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Biomedical subjects

A M Bell

Publications and source records attributed to A M Bell.

At least 19 recordsLinked to original sources
PubMed2007

Severe citrate toxicity complicating volunteer apheresis platelet donation.

We report a case of severe citrate toxicity during volunteer donor apheresis platelet collection. The donor was a 40-year-old female, first-time apheresis platelet donor. Past medical history was remarkable for hypertension, hyperlipidemia, and depression. Reported medications included bumetanide, pravastatin, and paroxetine. Thirty minutes from the start of the procedure, the donor noted tingling around the mouth, hands, and feet. She then very rapidly developed acute onset of severe facial and extremity tetany. Empirical treatment with intravenous calcium gluconate was initiated, and muscle contractions slowly subsided over approximately 10 to 15 minutes. The events are consistent with a severe reaction to calcium chelation by sodium citrate anticoagulant resulting in symptomatic systemic hypocalcemia. Upon additional retrospective analysis, it was noted that bumetanide is a loop diuretic that may cause significant hypocalcemia. We conclude that careful screening for medications and underlying conditions predisposing to hypocalcemia is recommended to help prevent severe reactions due to citrate toxicity. Laboratory measurement of pre-procedure serum calcium levels in selected donors may identify cases requiring heightened vigilance. The case also illustrates the importance of maintaining preparedness for managing rare but serious reactions in volunteer apheresis blood donors.

Adult↗
PubMed2005

Behavioural differences between individuals and two populations of stickleback (Gasterosteus aculeatus).

Behavioural syndromes are correlations between behaviours in different functional contexts. Behavioural syndromes are attracting the attention of evolutionary biologists because they mean that different behaviours might not be free to evolve independently of one another. In a landmark study, Huntingford (1976) showed that individual stickleback which were bold toward predators were also aggressive toward conspecifics and active in an unfamiliar environment. Here, I revisited the activity-aggression-boldness syndrome in stickleback and tested the hypothesis that correlations between behaviours might act as evolutionary constraints. I measured a suite of behaviours on wild-caught individuals and their offspring from two different populations and calculated heritabilities and genetic correlations between the different behaviours. I found that these behaviours were phenotypically and genetically correlated in one population but not another. On average, boldness and aggression were negatively related to each other across the populations. These results suggest that behavioural syndromes don't always act as evolutionary constraints.

Aggression↗
PubMed2001

Chemically induced magnetism and magnetoresistance in La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4).

It is shown by magnetometry and microSR spectroscopy that short-range magnetic interactions between the Mn cations in the nonmetallic K(2)NiF(4)-like phase La(0.8)Sr(1.2)Mn(0.6)Rh(0.4)O(4) become significant below approximately 200 K. Negative magnetoresistance (rho/rho(0) approximately 0.5 in 14 T at 108 K) is apparent below this temperature. Neutron diffraction has shown that an applied magnetic field of 5 T is sufficient to induce saturated (3.38(7)mu(B) per Mn) long-range ferromagnetic ordering of the atomic moments at 2 K, and that the induced ordering persists up to a temperature of 50 K in 5 T. Spin glass behavior is observed below 20 K in the absence of an applied field. The induced magnetic ordering is attributed to the subtle changes in band structure brought about by the external field, and to the controlling influence of Rh(3+) over the relative strength of competing magnetic exchange interactions.

Journal Article↗
PubMed2000

Vanilloid receptor-related osmotically activated channel (VR-OAC), a candidate vertebrate osmoreceptor.

The detection of osmotic stimuli is essential for all organisms, yet few osmoreceptive proteins are known, none of them in vertebrates. By employing a candidate-gene approach based on genes encoding members of the TRP superfamily of ion channels, we cloned cDNAs encoding the vanilloid receptor-related osmotically activated channel (VR-OAC) from the rat, mouse, human, and chicken. This novel cation-selective channel is gated by exposure to hypotonicity within the physiological range. In the central nervous system, the channel is expressed in neurons of the circumventricular organs, neurosensory cells responsive to systemic osmotic pressure. The channel also occurs in other neurosensory cells, including inner-ear hair cells, sensory neurons, and Merkel cells.

Amino Acid Sequence↗
PubMed2000

A novel conserved cochlear gene, OTOR: identification, expression analysis, and chromosomal mapping.

We have identified a novel cochlear gene, designated OTOR, from a comparative sequence analysis of over 4000 clones from a human fetal cochlear cDNA library. Northern blot analysis of human and chicken organs shows strong OTOR expression only in the cochlea; very low levels are detected in the chicken eye and spinal cord. Otor and Col2A1 are coexpressed in the cartilaginous plates of the neural and abneural limbs of the chicken cochlea, structures analogous to the mammalian spiral limbus, osseous spiral lamina, and spiral ligament, and not in any other tissues in head and body sections. The human OTOR gene localizes to chromosome 20 in bands p11.23-p12.1 and more precisely to STS marker WI-16380. We have isolated cDNAs orthologous to human OTOR in the mouse, chicken, and bullfrog. The encoded protein, designated otoraplin, has a predicted secretion signal peptide sequence and shows a high degree of cross-species conservation. Otoraplin is homologous to the protein encoded by CDRAP/MIA (cartilage-derived retinoic acid sensitive protein/melanoma inhibitory activity), which is expressed predominantly by chondrocytes, functions in cartilage development and maintenance, and has growth-inhibitory activity in melanoma cell lines.

Animals↗
PubMed2000

Identification with a recombinant antibody of an inner-ear cytokeratin, a marker for hair-cell differentiation.

Extensive biochemical characterization of cells in the inner ear has been hampered by a lack of tools with which to identify inner-ear proteins. By using a single-chain antibody fragment isolated from a bacteriophage-displayed library, we have identified a cytokeratin that is abundant in nonsensory cells of the frog inner ear. Although the progenitors of hair cells exhibit strong immunoreactivity to this cytokeratin, the signal declines in immature hair cells and vanishes as the cells mature. The correlation between diminished immunoreactivity and hair-cell differentiation indicates that the cytokeratin is down-regulated during the transition from a nonsensory to a sensory cell and suggests that the marker is an early index of hair-cell differentiation.

Amino Acid Sequence↗
PubMed1998

Localization of a gene for otosclerosis to chromosome 15q25-q26.

Among white adults otosclerosis is the single most common cause of hearing impairment. Although the genetics of this disease are controversial, the majority of studies indicate autosomal dominant inheritance with reduced penetrance. We studied a large multi-generational family in which otosclerosis has been inherited in an autosomal dominant pattern. Five of16 affected persons have surgically confirmed otosclerosis; the remaining nine have a conductive hearing loss but have not undergone corrective surgery. To locate the disease-causing gene we completed genetic linkage analysis using short tandem repeat polymorphisms (STRPs) distributed over the entire genome. Multipoint linkage analysis showed that only one genomic region, on chromosome 15q, generated a lod score >2.0. Additional STRPs were typed in this area, resulting in a lod score of 3.4. STRPs FES (centromeric) and D15S657 (telomeric) flank the 14. 5 cM region that contains an otosclerosis gene.

Adult↗
PubMed1997

Fatal human melioidosis in south-eastern Queensland.

Two simultaneous human cases of fatal melioidosis in temperate south-eastern Queensland involved patients who had had pre-existing multisystem illnesses, had sustained cutaneous lesions before illness onset, and died from overwhelming sepsis. Onset of disease was preceded by unseasonably heavy rainfall. These and other features of these cases suggest that the source of infection was local, in which case the endemicity of Burkholderia pseudomallei in temperate regional Australia may be broader than is currently recognised, and melioidosis may need to be considered in at-risk patients in these areas, as well as in tropical and subtropical areas, who present with severe pneumonia and septicaemia.

Acute Disease↗
PubMed1994

Deletion (11)(q14.1q21).

We report on a 4-year-old girl with moderate developmental delay, horseshoe kidney, bilateral duplication of the ureters with right upper pole obstruction, hydronephrosis and nonfunction, and subsequent Wilms tumor of the right lower pole. She had an interstitial deletion of the long arm of chromosome 11 involving the region 11(q14.1q21).

Abnormalities, Multiple↗
PubMed1994

Sexual maturation in male prairie voles: effects of the social environment.

The effects of various social contexts on sexual maturation in captive male prairie voles were investigated. Sexual maturity was assessed as the ability of a young male to produce urine capable of activating a diestrous adult female into estrus, as females remain anestrus until they ingest a male urinary chemosignal. In five experiments the postweaning social environments of developing males were manipulated (e.g., presence or absence of dam, sire, or junior litter, exposure to unfamiliar adult voles, social isolation) to determine if the age at which males begin to produce potent urine was sensitive to social effects. In general, there was no difference in the age of potent urine production as a function of social environment. Findings are discussed in the context of dispersal, inbreeding avoidance, and mate acquisition.

Animals↗
PubMed1994

Ongoing results of excimer laser photorefractive keratectomy for myopia: subjective patient impressions.

We present the results of a survey carried out by independent researchers to determine the subjective success rate of a series of excimer laser photorefractive keratectomy procedures to correct myopia. Thirty patients, selected at random from a group of 300, had received treatment to both eyes with a minimum of six months follow-up on the second eye. Forty-four patients, selected at random from a group of 120, had received treatment to one eye only with five months of follow-up. The results show a high level of satisfaction with the results of the procedure.

Adult↗
PubMed1993

Fecal short-chain fatty acid concentrations and effect on ileal pouch function.

Random stool samples were obtained from 14 ileal pouch-anal anastomosis (IPAA) patients 43 +/- 5 (mean +/- SEM) months after surgery, and the concentrations of individual short-chain fatty acids (SCFAs) were determined by gas liquid chromatography. Stool frequency was determined from a diary recorded for 15 days prior to stool sampling. The frequency, amplitude, and duration of phasic contractions (PCs) within the pouch following infusion of a physiologic concentration of SCFAs and normal saline randomly into the pouch of six IPAA patients were determined manometrically. The mean total SCFA concentration after IPAA did not differ significantly from normal stools (83 +/- 20 mM after IPAA vs. 97 +/- 10 mM for controls; P > 0.05). In the IPAA patients, regression analysis demonstrated an inverse relationship between stools per day and total SCFA concentration (r = 0.73; P < 0.001). Moreover, no change in frequency (3.0 +/- 0.9 vs. 3.2 +/- 0.8 PCs/30 minutes), amplitude (26 +/- 5 vs. 25 +/- 4 mmHg), or duration (23 +/- 3 vs. 26 +/- 2 seconds) of PCs was found after SCFA infusion compared with saline control (P > 0.1). These findings demonstrate that SCFAs are present in ileal pouch effluent and that stool frequency may be related to fecal SCFA concentration. Also, the normal contractile response of the terminal ileum to SCFAs does not occur in the ileal pouch.

Adult↗
PubMed1993

Rectal wall contractility in healthy subjects and in patients with chronic severe constipation.

OBJECTIVE: The aim of this study was to identify differences in rectal wall contractility between healthy volunteers and patients with chronic severe constipation. SUMMARY BACKGROUND DATA: Whether motor function of the rectum contributes to slow-transit constipation is unknown. Measurements of rectal contractility have been performed traditionally with perfused catheters or microtransducers. The rectal barostat is a new technique that quantifies the volume of air within an infinitely compliant intrarectal bag maintained at constant pressure; decreases in bag volume therefore reflect increases in rectal muscular contractility (tone). Increases in volume reflect decreased contractility. METHODS: Fifteen healthy volunteers (ten women and five men; mean age, 36 years) and eight patients (seven women and one man; mean age, 44 years) were studied. Barostat recordings were made for 1 hour before and after a meal. Randomly, neostigmine (0.5 mg) or glucagon (1 unit) was then given intravenously. After 1 hour, the other medication was given. RESULTS: The fasting rectal volume was similar in the patient and control groups (113 +/- 7 mL vs. 103 +/- 4 mL, respectively; p > 0.05). Compared with controls, constipated patients had a significantly lower reduction in rectal volume after a meal (constipated, 35 +/- 8% vs. controls, 65 +/- 7%; p < 0.05) and after neostigmine administration (constipated, 39 +/- 6% vs. controls, 58 +/- 6%; p < 0.05). Moreover, constipated patients had a smaller increase in rectal volume after glucagon administration than did controls (28 +/- 6% vs. 64 +/- 18%, respectively; p < 0.05. CONCLUSIONS: Changes in rectal wall contractility in response to feeding, a cholinergic agonist, and a smooth muscle relaxant were decreased in constipated patients. These findings suggest that an abnormality of rectal muscular wall contractility is present in constipated patients.

Adult↗
PubMed1991

The effect of stool consistency on rectal and neorectal emptying.

Although stool consistency is considered to be an important component of anorectal continence, its effect on rectal emptying has never been quantitated. In 12 healthy volunteers and 12 patients after ileal pouch-anal anastomosis (IPAA) (46 +/- 5 months after the operation; mean +/- SEM), perfused anal manometry was performed; movements of the anorectal angle were quantitated scintigraphically; and rectal capacity and compliance were measured by air insufflation of an intrarectal balloon at three infusion rates. The efficiency of rectal evacuation of three consistencies (5 percent, liquid; 7.5 percent semisolid gel; 11.25 percent solid gel; w/w) of Tc99m labeled artificial stool (aluminum magnesium silicate gel) was quantitated by gamma camera imaging. No abnormalities of pelvic floor function were demonstrated in either controls or patients. The mean neorectal capacity and compliance of patients with IPAA did not differ from control, (capacity; IPAA: 215 +/- 22 ml vs. control; 245 +/- 29 ml; compliance; IPAA: 5.5 +/- 0.7 ml/cm H2O vs. control; 6.6 +/- 0.7 ml/cm H2O; P greater than 0.05). In controls, the percentage of the 7.5 percent consistency evacuated (81 +/- 5 percent, mean +/- SEM) was significantly more than the percentage evacuation of either the 5 percent consistency (67 +/- 7 percent) or the 11.25 percent consistency (77 +/- 2 percent) (P less than 0.05). After IPAA, the mean overall percent evacuation of the three stool consistencies was significantly less than control (52 +/- 6 percent after IPAA; 75 +/- 5 percent control, P less than 0.05). However, there was no significant difference in neorectal emptying between the liquid, the semisolid gel and the solid gel (56 +/- 6, 55 +/- 6, 51 +/- 9 percent, respectively, P greater than 0.1). We concluded that in healthy subjects but not in patients after IPAA, stool consistency affected the efficiency of evacuation of enteric content.

Adult↗
PubMed1991

Variations in muscle tone of the human rectum: recordings with an electromechanical barostat.

Rectal wall tone (the contractile state of the rectal tunica muscularis) should mediate accommodation and influence rectal emptying. Such changes in tone however can be only inferred from changes in baseline pressure recorded with conventional manometry. We used an isobaric volumetric device, the rectal electromechanical barostat, to quantify variations in tone of the rectal wall in response to feeding and to perturbations in response to the pharmacological agents neostigmine and glucagon. The barostat quantitates muscular wall tone indirectly by measuring its reciprocal, e.g., the volume of air within a flaccid intraluminal bag that is maintained at a constant and preselected pressure, by an electronic feedback mechanism. The barostat as well as a three-channel perfused manometric catheter were positioned in the rectum of 14 healthy volunteers. Three patterns of changes were observed: 1) respiratory fluctuations, 2) rapid volume waves, and 3) slow volume changes. Rectal tone varied little during fasting; rapid or slow changes in intrabag volume were infrequent. Ingestion of a standard meal was followed by a significant decrease in barostat bag volume (85 +/- 6 ml fasting vs. 50 +/- 8 ml fed, P less than 0.05). Pharmacological agents also induced predictable responses; neostigmine decreased bag volume and induced phasic pressure activity, whereas glucagon abolished phasic pressure activity and increased barostat bag volume. Perfused manometric catheters showed no concomitant changes in baseline pressure. We concluded that a rectal barostat measured variations in human rectal tone, which were not recorded by conventional manometric techniques. These changes in rectal tone might have important functional significance.

Adult↗
PubMed1991

Dentistry is making a career comeback.

Technology took some of the bloom off dentistry as a career choice. Ironically, it's the same force that has given new status to the profession and made dentistry the career of the future.

Career Choice↗