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Biomedical subjects

A Brain

Publications and source records attributed to A Brain.

18 recordsLinked to original sources
PubMed2000

A study of drug-carrier interactions in dry powder inhaler formulations using the Andersen cascade impactor, X-ray microanalysis and time of flight aerosol beam spectrometry (TOFABS).

The purpose of this study was to determine the in vitro deposition of both drug (albuterol sulfate) and carrier (lactose) particles in relation to each other from a dry powder inhaler formulation using an Andersen cascade impactor (ACI) and time of flight aerosol beam spectrometry (TOFABS). In addition, scanning electron microscopy (SEM) combined with X-ray microanalysis was employed to distinguish albuterol sulfate from lactose. Drug particles apparently penetrated deeper into the impactor than lactose particles contained in the formulation. In some certain stages of impactor, drug particles were separated from lactose particles. Although the TOFABS cannot distinguish between albuterol sulfate and lactose, the TOF spectra obtained from the Aerosizer would appear to be partly indicative of the interactions which exist between drug and carrier. One symmetrical TOF peak was obtained from drug or lactose alone. The TOF peak of the drug was always lower than the TOF of lactose. The times obtained for each powder between experiments were highly reproducible and typical of material and particle size. The use of SEM-X-ray microanalysis also allowed some qualitative characterization of shape and state of association of the two components.

Aerosols↗
PubMed1998

Relationship between serum alkaline phosphatase and pyridoxal-5'-phosphate levels in hypophosphatasia.

1. Hypophosphatasia is a disorder characterized by low serum levels of alkaline phosphatase (ALP) and a range of skeletal deformities. The levels of a number of phosphorylated metabolites, namely phosphoethanolamine and pyrophosphate, are characteristically raised. Levels of pyridoxal-5'-phosphate (PLP) have also been reported to be raised. 2. Hypophosphatasia is a rare disease and experience of measuring PLP in patients is lacking. We have had the chance to look at PLP levels in four families with hypophosphatasia, specifically to examine the quantitative relationship between ALP and PLP which has not been described before. 3. We confirmed that PLP levels are raised in hypophosphatasia and related to the disease severity. A significant negative linear relationship was found between the log PLP and log ALP (log PLP = 5.99-2.76 log ALP; r = -0.85, P < 0.001). 4. Measurement of PLP is simpler than some of the phosphorylated compounds, e.g. pyrophosphate. PLP may be a useful measure in patients with a suspected diagnosis of hypophosphatasia or for screening family members to detect potential heterozygotes and to monitor any response to therapy. 5. There did not appear to be any adverse clinical effects in relation to disturbed vitamin B6 metabolism in hypophosphatasia. 6. Vitamin B6 is used therapeutically in a number of conditions with monitoring of PLP levels. In these conditions PLP levels should be interpreted in conjunction with the prevailing serum ALP levels as the metabolism of these compounds is closely inter-related.

Adult↗
PubMed1996

Optimal shape of the laryngeal mask cuff: the influence of three deflation techniques.

A randomised, single-blinded, controlled trial was conducted to determine if a new laryngeal mask deflation tool offered any advantages over manual or free deflation. Ten laryngeal mask airways were tested and the deflation tool provided a significantly superior and more consistent shape than either hand manipulation or the free deflation, but did not offer any benefits in terms of residual volume. The deflator tool should encourage wider use of the standard recommended insertion technique. It can be used as a backup when manual deflation cannot provide the correct shape and may be useful for researchers studying laryngeal mask airway placement.

Anesthesiology↗
PubMed1993

Reduced renal hemodynamic response to atrial natriuretic peptide in elderly volunteers.

Aging is associated with decreased ability to excrete salt and water, thus increasing the susceptibility to volume overload in older individuals. Meanwhile, plasma levels of atrial natriuretic peptide (ANP) increase progressively with age for unknown reasons. We compared the natriuretic and renal hemodynamic responses to low-dose ANP infusion in an elderly group of volunteers (mean age, 74 years) with those of a group of younger subjects (mean age, 29 years). A significant reduction below baseline values in effective renal plasma flow occurred in the young group after the 2-hour peptide infusion (657 +/- 125 v 476 +/- 92 mL/min [mean +/- 1 SD]) when compared with the elderly group (two-way analysis of variance; P < 0.02). A concomitant increase in renal vascular resistance was noted in the young group only during the same period (6,631 +/- 1,384 v 9,136 +/- 2,126 dyn s cm2 x 10(6)). This increase was also significantly higher than that in the elderly group (analysis of variance; P < 0.02). Both groups demonstrated similar natriuretic responses. Absolute sodium excretion had increased significantly above baseline values in both young and elderly subjects at the end of the 2-hour peptide infusion (111 +/- 25 mumol/min to 183 +/- 33 mumol/min v 107 +/- 23 mumol/min to 198 +/- 56 mumol/min) and remained elevated until 1 hour postinfusion. We conclude that the elderly subjects in our study demonstrated a diminished renal hemodynamic response to infusion of ANP while preserving a natriuretic response similar to that found in the younger subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The frusemide test: simple screening test for renal acidification defect in urolithiasis.

Urinary pH was first labelled as a risk factor for patients with recurrent calcium stone disease of the renal tract in 1978. The standard diagnostic test for patients with a history of stones, who appear to have urinary acidification defects is the ammonium chloride test. However, the performance of this test results in significant morbidity, particularly nausea and vomiting, and as a result there is little enthusiasm for screening for such defects. We describe a screening test that may be used to determine which patients require more definitive testing. It involves an oral dose of frusemide (40 mg) followed by half-hourly urine sampling for pH. For the detection of a renal tubular acidification defect, the frusemide test had sensitivity = 100%, specificity = 82%, predictive value of a positive result = 40%, predictive value of a negative result = 100%, screening efficiency = 84%, and there was no morbidity. During the ammonium chloride test 80% of the patients vomited or felt very nauseated.

Ammonium Chloride↗
PubMed1992

The interaction of Streptococcus pneumoniae with intact human respiratory mucosa in vitro.

The interaction of Streptococcus pneumoniae with human ciliated upper respiratory mucosa was studied in an agar-embedded organ culture of nasal turbinate tissue, which only exposed the intact epithelial surface and its secretion. The ciliary beat frequency, measured along the edge of the organ culture, was slowed by 13% in the presence of S. pneumoniae after 16 h (p less than 0.05) compared with the control, and by 24% after 24 h (p less than 0.01). Light microscopy showed bacteria in a thickened gelatinous layer, which obscured the surface of the organ culture. Transmission and scanning electron microscopy confirmed the association of bacteria with the gelatinous layer above an epithelial surface which showed only minor changes compared to uninfected control organ cultures. Contact between bacteria and normal or damaged epithelial cells was not seen. S. pneumoniae in organ culture developed projections from their surface, which were not present after broth culture. S. pneumoniae interactions with epithelial-derived secretions, the formation of a thickened gelatinous layer, and the effects of bacterial toxins on ciliary motility, may be important during colonization of the respiratory tract.

Cilia↗
PubMed1990

Spreading of wheat germ agglutinin-induced erythrocyte contact by formation of spatially discrete contacts.

The time dependence of agglutination and cell-cell contact spreading in human erythrocytes exposed to wheat germ agglutinin (WGA) was characterized by light and electron microscopy. Cells (3 x 10(7)/mL) had a threshold lectin concentration in the range of 0.6-2.0 micrograms/mL for initial cell contact. Spreading was essentially completed within 60 and 2 min in undisturbed and gently agitated suspensions, respectively. The cells in large WGA agglutinates retained features of their initial disk form in contrast to the convex outlines of polycation or polyethylene glycol-induced agglutinates. Spreading of contact area was accompanied by development of a pattern of discrete contact regions separated by a distance of the order of 1 micron. Freeze fracture electron microscopy and studies with ferritin-labeled WGA showed no significant aggregation of intramembrane particles or specific lectin receptors under conditions when contact spreading occurred. It is argued that flow stress effects on cells in suspended agglutinates give rise to a situation where opposite membranes, at the leading edge of cell contact, are separated by a thin aqueous layer. When this intercellular water layer exceeds a critical length, it becomes unstable. The layer breaks up by surface wave development to form an array of intracellular water spaces. Formation of the aqueous spaces causes opposite membrane regions to move synchronously toward each other. Lectin molecules crosslink the wave crests to give spatially periodic contact points.

Cell Communication↗
PubMed1989

Survival of cultured allogeneic keratinocytes transplanted to deep dermal bed assessed with probe specific for Y chromosome.

To determine the survival of cultured allogeneic keratinocytes transplanted to a deep dermal bed 24 tattoos that had been removed by deep shave excision in 19 patients were grafted with sheets of cultured allogeneic keratinocytes from donors of the opposite sex. Cells carrying the Y chromosome were identified in biopsy specimens taken from the graft site by in situ DNA hybridisation with a biotinylated Y probe (pHY 2.1) and visualised with a technique using immunoperoxidase. The cultured allograft sites were biopsied one, two, and three weeks after transplantation. No male cells were identified in any biopsy specimen from female patients who were given transplants of male cultured keratinocytes, and all biopsy specimens from male patients, who received female cultured keratinocytes, showed percentages of male cells within the normal range for male skin. The beneficial effects of cultivated allogeneic keratinocytes result from effects on wound healing other than forming a successful graft that "takes."

Bandages↗
PubMed1987

Loop mattress suture.

Explore the source record for details and available documents.

Dermatologic Surgical Procedures↗
PubMed1987

Freeze-fracture electron microscopic observations on the effects of sulphydryl group reagents on human erythrocyte membranes.

Freeze-fracture electron microscopy of human red blood cells at pH 7.4 and 5.5 reveals the presence of membrane elevations (50-100 nm diameter). These are also observed after incubation of the erythrocytes with N-ethylmaleimide but not after incubation with p-chloromercuribenzene sulphonate. Neither of the sulphydryl-group reagents affects the distribution or size of intramembrane particles. The findings are discussed in the light of the effects of mercurials on erythrocyte membrane proteins.

Erythrocyte Membrane↗
PubMed1986

Water permeability in human erythrocytes: identification of membrane proteins involved in water transport.

The water permeability of human erythrocytes has been monitored by nuclear magnetic resonance (NMR) before and after treatment of the cells with various sulfhydryl reagents. Preincubation of the cells with N-ethylmaleimide (NEM), a non-inhibitory sulfhydryl reagent, results in a faster and more sensitive inhibition of water exchange by mercurials. The inhibition of water exchange by p-chloromercuribenzene sulfonate (PCMBS) was maximal at a binding of approximately 10 nmol PCMBS per mg protein when non-specific sulfhydryl groups are blocked by NEM. Inhibition by PCMBS has been correlated with the binding of 203Hg to erythrocyte membrane proteins. A significant binding of label to band 3 and the polypeptides in band 4.5 occurs, with approximately 1 mol of mercurial bound per mol of protein. Inhibition of water transport by sulfhydryl reagents does not induce major morphological changes in the cells as assessed by freeze-fracture and scanning electron microscopy.

4-Chloromercuribenzenesulfonate↗