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Biomedical subjects

B L Smith

Publications and source records attributed to B L Smith.

At least 145 records · Page 8Linked to original sources
PubMed1994

External quality assessment of techniques for the detection of drugs of abuse in urine.

Five chromatographic and six immunoassay techniques were compared using data reported by 131 participants in the UK National External Quality Assessment Scheme for Drugs of Abuse in Urine. Twenty five samples were studied containing none or one of three concentrations of amphetamine, barbiturates, benzodiazepines, benzoylecgonine, methadone and morphine. Technique sensitivity and specificity achieved with realistic clinical samples of 25 mL vol were assessed as the percentage of true positive and true negative tests, respectively. Thin-layer chromatography was inadequate for the detection of several analytes, the sensitivity for 0.5 mg/L of benzoylecgonine being < 30%, and for 1.5 mg/L of amphetamine < 86%. Gas chromatography with mass spectrometry was significantly less sensitive than other techniques for the detection of 0.5 mg/L of benzoylecgonine (71%) and 1.5 mg/L of morphine (88%). High-performance liquid chromatography was the most sensitive for amphetamine. Immunoassays performed well when operating above their specified cut-off concentrations but, because they are directed to quinalbarbitone showed reduced cross-reactivity with amylobarbitone, the barbiturate more commonly prescribed in the UK.

Chromatography↗
PubMed1994

Center-based vs patient-based diagnosis and therapy of sleep-related respiratory disorders and the role of the respiratory care practitioner.

Unlike center-based laboratories that follow prescribed technical standards, patient-based studies lack technical standardization. Whereas center-based studies are usually performed by technicians who have met certain professional criteria, patient-based studies can be performed by anyone, even those without clinical training. Although guidelines are currently being developed to direct the use of unattended monitoring in the home, a need exists for specific guidelines that delineate professional qualifications for those who initiate and titrate therapy for patients with sleep-related respiratory disorders. The opportunity exists for respiratory care practitioners to become involved with creating guidelines for patient monitoring and therapeutic intervention, in both center-based and patient-based settings. A need exists for multicenter, peer-reviewed, controlled studies to establish standard recording variables and machine specifications for unattended monitoring devices. Also, the role and cost-benefit ratio of unattended monitoring in healthcare delivery need to be defined. Therefore, with the demand for technology-oriented research, clinical outcome studies, and professional standards, more respiratory care practitioners have the opportunity to expand their practice into the field of sleep medicine.

Allied Health Personnel↗
PubMed1994

Localization of aquaporin CHIP in the human eye: implications in the pathogenesis of glaucoma and other disorders of ocular fluid balance.

PURPOSE: The existence of integral membrane proteins that serve as selective water channels has been postulated to explain the movement of water across plasma membranes. Aquaporin CHIP (channel-forming integral membrane protein of 28 kd) is the first such channel to be characterized and is abundant in human erythrocytes and a variety of secretory and absorptive epithelia of the rat. Because disturbances in the movement of water characterize several ocular diseases, the distribution of CHIP in the human eye was studied. METHODS: Affinity-purified antibodies against purified CHIP protein were used for the indirect immunofluorescence localization of CHIP in human eye structures. Labeling was confirmed by immunoblot analyses of membrane preparations from eye structures. RESULTS: CHIP immunolabeling was found in the corneal endothelium, the lens epithelium, the nonpigmented epithelium of the ciliary process, the iris epithelium, and the endothelium of the trabecular meshwork and the canal of Schlemm. CONCLUSIONS: The presence of CHIP water channels in the secretory and absorptive tissues of the human eye provides a mechanism for transcellular water movement and may be important for understanding diseases of the eye that involve excess or insufficient movement of ocular fluid such as glaucoma, cataracts, and Fuch's dystrophy. In addition, the existence of CHIP in the outflow pathways of the human eye provides a novel explanation for the movement of water out of the eye.

Adolescent↗
PubMed1994

Concentration of ptaquiloside, a major carcinogen in bracken fern (Pteridium spp.), from eastern Australia and from a cultivated worldwide collection held in Sydney, Australia.

Two surveys of bracken fern for the concentration of the carcinogen ptaquiloside (PT) have been carried out, one of bracken fern from the eastern side of Australia and the other from a worldwide collection of bracken clones held in Sydney Australia. Bracken from eastern Australia contained concentrations of ptaquiloside ranging from 0 to 12,945 micrograms PT/g. From 91 samples 15% contained greater than 5,000 micrograms PT/g and 57% of samples contained more than 1,000 micrograms PT/g bracken on the dry weight basis. Ptaquiloside concentrations were highest in Pteridium revolutum and from P. esculentum from areas where bovine enzootic haematuria was known to occur. Bracken from the cultivated bracken clone collection from world-wide sources tended to have lower concentrations of ptaquiloside ranging from 0 to 9,776 micrograms PT/g. From 77 samples, 8% contained more than 5,000 micrograms PT/g and 35% contained more than 1,000 micrograms PT/g bracken. Samples from both the eastern Australia survey and the Australian representatives in the worldwide collection showed significantly higher concentrations of PT in the P. esculentum collected from the more southern states. In samples from the worldwide collection there were no statistical differences in the concentrations of PT in bracken between taxa.

Analysis of Variance↗
PubMed1994

Adenylate levels and environmental stress in the sea anemone Anthopleura elegantissima.

The tissue concentrations of adenosine nucleotides in the sea anemone Anthopleura elegantissima were determined during laboratory manipulations simulating natural environmental stresses: desiccation at low and high air temperatures, increased seawater temperature, mechanical disturbance causing column contraction, and starvation. The levels of adenylates significantly decreased during anemone desiccation, column contraction, and starvation. Variations in adenylate energy charge, the ratio of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) and the ratio of ATP to total adenylates were compared with changes in absolute adenylate concentrations to determine the usefulness of these ratios in indicating changes in metabolic activity and physiological stress. The changes in the adenylate levels were far greater than the changes in adenylate ratios. The usefulness of adenylate energy charge, or the other adenylate ratios, as single or exclusive indices of metabolic stress in A. elegantissima is questionable, given these results. Changes in absolute adenylate levels do indicate significant metabolic changes in the anemones associated with desiccation, column contraction, and starvation.

Adenosine Diphosphate↗
PubMed1994

Effect of body direction on heart rate in trailered horses.

To determine whether body direction in a trailer affects the degree to which a horse is excited (and presumably stressed) during transport, heart rates were measured in 8 Thoroughbred geldings transported over a 32-km route of county roads while tethered facing forward or backward in a 4-horse stock trailer. Heart rates also were measured on the horses while they were tethered facing forward or backward in the same trailer while it was parked. Heart rates decreased during the first 10 minutes for both groups, and remained stable after the first 15 minutes. Heart rates were not significantly different between horses facing forward or backward during transport or while parked. Heart rates were significantly (P < 0.05) higher for horses during transport, compared with those of horses in a parked trailer whether facing forward or backward.

Animals↗
PubMed1994

Evaluation of a technique for detection of pulmonary hemorrhage in horses, using carbon monoxide uptake.

The diffusing capacity for carbon monoxide (DLCO) and the functional residual capacity (FRC) of the lung were measured in 5 healthy Thoroughbreds before and after instillation of autologous blood into their lungs, in an attempt to develop a method to quantitate extravascular blood in the lungs of horses with exercise-induced pulmonary hemorrhage. Mean (+/- SD) baseline values of DLCO and FRC were 333.8 +/- 61.9 ml/min/mm of Hg and 21.464 +/- 4.156 L, respectively. Blood instillation resulted in decreases in DLCO and FRC. The paradoxic decrease in DLCO (we were expecting to find an increase owing to blood in the airspaces, as has been reported in people) appears to be associated with the bronchoscopic procedure and with presence of blood in the airways. We concluded that rebreathing DLCO measurements were not effective for detecting blood introduced bronchoscopically into the lungs of horses.

Animals↗
PubMed1993

Covalent binding of the carcinogen benzo[a]pyrene diol epoxide to Xenopus laevis 5 S DNA reconstituted into nucleosomes.

The sequence-specific interactions of bulky carcinogens with purified DNA might reasonably be expected to be altered when the DNA is organized into chromatin. We have approached this subject by studying the covalent binding of a potent carcinogen, 7r,8t-dihydroxy-9t,10t-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE-I) to nucleosomal and free DNA, using a defined fragment of DNA derived from the 5'-end of the 5 S rRNA gene of Xenopus laevis, reconstituted into nucleosomes by salt exchange with unlabeled chicken mononucleosomes. Micrococcal nuclease and hydroxyl radical "footprinting" experiments demonstrated the formation of a uniquely positioned nucleosome covering the transcriptional start point of the gene. The reconstituted nucleosomes or control DNA samples were modified with BPDE-I. DNA was repurified from the nucleosomal and control modification reactions and then irradiated with laser light at 355 nm, causing strand breaks at the positions of adducts. Nucleosomal DNA exhibited a marked decrease in the level of carcinogen binding, especially in the central 80-90 base pairs of the nucleosomal region. Interestingly, although overall binding was inhibited about 2-fold, the sequence-specific pattern of binding to deoxyguanosine residues seen with purified DNA was maintained in the nucleosomal DNA.

Animals↗
PubMed1993

Distribution of the aquaporin CHIP in secretory and resorptive epithelia and capillary endothelia.

The existence of water-selective channels has been postulated to explain the high water permeability of erythrocytes and certain epithelial cells. The aquaporin CHIP (channel-forming integral membrane protein of 28 kDa), a molecular water channel, is abundant in erythrocytes and water-permeable segments of the nephron. To determine whether CHIP may mediate transmembrane water movement in other water-permeable epithelia, membranes of multiple organs were studied by immunoblotting, immunohistochemistry, and immunoelectron microscopy using affinity-purified anti-CHIP IgG. The apical membrane of the choroid plexus epithelium was densely stained, implying a role for CHIP in the secretion of cerebrospinal fluid. In the eye, CHIP was abundant in apical and basolateral domains of ciliary epithelium, the site of aqueous humor secretion, and also in lens epithelium and corneal endothelium. CHIP was detected in membranes of hepatic bile ducts and water-resorptive epithelium of gall bladder, suggesting a role in bile secretion and concentration. CHIP was not detected in glandular epithelium of mammary, salivary, or lacrimal glands, suggesting the existence of other water-channel isoforms. CHIP was also not detected within the epithelium of the gastrointestinal mucosa. CHIP was abundant in membranes of intestinal lacteals and continuous capillaries in diverse tissues, including cardiac and skeletal muscle, thus providing a molecular explanation for the known water permeability of certain lymphatics and capillary beds. These studies underscore the hypothesis that CHIP plays a major role in transcellular water movement throughout the body.

Animals↗
PubMed1993

Developmental gene expression and tissue distribution of the CHIP28 water-channel protein.

The CHIP28 water channel is a major component of red cell and renal tubule membranes; however, its ontogeny and tissue distribution remain undefined. Three patterns of expression were identified when CHIP28 mRNA was surveyed by in situ hybridization histochemistry in rats between embryonic day 14 and maturity. (i) CHIP28 mRNA and protein were very abundant in hematopoietic tissue and kidneys of mature rats, but strong expression did not occur until after birth, when it appeared in renal proximal tubules and descending thin limbs, red pulp of the spleen, and membranes of circulating red cells. (ii) CHIP28 mRNA was abundant in choroid plexus epithelium throughout fetal development and maturity. (iii) CHIP28 mRNA was transiently observed in periosteum, heart, vascular endothelium, and cornea during fetal development. The ontogeny of kidney and red cell CHIP28 expression coincides with the ability of kidneys to concentrate urine, suggesting that CHIP28 promotes water reabsorption in the proximal nephron and provides red cell osmoregulation needed for passage through the hypertonic medulla. Its presence in the choroid plexus suggests that CHIP28-mediated water transport contributes to secretion of cerebrospinal fluid. The functional role of CHIP28 in developing bone, heart, and eye is unclear. These findings further establish the general physiologic role of CHIP28 as a water channel involved in reabsorption, osmoregulation, and secretion. The studies also suggest other possible functions during fetal development and predict that complex mechanisms will be needed for regulation of CHIP28 gene expression in diverse tissues at distinct points in development.

Animals↗
PubMed1993

Congenital scalp defects and vitreoretinal degeneration: redefining the Knobloch syndrome.

An apparently autosomal recessive syndrome of hereditary vitreoretinal degeneration (VRD) with retinal detachment, high myopia, and congenital encephalocele was described in 1971 by Knobloch and Layer [J Pediatr Ophthalmol 8:181-184]. Clinical confirmation of the presence of encephaloceles was lacking, and no neuropathologic studies were reported. We have evaluated a similarly affected family with 2 sibs with high myopia, VRD, and occipital scalp defects. Histologic examination of the scalp defects showed heterotopic neuronal tissue in both instances. The older girl has had a unilateral retinal detachment. Her other eye and both eyes of the younger sib have so far been treated successfully with prophylactic retinal cryotherapy. Both children have normal to above normal intelligence. The family reported by Knobloch and Layer [1971] and the sibship herein described appear to represent a distinct autosomal recessive trait. Analysis of the associated defects suggests an underlying defect in early cephalic neuroectodermal morphogenesis. Data from these families imply that congenital occipital scalp defects rather than true encephaloceles may, as is true in some cases of Meckel syndrome, accompany Knobloch syndrome. The presence of a congenital midline scalp defect should alert the clinician to possible underlying central nervous system and/or ocular pathology and should lead to consideration of further diagnostic evaluations and prophylactic measures.

Child↗
PubMed1993

Multicenter trial of fleroxacin versus ceftriaxone in the treatment of uncomplicated gonorrhea.

In a multicenter, randomized, open, comparative trial, patients with uncomplicated gonorrhea were treated with 400 mg of oral fleroxacin or 250 mg of intramuscular ceftriaxone. A total of 458 men and 447 women were enrolled. Of these, 312 men (68%) and 245 women (55%) were evaluable for efficacy. The treatment groups were demographically similar. Among evaluable men, fleroxacin eradicated 154 of 155 (99%; 95% confidence interval [CI]: 98.1-100%) urethral and 2 of 2 pharyngeal infections, while ceftriaxone eradicated 156 of 156 (95% CI: 99.4-100%) urethral and 5 of 5 pharyngeal infections. Among evaluable women, fleroxacin eradicated 127 of 128 (99%; 95% CI: 97.7-100%) cervical, 20 of 20 anorectal, 16 of 16 urethral, and 7 of 7 pharyngeal infections, while ceftriaxone eradicated 108 of 108 (95% CI: 99.1-100%) cervical, 24 of 24 anorectal, 25 of 25 urethral, and 9 of 9 pharyngeal infections. Adverse events were reported by 68 (16%) of 426 subjects in the fleroxacin group and 20 (5%) of 380 in the ceftriaxone group (p < 0.0001). The most common adverse events reported by the patients who received fleroxacin were nausea (5%), headache (3%), and vaginitis (3%). One patient had severe vomiting, 19 participants had adverse reactions classified as moderate, and 48 patients had mild adverse reactions. Fleroxacin was highly effective in the treatment of uncomplicated gonorrhea and represents an oral alternative to ceftriaxone. Adverse events were more common with fleroxacin than with ceftriaxone.

Administration, Oral↗
PubMed1993

Persistent sciatic artery: collective review and management.

One of the rarer anatomic variants is persistent sciatic artery. Only 93 cases have been reported since the first description of this anomaly. The earlier reports were mainly pathologic descriptions, whereas the more recent have been clinically oriented. There is a slight male predominance, and the average age of presentation is 49 years old (range 6 months to 85 years). The majority of patients have symptoms of a mass, ischemia, or gluteal pain. There is no preference for the right or left side, and one in four patients has both legs affected. In this anomaly the sciatic vessel acts as the principal blood supply to the lower limb. One half of all patients develop aneurysms that are characteristically located caudal to the sciatic notch as opposed to gluteal aneurysms that are cephalad to this landmark. Various methods (some now obsolete) have been tried to treat these aneurysms, but the best results were obtained through aneurysm ablation and vascular reconstruction. Arterial bypasses succeeded when used for ischemic complications of persistent sciatic artery. Optimal management of this condition requires prompt recognition, an understanding of the developmental anatomy, exclusion and bypass of aneurysms, appropriate vascular intervention for ischemic sequelae, and close observation of asymptomatic individuals.

Arteries↗
PubMed1993

An attempt to reproduce crystal-associated cholangitis in lambs in experimental dosing of sarsasapogenin or diosgenin alone and in combination with sporidesmin.

No liver damage occurred in a group of 21 lambs dosed intraruminally with up to 9 g of sarsasapogenin or diosgenin daily for 10 consecutive days. In contrast, seven out of 15 lambs dosed with 0.1 mg of sporidesmin/kg liveweight in combination with sarsasapogenin and three out of six lambs dosed with sporidesmin in combination with diosgenin developed liver lesions. These were typical of those induced by sporidesmin. One lamb dosed with sporidesmin in combination with 9 g of diosgenin developed a crystal-associated cholangitis typical of Panicurn intoxication and alveld. No sapogenins were detected in urine by gas chromatography-mass spectrometry. The results suggest that orally administered sarsasapogenin and diosgenin are either not hepatotoxic per se or are too poorly absorbed to elicit a toxic response. The results provide only weak evidence that sporidesmin may be involved in the aetiology of Panicurn intoxication.

Journal Article↗
PubMed1993

CHIP28 water channels are localized in constitutively water-permeable segments of the nephron.

The sites of water transport along the nephron are well characterized, but the molecular basis of renal water transport remains poorly understood. CHIP28 is a 28-kD integral protein which was proposed to mediate transmembrane water movement in red cells and kidney (Preston, G. M., T. P. Carroll, W. B. Guggino, and P. Agre. 1992. Science [Wash. DC]. 256:385-387). To determine whether CHIP28 could account for renal epithelial water transport, we used specific polyclonal antibodies to quantitate and localize CHIP28 at cellular and subcellular levels in rat kidney using light and electron microscopy. CHIP28 comprised 3.8% of isolated proximal tubule brush border protein. Except for the first few cells of the S1 segment, CHIP28 was immunolocalized throughout the convoluted and straight proximal tubules where it was observed in the microvilli of the apical brush border and in basolateral membranes. Very little CHIP28 was detected in endocytic vesicles or other intracellular structures in proximal tubules. Uninterrupted, heavy immunostaining of CHIP28 was also observed over both apical and basolateral membranes of descending thin limbs, including both short and long loops of Henle. These nephron sites have constitutively high osmotic water permeabilities. CHIP28 was not detected in ascending thin limbs, thick ascending limbs, or distal tubules, which are highly impermeable to water. Moreover, CHIP28 was not detected in collecting duct epithelia, where water permeability is regulated by antidiuretic hormone. These determinations of abundance and structural organization provide evidence that the CHIP28 water channel is the predominant pathway for constitutive transepithelial water transport in the proximal tubule and descending limb of Henle's loop.

Animals↗
PubMed1993

Prospective evaluation of immediate reconstruction after mastectomy.

OBJECTIVE: The authors prospectively studied the impact of immediate breast reconstruction on patients undergoing mastectomy. SUMMARY BACKGROUND DATA: Despite the advocation of a breast-conserving approach to the treatment of breast cancer, many women continue to medically require or choose mastectomy for the treatment of breast cancer. In recent years, immediate breast reconstruction has become an alternative to either mastectomy alone or to delayed reconstruction. METHODS: A prospective database of 216 patients who underwent mastectomy with immediate reconstruction was established. In this series, 94 procedures involved implants or tissue expanders, and 124 tissue transfers were performed. RESULTS: The overall complication rate was 15.3%; only 9% of patients who underwent autologous tissue transfers required secondary procedures. When implants were performed, the overall rate of prosthetic loss was 8%. The majority of patients (n = 101) underwent transverse rectus abdominis musculocutaneous (TRAM) flaps. Twenty-six of the 38 (17.5%) patients who required transfusion were from this group. Partial flap losses in this group (7%) were correlated to a history of heavy smoking. With a median follow-up of 33.2 months, only two patients had recurred locally. According to patient opinion, autologous tissue transfers resulted in a statistically better cosmetic result. CONCLUSIONS: Immediate reconstruction can be performed safely and with excellent cosmetic results.

Adult↗
PubMed1993

Aquaporin CHIP: the archetypal molecular water channel.

Despite longstanding interest by nephrologists and physiologists, the molecular identities of membrane water channels remained elusive until recognition of CHIP, a 28-kDa channel-forming integral membrane protein from human red blood cells originally referred to as "CHIP28." CHIP functions as an osmotically driven, water-selective pore; 1) expression of CHIP conferred Xenopus oocytes with markedly increased osmotic water permeability but did not allow transmembrane passage of ions or other small molecules; 2) reconstitution of highly purified CHIP into proteoliposomes permitted determination of the unit water permeability, i.e., 3.9 x 10(9) water molecules.channel subunit-1 x s-1. Although CHIP exists as a homotetramer in the native red blood cell membrane, site-directed mutagenesis studies suggested that each subunit contains an individually functional pore that may be reversibly occluded by mercurial inhibitors reacting with cysteine-189. CHIP is a major component of both apical and basolateral membranes of water-permeable segments of the nephron, where it facilitates transcellular water flow during reabsorption of glomerular filtrate. CHIP is also abundant in certain other absorptive or secretory epithelia, including choroid plexus, ciliary body of the eye, hepatobiliary ductules, gall bladder, and capillary endothelia. Distinct patterns of CHIP expression occur at these sites during fetal development and maturity. Similar proteins from other mammalian tissues and plants were later shown to transport water, and the group is now referred to as the "aquaporins." Recognition of CHIP has provided molecular insight into the biological phenomenon of osmotic water movement, and it is hoped that pharmacological modulation of CHIP function may provide novel treatments of renal failure and other clinical problems.

Amino Acid Sequence↗