The effects of acute phosphate supplementation in subjects of different aerobic fitness levels

Six trained cyclists (high-fitness group) and six untrained individuals (low-fitness group), performed a 20-min cycle ergometer exercise test at 70% of maximum oxygen consumption (VO2max) followed by a 30-min rest period and then an incremental ride to exhaustion on two occasions, 1 week apart. Ninety minutes prior to exercise subjects consumed a drink containing either 22.2 g dibasic calcium phosphate (DCP; treatment) or calcium carbonate (placebo). Blood was drawn prior to drink ingestion, during submaximal exercise, during recovery and at exhaustion for determination of blood 2,3-DPG, blood ATP, plasma lactate, plasma phosphate, haemoglobin and haematocrit. Throughout exercise, cardiorespiratory variables [oxygen uptake (VO2), minute ventilation, (VE), respiratory exchange ratio, heart rate and oxygen pulse] were monitored, and ratings of perceived exertion obtained. Although there was a trend for the low-fitness group to have a higher plasma phosphate concentration prior to treatment ingestion, no treatment effects on plasma phosphate were noted at any sample time in either group. 2,3-DPG, VO2, oxygen pulse, VE, time to exhaustion and VO2max were significantly higher in the high-fitness group; however, no differences in these variables were observed as a result of phosphate ingestion. Plasma lactate was significantly lower in the high-fitness group during the submaximal exercise and the recovery period, but again phosphate ingestion had no effect. These results suggest that acute DCP supplementation is not effective as an ergogenic aid and that aerobic fitness level does not affect the response to phosphate supplementation.

The role of scanning probe microscopy in drug delivery research

The success of a drug delivery system is often dependent on the surface properties of the device. These surface properties will determine the complex dynamic interfacial events that occur when the system is introduced into the aqueous environment of a patient. Development of the scanning probe microscopes has provided a number of very powerful new surface analytical techniques that are making a significant contribution to the characterization of drug delivery systems and the interfacial processes that occur when such systems are exposed to aqueous living environments. In this review, we describe the design and attributes of these instruments and discuss the impact of the techniques on a wide range of drug delivery research. The scanning probe microscopes are providing new insights into important problems concerning drug delivery, including the molecular structure of polymeric biomaterial surfaces, the conformation of target biomolecules, the influence of morphology on biodegradation, the adsorption of proteins to synthetic surfaces, and the structure and interactions of colloidal particles. As the whole field of scanning probe microscopy continues to advance, drug delivery research is set to benefit; in the final section of the review, the future potential derived from the ability to characterize new surface properties under aqueous conditions is discussed.

Mutations affecting the biosynthesis of S-adenosylmethionine cause reduction of DNA methylation in Neurospora crassa

A temperature-sensitive methionine auxotroph of Neurospora crassa was found in a collection of conditional mutants and shown to be deficient in DNA methylation when grown under semipermissive conditions. The defective gene was identified as met-3, which encodes cystathionine-gamma-synthase. We explored the possibility that the methylation defect results from deficiency of S-adenosylmethionine (SAM), the presumptive methyl group donor. Methionine starvation of mutants from each of nine complementation groups in the methionine (met) pathway (met-1, met-2, met-3, met-5, met-6, met-8, met-9, met-10 and for) resulted in decreased DNA methylation while amino acid starvation, per se, did not. In most of the strains, including wild-type, intracellular SAM peaked during rapid growth (12-18 h after inoculation), whereas DNA methylation continued to increase. In met mutants starved for methionine, SAM levels were most reduced (3-11-fold) during rapid growth while the greatest reduction in DNA methylation levels occurred later. Addition of 3 mM methionine to cultures of met or cysteine-requiring (cys) mutants resulted in 5-28-fold increases in SAM, compared with wild-type, at a time when DNA methylation was reduced approximately 40%, suggesting that the decreased methylation during rapid growth in Neurospora is not due to limiting SAM. DNA methylation continued to increase in a cys-3 mutant that had stopped growing due to methionine starvation, suggesting that methylation is not obligatorily coupled to DNA replication in Neurospora.

In vivo inhibition of oestrone sulphatase and dehydroepiandrosterone sulphatase by oestrone-3-O-sulphamate

Many tumours in endocrine-sensitive tissues, such as the breast and endometrium, are hormone-dependent and the hydrolysis of oestrone sulphate (EIS) to oestrone by oestrone sulphatase (EI-STS) is a major source of oestrogen in such tumours. Oestrone-3-O-sulphamate (EMATE) has been shown to be a potent EI-STS inhibitor in vitro, and in this study its ability to inhibit enzyme activity in vivo was examined. EMATE was initially administered to female rats for 7 days, after which liver EI-STS activity was measured. As EMATE also inhibits a related sulphatase in vitro, dehydroepiandrosterone sulphatase (DHA-STS), its effect on the activity of this enzyme in vivo was also investigated. DHA-STS has a pivotal role in regulating the synthesis of another steroid with potent oestrogenic properties, androstenediol. Administration of EMATE almost completely inhibited liver EI-STS (99%) and DHA-STS (99%) activities and was active when given by the oral or subcutaneous routes. After a single dose of EMATE or following the cessation of multiple doses for 10 days, liver EI-STS activity remained inhibited ( > 95%) for up to 7 and 10 days, respectively. Other compounds, such as 4-hydroxytamoxifen and the "pure" antioestrogen ICI 182,780, which are reported to inhibit EI-STS activity in vitro, did not inhibit activity in vivo. In a preliminary study, EMATE, when injected over a 12-day period, effectively reduced the growth of EIS-stimulated nitrosomethyl-urea-induced mammary tumours in ovariectomised rats and inhibited tumour sulphatase activity in treated animals.

Improving the primary management of emergency surgical admissions: a controlled trial

The initial screening by senior surgical staff of surgical patients referred for emergency hospital admission should result in improved patient management. The present study was undertaken to determine the effects of this policy. The primary outcome measure was hospital admission rates. The number of operations, diagnostic investigations, initial treatments, deaths, length of stay and bed days per 100 referrals were also measured. The results suggest a 20 per cent reduction in emergency surgical admissions, an important potential benefit to the health service, and to individual patients.

Scanning tunnelling microscopy studies of beta-amyloid fibril structure and assembly

Alzheimer's disease is in part characterised by the deposit of beta-amyloid peptide in the form of fibrils in the brain. In this study, the scanning tunnelling microscope (STM) has been used to provide high resolution images of synthetic fibril structure and formation as a function of time. Short fibrils are observed following brief peptide incubation times. At longer incubation periods ribbon like filaments were observed. These results suggest that beta-amyloid self-assembly is an ordered process, with a correlation between time of incubation and length of beta-amyloid filament growth.

The antiemetic effectiveness of droperidol during morphine patient-controlled analgesia

This prospective, double-blind study examined the antiemetic effectiveness of the addition of droperidol to a morphine solution for use in patient-controlled analgesia in a group of 50 patients undergoing elective lumbar laminectomy. The addition of 20 mg droperidol to 120 mg morphine in 60 ml saline given by a Baxter 'Infusor' patient-controlled analgesia device reduced the incidence of vomiting as compared to the addition of sodium chloride from 42.8% to 12.5% (p = 0.028) and of nausea from 71.4% to 29.2% (p = 0.005). The proportion of patients requiring rescue antiemetic therapy was reduced from 47.6% to 16.7% (p = 0.025) and the time interval to the first use of rescue antiemetic agent was significantly prolonged (p = 0.029). The use of droperidol was associated with an increased degree of sedation during the first 12 h after operation.

The role of cytokines and sulphatase inhibitors in regulating oestrogen synthesis in breast tumours

Synthesis of oestrogens within breast tissues makes an important contribution to the high concentrations of oestradiol which are found in breast tumours. The activities of the enzymes involved in oestrogen synthesis, i.e. the aromatase, oestradiol dehydrogenase (E2DH) and oestrone sulphatase (E1-STS), can be stimulated by several growth factors and cytokines. As it is possible that some of these factors may be derived from cells of the immune system (macrophages and lymphocytes), the effects of basic fibroblast growth factor (bFGF) and interleukin-2 (IL-2), which are produced by these cells, on E2DH activity was examined in MCF-7 cells. Treatment of these cells with bFGF resulted in a dose-dependent increase in E2DH reductive activity whereas IL-2 was inactive at the concentration tested. To obtain further evidence that factors produced by macrophages and lymphocytes can modulate the activities of enzymes involved in oestrogen synthesis, conditioned medium was collected from these cells and found to stimulate both E1-STS and E2DH activities. In addition to understanding the control of oestrogen synthesis in breast tumours an inhibitor to block the synthesis of oestrone via the oestrone sulphatase pathway was developed. Oestrone-3-O-sulphamate (EMATE) is a potent, irreversible, inhibitor of E1-STS. A single dose of EMATE (10 mg/kg) inhibited tissue E1-STS activity in rats by more than 95% for up to 7 days, indicating that this compound may have considerable therapeutic potential for the treatment of breast cancer. Evidence is also reviewed that another steroid sulphatase, dehydroepiandrosterone sulphate sulphatase, may have a crucial role in regulating cytokine production and that this may indirectly control tumour oestrogen synthesis.

Carpal malalignment following intra-articular fractures of the distal radius in a working population

In a review of 52 consecutive intra-articular fractures of the wrist (mean age 41 years), 18 developed one of five carpal malalignment patterns. Seven patients developed a volar intercalated collapse pattern. Although showing some loss of motion and/or grip strength, this group remains relatively pain free on follow-up. Patients who developed dorsal translation (six cases) or a dorsal intercalated collapse pattern (one case) were the most symptomatic, with loss of grip strength, decreased range of motion and pain being prevalent.

Development of an ELISA using a universal method of enzyme-labelling drug-specific antibodies. Part I: Detection of dexamethasone in equine urine

The development, validation, and application of an ELISA for dexamethasone in equine urine is described. The drug-protein conjugate was immobilised in microtitre plate wells and antiserum raised against the same drug-protein conjugate was allowed to compete with sample or standard drug and the immobilised drug-protein conjugate. The proportion of antiserum binding to the immobilised drug-protein conjugate was detected using a biotinylated protein G/extravidin-alkaline phosphatase complex in situ and measurement of the substrate product. The method was used to detect the presence of drug-derived material in unextracted diluted urine after the administration of a single i.m. dose of dexamethasone at approximately 0.04 mg/kg to a thoroughbred horse. Validation of the method was carried out against a radioimmunoassay and GC/MS analysis.

Characteristics of plasma protein binding of tacrine hydrochloride: a new drug for Alzheimer's disease

The aim of this study was to characterise the plasma protein binding of tacrine hydrochloride (THA) in vitro. Binding was assessed in the plasma of 11 healthy individuals aged 20 to 27 years using ultrafiltration followed by HPLC assay. At THA concentrations from 10 to 100 ng/ml protein binding ranged from 78.6 to 71.0%. Binding to commercially available human albumin ranged from 41.7 to 38.3% and to human alpha 1-acid glycoprotein from 23.1 to 12.4% over the THA concentrations from 25 to 100 ng/ml. THA binding and total plasma protein, plasma albumin and alpha 1-acid glycoprotein were measured in healthy young subjects (n = 13), healthy elderly individuals (n = 12) and patients hospitalised with acute illnesses (n = 8). There were significant differences between the groups in total plasma protein, plasma albumin and in alpha 1-acid glycoprotein but no differences in the protein binding of THA which remained constant at about 75%. There was no correlation between THA binding and any plasma protein concentration. The THA binding was not high enough to be of major significance clinically or to reduce the validity of total plasma THA measurement in therapeutic monitoring.

Compliance with guidelines for choice of radiographic projections: a multicentre study

A study of compliance with guidelines for choice of radiographic projections was carried out in each of six centres. The study concerned 5851 examinations undertaken by 116 radiographers under the supervision of 29 consultant radiologists. The results showed good compliance between centres for examination of the chest (range 81-93%), abdomen (range 73-100%), thoracic spine (range 82-96%), pelvis/hip (range 78-99%) but not for examination of cervical spine (range 0-85%), paranasal sinus (range 0-100%) and lumbar spine (range 52-84%). The reasons given for these wide variations are discussed and estimates are given for the potential reductions in exposure to the UK population consequent upon national implementation of guidelines such as these.

Atomic force microscopy and scanning tunnelling microscopy: refining techniques for studying biomolecules

The scanning tunnelling microscope and the atomic force microscope offer the prospect of real-time, nanometre-scale imaging of biomolecules and biosurfaces under physiological environments. Much effort is therefore being made to establish these techniques as routine biophysical tools. The considerable recent progress that has been made in biotechnological applications is reviewed, highlighting specific examples of the applications of this new and exciting method of analysis.

A scanning tunnelling microscopy comparison of passive antibody adsorption and biotinylated antibody linkage to streptavidin on microtiter wells

An antiferritin antibody was either, (a) passively adsorbed to microwells or (b) biotinylated and immobilised to streptavidin coated microwells. Scanning tunnelling microscope (STM) imaging of these well surfaces coated with a platinum (95%) carbon (5%) coating (Pt/C) conductive layer showed a randomly oriented array of antibodies for passive adsorption whereas for biotin-streptavidin immobilisation there was a more uniform and even distribution of antibodies on the well surface. On further incubation with ferritin STM imaging showed that for passive adsorption approximately 5% of the surface was functional, while for the biotinylated antibody it was greater than 60%. The images presented in this paper show graphically the loss of functionality that occurs using passive adsorption and, conversely, the preservation of antibody functionality using the biotin-streptavidin linkage for antibody immobilisation. These results correlate well with the work of others in the field.

Stem cell responses in myelosuppressed mice following sequential treatment with recombinant human interleukin 1 (rHuIL-1), recombinant murine interleukin 3 (rMuIL-3) and recombinant human macrophage colony-stimulating factor (rHuM-CSF)

In vivo, recombinant human interleukin 1 alpha (rHuIL-1 alpha) + recombinant human macrophage colony-stimulating factor (rHuM-CSF) (IL-1 + M-CSF) effectively serves as a rescue agent for myelosuppression by enhancing the recovery of hematopoietic stem cell (HSC) subpopulations following treatment with 5-fluorouracil (5-FU). Because in vitro studies have suggested that hematopoietic recovery in 5-FU-treated bone marrow (FUBM) may proceed from a 5-FU resistant, (IL-1 + IL-3 + M-CSF-responsive) high proliferative potential HSC subpopulation of colony forming cells (HPP-CFC), studies were carried out to determine whether the addition of recombinant murine interleukin 3 (rMuIL-3) (IL-3) to either IL-1 or IL-1 + M-CSF would further enhance the recovery of HSC subpopulations in myelosuppressed C57Bl/6 mice. With the exception of the HPP-CFC, IL-3 dampened, rather than enhanced, the accelerated recovery of 8 d and 12 d colony forming units-spleen (8 d and 12 d CFU-S) and the committed macrophage progenitor (CFU-M) associated with in vivo treatment with IL-1 alone. Similarly, IL-3 interfered with the enhanced recovery of those HSC subpopulations in FUBM influenced by the synergistic interaction of IL-1 + M-CSF. This interference, however, was observed only when the rMuIL-3 was administered on day 2 or 3 of a four-day treatment with IL-1 + M-CSF. There was, however, no evidence that IL-3 exerted a negative influence on the restoration of granulocytes in the myelosuppressed animals. Moreover, sequencing studies provided data suggesting that the dampening effects of IL-3 on the synergistic interaction of IL-1 + M-CSF resulted from both an enhanced differentiation of the more primitive HSC subpopulations and a significant, but preferential, mobilization of the more mature 8 d CFU-S and CFU-M to extramedullary organs and that the mobilization of these more mature HSC subpopulations was temporally linked to their generation from the recovering HPP-CFC and 12 d CFU-S subpopulations.

Abnormal chromosome behavior in Neurospora mutants defective in DNA methylation

The function and regulation of DNA methylation in eukaryotes remain unclear. Genes affecting methylation were identified in the fungus Neurospora crassa. A mutation in one gene, dim-2, resulted in the loss of all detectable DNA methylation. Abnormal segregation of the methylation defects in crosses led to the discovery that the methylation mutants frequently generate strains with extra chromosomes or chromosomal parts. Starvation for S-adenosylmethionine, the presumed methyl group donor for DNA methylation, also produced aneuploidy. These results suggest that DNA methylation plays a role in the normal control of chromosome behavior.

Effect of intraoperative inspired gas mixtures on postoperative nocturnal oxygen saturation

Continuous postoperative nocturnal pulse oximetry was performed in 20 patients undergoing elective cholecystectomy to examine if the composition of anaesthetic gas mixtures affects postoperative gas exchange. The patients were allocated randomly to receive either nitrogen or nitrous oxide during anaesthesia, and oximetry was performed on the night before operation and the first and third nights after operation. Considerable oxygen desaturation was seen in both groups. During the first night after operation the proportion of the night during which oxygen saturation was less than 85% was greater in the nitrogen group than in the nitrous oxide group, but there was no significant difference between the mean overnight saturation values of the two groups.

Membrane protein retention in the yeast Golgi apparatus: dipeptidyl aminopeptidase A is retained by a cytoplasmic signal containing aromatic residues

The mechanism by which yeast dipeptidyl aminopeptidase (DPAP) A, type II integral membrane protein, is retained in the late Golgi apparatus has been investigated. Prior work demonstrated that the 118-amino acid cytoplasmic domain is both necessary and sufficient for Golgi retention and that mutant or overexpressed DPAP A no longer retained in the Golgi was delivered directly to the vacuolar membrane (Roberts, C. J., S. F. Nothwehr, and T. H. Stevens. 1992. J. Cell Biol. 119:69-83). Replacement of the DPAP A transmembrane domain with a synthetic hydrophobic sequence did not affect either Golgi retention of DPAP A or vacuolar delivery of the retention-defective form of DPAP A. These results indicate that the DPAP A transmembrane domain is not involved in either Golgi retention or targeting of this membrane protein. A detailed mutational analysis of the cytoplasmic domain of DPAP A indicated that the most important elements for retention were within the eight residue stretch 85-92. A 10-amino acid region from DPAP A (81-90) was sufficient for Golgi retention of alkaline phosphatase, a type II vacuolar membrane protein. Detailed mutational analysis within this 10-amino acid sufficient region demonstrated that a Phe-X-Phe-X-Asp motif was absolutely required for efficient retention. The efficiency of Golgi retention via the DPAP A signal could be diminished by overexpression of wild type but not retention-defective versions of Kex2p, another late Golgi membrane protein, suggesting that multiple Golgi membrane proteins may be retained by a common machinery. These results imply a role for a cytoplasmic signal involving aromatic residues in retention of late Golgi membrane proteins in the yeast Saccharomyces cerevisiae.

Serum concentrations of tacrine hydrochloride predict its adverse effects in Alzheimer's disease

OBJECTIVE

To assess the value of serum measurements of tacrine hydrochloride and its metabolite in predicting risk of adverse reaction in Alzheimer's disease.

METHODS

The study was an outpatient-based controlled clinical trial. Study subjects were 35 female and 31 male patients who were receiving 50 to 150 mg tacrine hydrochloride per day.

RESULTS

Serum concentration of tacrine hydrochloride and ratio of tacrine hydrochloride to metabolite were significantly higher in the 45 patients with symptomatic adverse effects (p < 0.001). The tacrine hydrochloride to metabolite ratio was significantly higher (p < 0.05) in the 30 patients in whom abnormal liver function developed, but concentration of tacrine hydrochloride was not significantly higher. Women showed a higher incidence of adverse effects (p < 0.05), and tacrine hydrochloride concentrations were higher (p < 0.05). Tacrine hydrochloride concentration and tacrine hydrochloride to metabolite ratio were higher in both men and women in whom adverse effects developed.

CONCLUSION

Tacrine hydrochloride concentration is valuable in predicting the development of adverse effects, and its measurement may improve the use of the drug.

International nursing: a student outlook

World health depends upon our field of vision. If we selectively view the world from a narrow perspective, we will be unable to function effectively as nurses. The sobering reality of health conditions throughout the world should awaken our consciousness and sharpen our focus on priorities for the future. We can agree with Lindquist, that "nursing must be viewed from a global perspective if it is to influence the quality of health care provided in the future." Although not every student has the means and availability to travel overseas in a volunteer capacity, students may begin to examine the possibilities and start their own correspondence with an international agency. Regardless of our realm of service, the opportunity to provide care for individuals of all cultures, whether abroad or at home, remains the highest privilege of our profession.

Membrane protein sorting in the yeast secretory pathway: evidence that the vacuole may be the default compartment

The targeting signals of two yeast integral membrane dipeptidyl aminopeptidases (DPAPs), DPAP B and DPAP A, which reside in the vacuole and the Golgi apparatus, respectively, were analyzed. No single domain of DPAP B is required for delivery to the vacuolar membrane, because removal or replacement of either the cytoplasmic, transmembrane, or lumenal domain did not affect the protein's transport to the vacuole. DPAP A was localized by indirect immunofluorescence to non-vacuolar, punctate structures characteristic of the yeast Golgi apparatus. The 118-amino acid cytoplasmic domain of DPAP A is sufficient for retention of the protein in these structures, since replacement of the cytoplasmic domain of DPAP B with that of DPAP A resulted in an immunolocalization pattern indistinguishable from that of wild type DPAP A. Overproduction of DPAP A resulted in its mislocalization to the vacuole, because cells expressing high levels of DPAP A exhibited vacuolar as well as Golgi staining. Deletion of 22 residues of the DPAP A cytoplasmic domain resulted in mislocalization of the mutant protein to the vacuole. Thus, the cytoplasmic domain of DPAP A is both necessary and sufficient for Golgi retention, and removal of the retention signal, or saturation of the retention apparatus by overproducing DPAP A, resulted in transport to the vacuole. Like wild type DPAP B, the delivery of mutant membrane proteins to the vacuole was unaffected in the secretory vesicle-blocked sec1 mutant; thus, transport to the vacuole was not via the plasma membrane followed by endocytosis. These data are consistent with a model in which membrane proteins are delivered to the vacuole along a default pathway.