 68% while treatment of the cells with an inhibitory monoclonal antibody specific for the type I receptor had no significant effect on IL-1 binding. Competition studies with a modified IL-1 beta analog (Glu4) also revealed binding kinetics more consistent with binding to type II receptors than to type I. Crosslinking and ligand blotting with human 125I-IL-1 demonstrated the presence of two bands, a 78 kDa band typical of crosslinking to type II (p60) receptor, and a 98 kDa band, typical of crosslinking to the type I (p80) receptor. Low level expression of the type I receptor was consistent with molecular biological studies employing polymerase chain reaction (PCR) amplification which indicated that mRNA for the type I receptor was produced by the HepG2 cells. Functional receptors were demonstrated by the induction of IL-8 by IL-1 stimulated cells.

Animals↗
PubMed1992

Prescriptive hearing aid fitting by parameter adjustment and selection.

We describe the rationale for the development of a psychophysical procedure that allows individual listeners to adjust the frequency-gain characteristic of a programmable hearing aid on a unidimensional scale, based on a target-gain reference value. The listener's task is to adjust the frequency response and select the parametric value judged to optimize the intelligibility or quality of speech. Originally described as the Sliding Scale, the procedure has been modified for use in reliability and validity studies of hearing aid fitting at Michigan State University. The modified approach is referred to as the Parameter Adjustment and Selection (PAS) procedure. Primary immediate goals for the procedure are ease of use, high reliability, and rapid clinical administration. The procedure, which may offer potential advantages over a paired-comparison approach, appears to be generally applicable to the fitting of digitally programmable hearing aids.

Auditory Threshold↗
PubMed1989

Activation by saccharides of a cation-selective pathway on canine lingual epithelium.

Responses of isolated canine lingual epithelium in an Ussing chamber to D-glucose and fructose reveal events associated with taste transduction. With the use of isotopic flux studies, together with ion substitution and pharmacological and voltage clamp measurements, it was found that the stimulation of ion transport by D-glucose arises from an increase in the influx of cations through a cation-selective pathway. This influx of cations is completely inhibited by 0.1 mM amiloride. The stimulation of transport by fructose in 0.05 M KCl and by D-glucose in 0.05 M RbCl was also inhibited by amiloride, demonstrating that the saccharide-stimulated entry pathway was specific for neither hexose sugars nor for Na. Saccharide stimulation of canine lingual epithelia does not appear to be modulated by increases in intracellular levels of adenosine 3',5'-cyclic monophosphate, guanosine 3',5'-cyclic monophosphate, or Ca. The Na that enters taste cells on saccharide stimulation exits them via the ouabain inhibitable Na+-K+-adenosinetriphosphatase located in the serosal membranes.

Amiloride↗
PubMed1988

Transport pathways in rat lingual epithelium.

Measurements of ion transport across isolated lingual epithelium of rat were correlated with electrophysiological recordings from taste nerves. At hyperosmotic concentrations of NaCl, sodium ions enter the mucosal membrane of the isolated epithelium partially through an amiloride-inhibitable pathway and exit the serosal membrane through a Na+-K+-ATPase. At hyposmotic concentrations of KCl, potassium ions enter the mucosal membrane through a K+ pathway that is inhibited by 4-aminopyridine and exit at the serosal membrane through a K+ pathway that is inhibited by BaCl2. The inhibition of sodium transport by amiloride and potassium transport by 4-aminopyridine is consistent with previously published electrophysiological recordings from the chorda tympani nerve bundle (CT) and recordings from nucleus of the solitary tract (NST) obtained here. The responses to NaCl are greater than the responses to KCl at equimolar concentrations over the entire concentration range both in epithelial and neural measurements. At hyposmotic concentrations of NaCl the epithelial responses include inward sodium and outward chloride components. Isolated rat tongue is only slightly stimulated by D-glucose or sucrose as are the CT and NTS responses. These data suggest that events in taste transduction can be understood, in part, by measuring the epithelial responses of isolated rat tongue.

4-Aminopyridine↗
PubMed1988

Spatial map of salts and saccharides on dog tongue.

Front and rear regions of dog tongue were tested for spatial heterogeneity with respect to monovalent chloride salts (NaCl, KCl, and NH4Cl) and sweet tastants (sucrose, D-glucose, and L-glucose) by placing them in Ussing chambers where the open-circuit potential, Voc, and short-circuit current, Isc, were measured. The responses of Voc and Isc to 0.5 M NaCl were greater in the front of the tongue than in the rear, whereas the responses of Voc and Isc to 0.5 M sucrose were greater in the rear of the tongue than in the front. These results are similar to those of published neurophysiological measurements from the chorda tympani nerve and thalamus. These data suggest that the spatial heterogeneities seen in higher taste centers are present in the isolated lingual epithelium where primary taste transduction events occur.

Ammonium Chloride↗
PubMed1987

Autocrine growth of T cells independent of interleukin 2: identification of interleukin 4 (IL 4, BSF-1) as an autocrine growth factor for a cloned antigen-specific helper T cell.

Interleukin 4 (IL 4), formerly known as B cell stimulatory factor 1 (BSF-1), has recently been described as a growth factor for T cells. The role of IL 4 in the putatively IL 2-independent growth of certain cloned T helper cells is unclear. D10.G4.1 (D10) is a conalbumin-specific helper T cell that has been employed extensively in the analysis of T cell activation and as an assay for the detection of IL 1. Previously, it was thought that IL 1 induced the expression of IL 2 receptors on D10 cells, thereby permitting D10 to proliferate in response to endogenously produced IL 2. However, we cannot detect IL 2 mRNA or protein in D10 cells or their supernatants as determined by the following criteria: monoclonal antibodies that neutralize the in vitro activity of murine IL 2 do not block the IL 1-dependent proliferation of D10 cells; no competitive binding for high-affinity IL 2 receptors with 125I-labeled IL 2 can be detected with medium conditioned by activated D10 cells; and Northern blot analysis and S1 nuclease protection assays, performed with cDNA probes for IL 2, do not detect mRNA for IL 2 under a variety of different activation conditions that foster autocrine growth of D10 cells. In contrast, activated D10 cells produce both IL 4 mRNA and protein as judged by similar criteria. Purified IL 4 has significant TCGF activity as measured by proliferation of HT-2 cells. This activity can be blocked completely by a monoclonal antibody to IL 4 (11B11). The proliferation of D10 cells in the presence of 3D3 (a clonotype-specific monoclonal anti-T cell receptor antibody) and IL 1 can be blocked completely by 11B11 antibody. Highly purified IL 4 alone cannot induce the proliferation of resting D10 cells; however, equivalent amounts of IL 4 in the presence of recombinant IL 1 induce significant D10 proliferation. Therefore, IL 1 appears to render D10 cells responsive to their autocrine growth signal. These data indicate that IL 4 serves as the autocrine T cell growth factor for D10 cells, and that exogenous IL 1 is required for the transduction of this growth signal. This may represent a more broadly applicable mechanism for the growth of certain subsets of T helper cells.

Animals↗
PubMed1986

Epithelial responses of rabbit tongues and their involvement in taste transduction.

The response of rabbit tongue, placed in a modified Ussing chamber, to salts [KCl, NaCl, NH4Cl, tetraethylammonium chloride (TEACl)], sweeteners (D-glucose, sucrose), acid (HCl), and a bitter tastant, quinine, was investigated for the first time. These experiments were conducted to further explore the new paradigm of taste transduction that correlates changes in the electrical behavior of lingual epithelia with neural responses. In addition, the responses of rabbit tongue data were compared with previously published data on dog and frog tongues. When increases in short-circuit current (Isc) for rabbit tongue induced by hyperosmotic concentrations of several salts were compared, the following sequence was found: KCl greater than NH4Cl greater than NaCl greater than TEACl. These results are consistent with previously published integrated chorda tympani responses (ICTR) as well as behavioral studies that showed that rabbits prefer KCl to NaCl with their natural diet. Pharmacological studies using ouabain and amiloride suggest that K and Na are traversing rabbit tongue through different pathways. The maximal stimulation of Isc by D-glucose and sucrose (in 50 mM NaCl) was significantly smaller than those measured for KCl and NaCl. The rabbit tongue was sensitive to HCl at concentrations less than 1 mM in agreement with ICTR measurements.

Animals↗
PubMed1986

Transorbital penetrating injuries to the frontal lobe.

Three cases of transorbital penetrating trauma to the frontal lobe are reported. These cases are remarkable in that minimal ocular trauma was incurred and excellent vision was preserved. These cases underscore the importance of suspecting the possibility of intracranial injury when evaluating penetrating orbital trauma.

Adolescent↗
PubMed1984

A suspension model for hypokinetic/hypodynamic and antiorthostatic responses in the mouse.

Hypokinetic/hypodynamic and antiorthostatic responses to weightlessness and bedrest were simulated in mice using a suspension technique. Animals were suspended for 1 or 2 weeks in an antiorthostatic posture and positioned to permit freedom of movement but eliminate load bearing by the hindlimbs. Suspended mice exhibited reduced food and water intakes and rapid 10% decrease in body weight to a level which was maintained for the remainder of the suspension period. Diuresis was evident in suspended mice, but the natriuresis and kaliuresis previously observed in the suspended rat were not evident. Differential hindlimb muscle atrophy (soleus greater than plantaris = gastrocnemius greater than EDL) and increased excretion of urea and ammonia were also noted in suspended mice. Postsuspension recovery studies indicated that the recovery process was highly effective. These results document specific responses to hypokinesia/hypodynamia and antiorthostasis in the mouse and demonstrate similarities in the responses of mice and rats to suspension. These studies expand the utility of the suspension model and suggest that the mouse may be useful in future studies simulating both weightlessness and bedrest.

Adrenal Glands↗