The determination of lysergide (LSD) in urine by high-performance liquid chromatography-isotope dilution mass spectrometry (IDMS)

The use of isotope dilution mass spectrometry (IDMS) has been investigated for the forensic confirmation of lysergic acid diethylamide (LSD) in urine by LC-MS. The advantages of using a deuterated analog of LSD as an internal standard over methysergide are discussed. This study includes a comparison of the electrospray mass spectra of LSD, LSD-d3 and methysergide, and discusses the choice of suitable ions for use in selected ion monitoring (SIM) mode. An IDMS method is presented for the LC-MS confirmation of LSD in urine, with a limit of quantification (LOQ) of 0.5 ng/mL, reflecting the forensic requirement at this laboratory. Under some circumstances the LOQ can be improved to 0.1 ng/mL. This method is linear in the range tested (up to 10 ng/mL LSD in urine) and has been validated in terms of accuracy and precision.

Detailed active site configuration of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 at 1.9 A resolution

The three-dimensional structure of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 has been obtained in the presence of substrate using data recorded at a synchrotron. The structure of this approximately 140 kDa heterotetramer, refined at 1. 9 A resolution, reveals the detailed configuration of its redox cofactor, pyrroloquinoline quinone (PQQ). C4, one of the oxygen-bearing atoms of this orthoquinone is in a planar configuration while C5, which bears the other quinone oxygen, is tetrahedral, suggesting that the PQQ is in the semiquinone redox state. The substrate binding site has been identified close to PQQ and to the side chain of Asp297, the putative active site base. The proximity of the hydroxyl of methanol to C5 of PQQ compared to the greater separation of the substrate methyl group from C5 supports the addition-elimination reaction mechanism involving a hemiketal intermediate.

Diagnosing anaemia in pregnancy in rural clinics: assessing the potential of the Haemoglobin Colour Scale

Anaemia in pregnancy is a common and severe problem in many developing countries. Because of lack of resources and staff motivation, screening for anaemia is often solely by clinical examination of the conjunctiva or is not carried out at all. A new colour scale for the estimation of haemoglobin concentration has been developed by WHO. The present study compares the results obtained using the new colour scale on 729 women visiting rural antenatal clinics in Malawi with those obtained by HemoCue haemoglobinometer and electronic Coulter Counter and with the assessment of anaemia by clinical examination of the conjunctiva. Sensitivity using the colour scale was consistently better than for conjunctival inspection alone and interobserver agreement and agreement with Coulter Counter measurements was good. The Haemoglobin Colour Scale is simple to use, well accepted, cheap and gives immediate results. It shows considerable potential for use in screening for anaemia in antenatal clinics in settings where resources are limited.

Pancreatic islet autotransplantation combined with total pancreatectomy for the treatment of chronic pancreatitis--the Leicester experience

Islet autotransplantation offers the potential for preventing the surgically induced diabetes that is an inevitable consequence of total pancreatectomy. This paper describes the first islet autotransplant programme in the United Kingdom and the first series in the world to use the spleen as a site for the islet graft. Over an 11 month period, 7 patients underwent total pancreatectomy for chronic pancreatitis combined with a simultaneous islet autotransplant. All 7 patients had normal glucose-tolerance levels and normal C-peptide levels pre-operatively. In 6 patients, islets were embolized into the liver via the portal vein (median transplanted volume=8.5 ml). In addition, 3 patients received islets into the splenic sinusoids via a short gastric vein (median transplanted volume=4 ml). One patient received islets into the spleen alone. One patient died of a stroke 4 weeks post transplantation. Two patients have achieved insulin independence, with a further two patients achieving "transient" insulin independence (<1 month). The remaining 2 patients, although requiring reduced insulin doses, have not achieved insulin-independence. However, all patients have C-peptide levels within the normal range. In trying to explain these findings, split proinsulin levels were measured and found to be elevated. High levels of split proinsulin cross react with the C-peptide assay and this would explain the falsely elevated C-peptide levels. Indeed insulin levels in these patients were all below the normal range. These findings would suggest that the use of C-peptide levels as the "gold standard" for monitoring islet autograft function, may require reappraisal.

An investigation into the distribution of different collagen types within adult and juvenile porcine pancreata

One of the difficulties of porcine islet isolation is their fragility during collagenase digestion. The object of this study was to determine the distribution of 4 different collagen types within adult and juvenile porcine pancreata. Five different areas from each pancreas were analysed by light microscopy. The distribution of collagen types I, IV, V and VI were measured within the interlobar, intralobular (acinar), peri-insular and intra-islet regions. Their was an abundance of collagen type VI compared to I, IV and V in both the interlobar and intralobular septa in both juveniles (P<0.001) and adults (P<0.001). The periinsular collagen content also showed diversity. This was mainly attributable to the distribution of collagen type I (weak) and type VI (intense) in both adults and juveniles. In general, the peri-insular capsule was fragmentary and contained less than 50% of the total islet circumference. The latter finding taken together with the distributions of different collagen types can partly explain some of the variability of porcine islet isolation.

The relationship between asymptomatic human immunodeficiency virus infection and the prevalence and severity of anemia in pregnant Malawian women

The relationship between asymptomatic human immunodeficiency virus (HIV) infection and blood hemoglobin (Hb) concentration was examined in anemic pregnant women from a population with high prevalence of both anemia (60%) and HIV seropositivity (30%). Sera from 155 pregnant women with Hb levels < 10.5 g/dL were tested for HIV status, C-reactive protein (CRP), vitamin B12, retinol, and folate levels. The observed prevalence of HIV seropositivity in the group of women with anemia was 47.1% (95% confidence interval=39.2-55.0%). This is significantly higher than the HIV prevalence in the whole population (30.1%; P < 0.001). Median Hb values in HIV-seropositive and -seronegative women with anemia were 8.40 g/dL and 8.95 g/dL, respectively. Serum retinol, vitamin B12, and folate levels were not significantly different in the HIV-seropositive and -seronegative groups. In women who were HIV-seropositive with normal levels of CRP, a median decrease in Hb of 0.4 g/dL was observed. For those with serum CRP levels > 25 mg/l, the median decrease in Hb was 0.7 g/dL. Results indicate that asymptomatic HIV infection is associated with increased prevalence and severity of anemia in pregnancy in this population.

Iron status in pregnant women: which measurements are valid?

Anaemia in pregnancy in developing countries continues to be a public health problem of significant proportion. At least 50% of the anaemia has been blamed on iron deficiency. In populations where chronic inflammation and iron deficiency anaemia coexist, the criteria to accurately define iron status are not always clear. Similarly, in pregnancy, with marked physiological changes, cut-off points for biochemical parameters need to be re-examined. In this study we examined the diagnostic accuracy of iron parameters including mean cellular volume (MCV), serum iron, transferrin, total iron binding capacity (TIBC) and its saturation, zinc protoporphyrin (ZPP), ferritin and serum transferrin receptor (TfR) for the assessment of iron status in a population of anaemic pregnant women in Malawi. Stained bone marrow aspirates were used as the standard for comparison. Results show that for the purpose of screening, serum ferritin is the best single indicator of storage iron provided a cut-off point of 30 microg/l is used. A number of other commonly used parameters of iron status were shown to have limited diagnostic accuracy. Logistic regression was used to obtain mathematical models for the prediction of bone marrow iron status using a combination of available parameters.

Polynucleotide immunization of nonhuman primates against carcinoembryonic antigen

In preparation for a Phase I trial of DNA immunization against carcinoembryonic antigen (CEA) in patients with colorectal carcinoma, we have produced a single plasmid DNA encoding CEA and hepatitis B surface antigen (HBsAg) under transcriptional regulatory control of two separate cytomegalovirus promoters within separate eukaryotic expression cassettes, designated pCEA/HBsAg. Hepatitis B surface antigen was included to provide an internal positive control for the efficacy of this immunization strategy without regard to the issue of breaking tolerance to a self-antigen. In the present work, we sought to examine the immunogenicity of this plasmid in a nonhuman primate model with close phylogenetic relationship to humans. Groups of pig-tailed macaques were immunized with pCEA/ HBsAg by i.m. injection or particle bombardment of the skin according to a dose and schedule thought to be optimal for the respective technique of DNA immunization. Both administration techniques produced humoral and lympho-proliferative responses of comparable magnitude. However, delayed type hypersensitivity to CEA and CEA-specific interleukin-2 release were observed only in the i.m. group, suggesting a qualitative difference in the character of the immune response elicited by the two techniques of DNA immunization. The antibody responses to CEA and HBsAg were surprisingly persistent in that all immunized animals maintained moderate antibody titers against both antigens for more than 15 months after the last boost. No toxicity was observed during 2 years of follow-up, including no measurable levels of anti-DNA antibody. This antitumor immunization strategy is presently being examined in patients with metastatic colorectal carcinoma using pCEA/HBsAg administered by i.m. injection.

A cost-benefit comparison of self-expanding metal stents and Atkinson tubes for the palliation of obstructing esophageal tumors

This retrospective study was undertaken to assess the cost-benefit aspects of self expanding metal stents (SEMS), versus Atkinson Tubes (AT) in the palliation of obstructing esophageal tumors. Over a 4 year period, 50 patients received palliative endoscopic intubation for inoperable esophageal malignancy. Patients either received an AT or a newer, but more expensive, SEMS, both inserted under general anaesthetic. Both patients cohorts were assessed in terms of the severity of their dysphagia and scored according to Atkinson and Fergusons' classification both pre- and post-operatively. Other factors that were considered included length of hospital stay, number of interventions, admission to the Intensive Treatment Unit (ITU), and rates of post-operative complication. The majority of tumors were either adenocarcinoma or squamous cell carcinoma. The location of the tumors (upper, middle or lower) were similar in each group as was the mean length of tumor being 7 cms in SEMS and 5 cms in AT. There were significantly more complications in the AT group compared to the SEMS group (p < 0.05). The most common complications in the AT group were tube displacement (21%), tumor overgrowth (26%) and esophageal perforation (13%). In contrast complications of the SEMS group were tumor overgrowth (15%) and esophageal perforation (8%). Mean hospital stay was 3 (1-30) days for SEMS and 8 (2-122) days for AT (p < 0.05). The median total cost of hospital stay was 1745 pounds (1027-5424) for SEMS versus 2349 pounds (1163-24,481) for AT.

Involvement of products of the nrfEFG genes in the covalent attachment of haem c to a novel cysteine-lysine motif in the cytochrome c552 nitrite reductase from Escherichia coli

Cytochrome c552 is the terminal component of the formate-dependent nitrite reduction pathway of Escherichia coli. In addition to four 'typical' haem-binding motifs, CXXCH-, characteristic of c-type cytochromes, the N-terminal region of NrfA includes a motif, CWSCK. Peptides generated by digesting the cytochrome from wild-type bacteria with cyanogen bromide followed by trypsin were analysed by on-line HPLC MS/MS in parent scanning mode. A strong signal at mass 619, corresponding to haem, was generated by fragmentation of a peptide of mass 1312 that included the sequence CWSCK. Neither this signal nor the haem-containing peptide of mass 1312 was detected in parallel experiments with cytochrome that had been purified from a transformant unable to synthesize NrfE, NrfF and NrfG: this is consistent with our previous report that NrfE and NrfG (but not NrfF) are essential for formate-dependent nitrite reduction. Redox titrations clearly revealed the presence of high and low mid-point potential redox centres. The best fit to the experimental data is for three n=1 components with mid-point redox potentials (pH 7.0) of +45 mV (21% of the total absorbance change), -90 mV (36% of the total) and -210mV (43% of the total). Plasmids in which the lysine codon of the cysteine-lysine motif, AAA, was changed to the histidine codon CAT (to create a fifth 'typical' haem c-binding motif), or to the isoleucine and leucine codons, ATT and CTT, were unable to transform a Nrf deletion mutant to Nrf+ or to restore formate-dependent nitrite reduction to the transformants. The presence of a 50 kDa periplasmic c-type cytochrome was confirmed by staining proteins separated by SDS-PAGE for covalently bound haem, but the methyl-viologen-dependent nitrite reductase activities associated with the mutated proteins, although still detectable, were far lower than that of the native protein. The combined data establish not only that there is a haem group bound covalently to the cysteine-lysine motif of cytochrome c552 but also that one or more products of the last three genes of the nrf operon are essential for the haem ligation to this motif.

Mandibular distraction osteogenesis: a comparison of distraction rates in the rabbit model

The rabbit model has been used to study the effects of different rates of distraction upon mandibular bone. Bilateral distraction was performed at two different rates anterior to the molar teeth. Both experimental groups were significantly inferior to sham operated controls in terms of bone density (DEXA) and mechanical testing. No difference in new bone formation between the two distraction rates was detected by these modalities. However, histological examination revealed non-union to be more common in the rapidly distracted group. This suggests that attempts to shorten the duration of external fixation in clinical mandibular distraction osteogenesis should be by methods other than more rapid distraction.

Granulocyte-macrophage colony-stimulating factor induces activation and restores respiratory burst activity in monocytes from septic patients

Monocyte activation in response to recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) was examined in vitro in septic shock patients. These monocytes exhibited a greater respiratory burst activity than monocytes from healthy subjects; the response to secondary stimulation with bacterial stimuli was attenuated. GM-CSF restored the ability of monocytes to respond appropriately to secondary stimulation. Expression of certain integrin adhesion molecules, L-selectin, and Fcgamma receptors was increased on monocytes of septic shock patients; expression of CD11c was reduced. GM-CSF up-regulated integrin expression and decreased L-selectin, FcgammaRII, and FcgammaRIII expression. Septic patients exhibited greater biologic activity of monocyte tissue factor than did healthy subjects. Priming monocytes with GM-CSF accelerated tissue factor activation following stimulation with lipopolysaccharide and bacterial culture supernatant. Certain parameters of monocyte function may be restored by exposure to GM-CSF. This benefit may be offset by an increase in monocyte procoagulant activity.

Different treatment regimens to reduce microbial contamination of purified porcine islets of Langerhans

BACKGROUND

Different treatment regimens for minimizing microbial contamination of purified porcine islets were analyzed.

METHODS

Purified islets, prepared from abattoir-excised pancreata (n=26), were cultured in Hams F-12 with or without antibiotics after islet isolation. Aliquots of pancreas transport media were all contaminated with microbes (100%). Of those islets cultured with no antibiotics, 70% were contaminated, compared with 42% of the islets cultured in penicillin and streptomycin (P/S) (P>0.05). A further 20 consecutive pancreata were then randomized to saline washing (N=10) before islet isolation. Islets were then cultured in either Hams F-12 with P/S (groups C and E) or Hams F-12 with gentamicin, penicillin, and amphotericin B (G/P/A) (groups D and F).

RESULTS

None of those purified islets prepared from washed pancreata and then undergoing culture in Hams F-12 with G/P/A (group F) were contaminated. This compared with 30% contamination when islets were cultured in P/S (group E). Neither antibiotic regimen compromised stimulated insulin release (P=0.13).

CONCLUSIONS

In conclusion pancreas washing in saline and culture in G/P/A was shown to eradicate detectable microbial contamination of purified porcine islets isolated from abattoir-excised pancreata.

Stress and dominance in a social fish

Many aspects of reproductive physiology are subject to regulation by social interactions. These include changes in neural and physiological substrates of reproduction. How can social behavior produce such changes? In experiments reported here, we manipulated the social settings of teleost fish and measured the effect (1) on stress response as reflected in cortisol production, (2) on reproductive potential as measured in production of the signaling peptide, gonadotropin-releasing hormone, and (3) on reproductive function measured in gonad size. Our results reveal that the level of the stress hormone cortisol depends critically on both the social and reproductive status of an individual fish and on the stability of its social situation. Moreover, the reproductive capacity of an individual fish depends on these same variables. These results show that social encounters within particular social contexts have a profound effect on the stress levels as well as on reproductive competence. Social behavior may lead to changes in reproductive state through integration of cortisol changes in time. Thus, information available from the stress pathway may provide socially relevant signals to produce neural change.

Is Hartmann's the solution?

As Hartmann's solution is commonly used by anaesthetists, we surveyed a group of Part III FRCA candidates to establish their knowledge of its constituents and the purpose and metabolism of the lactate in solution. Of the 82 candidates surveyed only three (4%) accurately recorded the electrolytes and their concentrations in Hartmann's solution. Lactate was stated to be a source of bicarbonate by 52 (63%) and a source of glucose by 17 (21%). The descriptions of lactate metabolism were largely imprecise, none was complete and 24 (29%) of candidates offered no explanation. The constituents of Hartmann's solution and their concentrations are designed to match those of plasma, reducing ion and fluid shifts postinfusion. The lactate in Hartmann's solution is metabolised by both oxidation and gluconeogenesis, predominantly in the liver, and bicarbonate is generated by both processes over 1-2 h.

Lower limb amputation and grade of surgeon

BACKGROUND

The aim of this study was to identify clinical and operative risk factors that might influence the rate of independent ambulation following major limb amputation.

METHODS

Between 1989 and 1993, 172 patients had 193 lower limb amputations for peripheral vascular disease: 98 below-knee, 86 above-knee and nine through-knee.

RESULTS

The overall revision rate was 13.5 per cent. Revision was significantly more frequent in those patients who had a previous vascular reconstruction. Only 26 per cent of patients were able to ambulate independently after rehabilitation and limb-fitting. Univariate risk factor analysis suggested that independent ambulation was not affected by age, mode of presentation, the presence of ischaemic heart disease, diabetes, smoking status, previous vascular reconstruction or the level of amputation. However, fewer patients whose amputation was performed by a junior trainee could walk with a prosthetic limb (P = 0.03).

CONCLUSION

Patients considered suitable for walking training should have amputation performed by a senior trainee or consultant to optimize independent ambulation with a prosthetic limb.

RNA apatamers for yeast ribosomal protein L32 have a conserved purine-rich internal loop

Two in vitro selection experiments were conducted to determine the RNA sequence requirements for binding ribosomal protein L32 (RPL32) from Saccharomyces cerevisiae. To preserve the wild-type stem-internal loop-stem fold, only a limited portion of the RNA comprising the internal loop region was randomized. Most of the selected RNAs have secondary structures similar to that of the wild-type, and four purines on both sides of the internal loop are highly conserved. Indeed, a pair of 5'-GA-3' dinucleotides is found in all but one of the stem-loop-stem L32 aptamers and these conserved purines may contact the protein directly or form a necessary RNA secondary or tertiary structure. These aptamers have a potential G:U pair bordering the loop adjacent to the conserved GAs, but a cytidine replaces a phylogenetically conserved adenosine at one loop position in many of the selected RNAs. In model RNAs, the cytidine-bearing variant binds protein slightly more strongly than does the wild-type RNA. That the seven-member, 2 + 5 internal loop is important for protein binding is reinforced by the finding that the position, but not the size, of the loop is variable. A minority of the RNA aptamers has three consecutive uridines and may fold into a similar structure, but with the internal loop inverted.

Determination of lysergide in urine by high-performance liquid chromatography combined with electrospray ionisation mass spectrometry

A quantitative method which avoids derivatisation is described for the determination of lysergide (LSD) levels in urine. Sample preparation included addition of methysergide as an internal standard followed by solid-phase extraction. LSD was analysed on a system consisting of a C18 stationary phase and a mobile phase of 0.1 M acetate buffer pH 8.0-acetonitrile-triethylamine (75:25:0.25, v/v). LSD was detected by electrospray ionisation mass spectrometry with selected ion monitoring. The quantification limit was 0.5 ng/ml and the method was linear up to 10 ng/ml of LSD in urine.

Changing through doing: behavioral influences on the brain

It seems self-evident that the brain controls behavior but does behavior also "control" the brain? This chapter examines evidence that behavior can and does influence specific aspects of brain structure and function. Evidence for such influence is easily obtained on an evolutionary time scale, since the selective forces found in the ecological niche of the animal are typically reflected in its sensory and motor activities as well as its body shape and behavioral habits. Similarly, during development, there is ample evidence that the behavior acts in concert with the environment to establish structural changes in the brain that last a lifetime. Perhaps most surprisingly there is now evidence that social behavior can cause changes in the brain in adult animals and that these changes are reversible. The changes caused by behavioral interactions can be dramatic and typically are related to reproductive behavior. Understanding the mechanisms responsible for dynamic changes in the nervous systems of adult animals is a major challenge and the discovery that it can occur may lead to insights about other systems where behavior sculpts the brain.

The analysis of lysergide (LSD): the development of novel enzyme immunoassay and immunoaffinity extraction procedures together with an HPLC-MS confirmation procedure

A forensic procedure for the screening and confirmation of the presence of lysergide (lysergic acid diethylamide, LSD) in urine is described together with the evaluation of a novel enzyme immunoassay (EIA) and immunoaffinity extraction procedure. Following initial screening using either an established radioimmunoassay (RIA) or a novel EIA procedure, a quantitative estimate is established using a conventional high performance liquid chromatography-fluorescence (HPLC) technique following solid phase extraction. Final confirmation and quantitation, without derivatization, is established using HPLC in combination with electrospray ionization (ESI) mass spectrometry using methysergide as an internal standard. The detection limit of LSD in urine is 0.5 ng/mL. A blind trial confirmed the validity of the results. The choice of internal standard is discussed. Consideration is given to the photosensitivity of LSD solutions. A study of potential interferants in the HPLC-MS confirmation of LSD is presented and shows that for the wide range of compounds studied, there are none that would interfere with this confirmation technique. A comparison is shown between solid phase and immunoaffinity extraction/clean up procedures, and between RIA and EIA screening procedures.

Influence of different collagenase solvents and timing of their delivery on porcine islet isolation

Methods to minimize the effect of cold ischaemia on porcine islet isolation were investigated. Forty pancreata were randomized to intraductal collagenase delivery in University of Wisconsin solution (UW) or Hanks balanced salt solution (HBSS) (control) both before and after 65 min of cold pancreas storage. Collagenase was also administered in a specially designed cold storage solution (University of Leicester solution, ULEIC), before cold storage. Median islet yield was significantly greater if the pancreas was distended with collagenase in either UW (21524 islet equivalents (IEQ) per g) or ULEIC (19814 IEQ/g) before cold storage, compared with that after distension with HBSS (6924 IEQ/g) following cold storage (P < 0.05). Islet fragmentation, islet purification and glucose-stimulated insulin release were not significantly different after collagenase delivery in either UW or ULEIC compared with those after administration in HBSS. It is concluded that porcine islet yields can be improved significantly by intraductal collagenase administration in either UW or ULEIC immediately after excision of the pancreas.

Characterization of two new preproGnRH mRNAs in the tree shrew: first direct evidence for mesencephalic GnRH gene expression in a placental mammal

Reproductive maturation and regulation is centrally orchestrated by gonadotropin-releasing hormone (GnRH). GnRH produced in the vertebrate hypothalamus acts on the pituitary to regulate gonadotropins. In nonplacental mammalian species, it has recently been shown that a second GnRH gene is expressed in mesencephalic cells. Here, we report the cDNA sequences and expression patterns for two distinct genes encoding the hypothalamic and mesencephalic GnRH forms in the brain of a placental mammal, the tree shrew (Tupaia glis belangeri). The novel mammalian GnRH form, designated here as [His5Trp7Tyr8]GnRH (often called chicken GnRH II), is expressed in neurons of the mesencephalon and is the first nonhypothalamic form to be isolated from a mammal. Its peptide sequence is identical to the form previously reported in fish, amphibians, reptiles, and birds, revealing that it has remained unchanged for 500 million years. In contrast, the sequences of the hypothalamic GnRH decapeptides vary by as much as 50% across vertebrate species. The remarkable sequence conservation of mesencephalic GnRH suggests that it has been highly constrained throughout evolution, perhaps indicating an important, conserved nongonadotropic role. The discovery and localization of two mRNAs encoding distinct GnRH forms in an advanced mammal suggest that other mammals, including primates, may also have a second GnRH gene with expression localized in the midbrain.

Anaesthesia with the Boyle's bottle vaporizer

Having used the Boyle's bottle vaporizer apparatus out of necessity in a developing country, the concentration of agent that had been administered was investigated retrospectively. Three anaesthetic agents, halothane, isoflurane and enflurane, were measured at different temperatures, using a Boyle's anaesthetic machine and a Boyle's bottle in circuit with a Magill breathing system connected to a Rascal II Agent Monitor. Bubbling a fresh gas flow of 5 l.min-1 through the anaesthetic liquids generated concentrations in excess of 12%. Elevating the initial temperature of the vaporizer increased the delivered concentration, although this effect was short-lived. Therapeutic concentrations of vapour were achieved for all three agents by avoiding bubbling and manipulating the 'splitting ratio' lever. The Boyle's bottle vaporizer may be used with modern anaesthetic agents such as halothane, isoflurane and enflurane. However, the limitations of and variations between vaporizers should be borne in mind. An agent monitor employed at the patient end of the circuit would be an important safety feature.

Two-Day Hydrophobic Grid Membrane Filter Method for Yeast and Mold Enumeration in Foods Using YM-11 Agar: Collaborative Study

Twenty laboratories participated in a collaborative study to validate a 2-day hydrophobic grid membrane filter method using YM-11 agar for enumeration of yeast and mold in foods. Six naturally contaminated food products were included in the study: garlic powder, raw ground beef, walnuts, flour/meal, orange juice, and yogurt. The test method produced significantly higher results than the 5-day pour plate reference method for orange juice and significantly lower, though numerically similar, results for walnuts and yogurt. Differences between the test and reference methods were not significant for garlic powder, raw ground beef, or flour/meal. Repeatability and reproducibility were similar for both the test and reference methods in all cases. The hydrophobic grid membrane filter method for enumeration of yeast and mold in foods has been adopted by AOAC INTERNATIONAL.

A complication of indoor pistol shooting

The aetiology of chronic rhinitis and nasal obstruction is often elusive and obscure. Many different causes have been documented including allergens, cigarette smoke, cold dry air, viruses, sulphur dioxide and industrial pollutants. This is the first case we have been able to identify of rhinitis associated with exposure to high levels of lead through indoor pistol shooting.

Determination of the gene sequence and the three-dimensional structure at 2.4 angstroms resolution of methanol dehydrogenase from Methylophilus W3A1

The DNA sequences for the genes encoding the heavy and light subunits of methanol dehydrogenase from Methylophilus methylotrophus W3A1 have been determined. The deduced amino acid sequence has enabled the structure of the enzyme to be refined at 2.4 angstrom resolution against X-ray data collected on a Hamlin area detector. The structure was refined using the programs PROFFT and X-PLOR with several model building step interspersed. The final model contains two heavy chains (571 amino acids), two light chains (69 amino acids), two molecules of pyrroloquinoline quinone, two Ca2+ and 521 solvent molecules. Each half molecule contains four disulfide linkages and four cis peptides. One of the disulfides is formed from two adjacent cysteine residues linked by a trans peptide which creates a novel eight-membered ring. The heavy subunit is an 8-fold beta-propeller, each "blade" of which is a four-stranded antiparallel twisted beta-sheet. The light chain is an elongated subunit stretching across the surface of the heavy subunit, with residues 1 to 32 containing four beta-turns and residues 33 to 62 forming a helix; however, it neither interacts with the active site, nor the other HL dimer and its functional role is obscure. Around the 8-fold beta-propeller there is a repeating pattern of tryptophan residues located in the outer strand of seven of the eight beta-leaflets, each packed between adjacent leaflets. Each of these tryptophan residues is centered in the beta-strand and participates in the main chain hydrogen bonding of the sheet. Five of the seven tryptophan residues have closely similar interactions with the adjacent beta-leaflet including stacking of the tryptophan indole rings against a peptide plane and formation of a hydrogen bond from NE1 of the indole ring to a main-chain carbonyl. This repeating pattern is conserved over a number of MEDH sequences. The PQQ is located on the pseudo 8-fold rotation axis of the heavy subunit, in a funnel-shaped internal cavity, sandwiched between the indole ring of Trp237 and the two sulfur atoms of the Cys103-Cys104 vicinal disulfide. A hexacoordinate Ca2+ is bound in the active site by one nitrogen and five oxygen ligands, three from the PQQ and the others from two protein side-chains. In the active site an isolated solvent molecule is bound to the O5 of PQQ and to a nearby aspartate side-chain; its position may be the binding site for methanol. The aspartate might than serve as a general base for proton abstraction from the substrate hydroxyl. The C5 atom of PQQ could be activated by electrophilic catalysis by a nearby argenine side-chain or by the calcium ion bound to PQQ.

Laparoscopic gastrectomy: five cases

We present the results of five patients who underwent gastrectomy using a laparoscopic technique. All patients had an intracorporeal resection of the antrum followed by an antecolic intracorporeal gastrojejunostomy (Billroth II). Two patients also had bilateral truncal vagotomy, and one had a Roux-en-Y component to the gastrojejunostomy. Indications were (a) intractable ulcer disease in two patients; (b) gastric outlet obstruction due to duodenal ulcer in one; (c) chronic, severe gastrointestinal blood loss from bile reflux gastritis in one; and (d) palliation of a superficial carcinoma in one. Except for one patient who had postoperative gastric atony, there were no complications or operative mortality. Short-term follow-up ranging from 9 to 34 months has revealed one patient with recurrent ulcer symptoms, but the other four have had control of their disease.

Yeast ribosomal protein L32 recognizes an RNA G:U juxtaposition

Yeast ribosomal protein L32, RPL32, specifically represses splicing by binding to a purine-rich asymmetric loop adjacent to the 5' splice site of its own transcript. A potential G:U pair closes the internal loop and the goal of the present study is to understand what features of the putative G:U pair are recognized by RPL32. Two RNA oligomers containing 10 and 13 nt were annealed to form a bimolecular stem-loop-stem protein-binding site. Protein binding to each of 16 sequence variants was examined using electrophoretic bandshift and filter-binding experiments. The proteins binds to only the duplex RNA and not to the individual oligomers, and the G:U pair is critical for full-strength binding. Mutational studies show that the duplex having a G:U has the highest protein affinity (Kd = 10 nM), followed by RNAs bearing G:A, C:C, U:A, U:C, or G:G. Duplexes containing the other possible pairs bind very weakly and Watson-Crick pairing does not favor protein binding. The G of the G:U is required for strong protein binding, but replacement by inosine reduces binding only modestly. Therefore, the minor groove guanine amino group is not a key protein recognition element. Both nucleotides of the pair influence the binding strength, but their contributions are in general not additive. These data imply that the G:U is probably paired and influences binding indirectly through its effect on the conformation of the RNA.

Laparoscopic colon resection: 60 cases

The first 60 successfully completed laparoscopic colectomies in our series are reported. Patients used moderate amounts of narcotic postoperatively, tolerated oral intake early postoperatively (mean, 1.5 days), and returned to work 2.5 weeks postoperatively. Mean blood loss was 127 cc. Morbidity (11.6%) and mortality (1.6%) were acceptable. Length of stay, complications, and operating time all decreased with experience suggesting a steep learning curve.

Protein recognition of ammonium cations using side-chain aromatics: a structural variation for secondary ammonium ligands

A model for the structure of dimethylamine dehydrogenase was generated using the crystal coordinates of trimethylamine dehydrogenase. Substrate is bound in trimethylamine dehydrogenase by cation-pi bonding, but modeling of dimethylamine dehydrogenase suggests that secondary amines are bound by a mixture of cation-pi and conventional hydrogen bonding. In dimethylamine dehydrogenase, binding is orientationally more specific and distinct from those proteins that bind tertiary and quaternary amine groups.

Comparison of the effects of propofol and isoflurane anaesthesia on right ventricular function and shunt fraction during thoracic surgery

I.v. anaesthetic agents, including propofol, have not been shown to inhibit hypoxic pulmonary vasoconstriction (HPV). This may encourage the use of propofol in thoracic surgery where one lung ventilation (OLV) is required. We have compared the effects of maintaining anaesthesia with either isoflurane or propofol infusion on right ventricular function and shunt fraction. We studied 10 patients who received isoflurane and 12 who received propofol. When OLV commenced there was a greater reduction in both mean cardiac index (3.2 (SEM 0.2) to 2.4 (0.1) litre min-1 m-2 for propofol, and 3.4 (0.2) to 3.3 (0.4) litre min-1 m-2 for isoflurane) and right ventricular ejection fraction (0.45 (0.03) to 0.37 (0.02) for propofol, and 0.48 (0.02) to 0.42 (0.02) for isoflurane) in patients who received propofol. Furthermore, these reductions were sustained for longer in the propofol group. However, propofol was not associated with a significant increase in shunt fraction during OLV, which increased threefold in patients who received isoflurane.

A thermodynamic and mutational analysis of an RNA purine loop as a protein binding site

The thermal stability and protein binding of a 36 nucleotide RNA hairpin containing an internal loop were studied under various solution conditions. Yeast ribosomal protein L32 binds to its transcript and small RNAs which reproduce the L32 transcript's secondary structure have been examined. Replacement of the internal loop with canonical base pairs did not affect the salt dependence of the melting temperature suggesting that both molecules adopt a linear shape. Several electrostatic contacts are formed on binding to a ribosomal fusion protein, but Mg+2 is not required for binding. The RNA protein complex is stable up to 50 degrees C. Two internal loop deletion mutants have similar thermodynamic stabilities and chemical and enzymatic reactivities, but fail to bind the fusion protein. However, several of the internal loop bases of the deletion mutants are moderately reactive to chemical agents whereas the wild type loop sequence displayed a mixed pattern of protection and hyperreactivity.

Three gonadotropin-releasing hormone genes in one organism suggest novel roles for an ancient peptide

Gonadotropin-releasing hormone (GnRH) is known and named for its essential role in vertebrate reproduction. Release of this decapeptide from neurons in the hypothalamus controls pituitary gonadotropin levels which, in turn, regulate gonadal state. The importance of GnRH is underscored by its widespread expression and conservation across vertebrate taxa: five amino acids are invariant in all nine known forms, whereas two others show only conservative changes. In most eutherian mammals, only one form, expressed in the hypothalamus, is thought to exist, although in a recent report, antibody staining in developing primates suggests an additional form. In contrast, multiple GnRH forms and expression loci have been reported in many non-mammalian vertebrates. However, evidence based on immunological discrimination does not always agree with analysis of gene expression, since GnRH forms encoded by different genes may not be reliably distinguished by antibodies. Here we report the expression of three distinct GnRH genes in a teleost fish brain, including the sequence encoding a novel GnRH preprohormone. Using in situ hybridization, we show that this form is found only in neurons that project to the pituitary and exhibit changes in soma size depending on social and reproductive state. The other two GnRH genes are expressed in other, distinct cell populations. All three genes share the motif of encoding a polypeptide consisting of GnRH and a GnRH-associated peptide. Whereas the GnRH moiety is highly conserved, the GnRH-associated peptides are not, reflecting differential selective pressure on different parts of the gene. GnRH forms expressed in nonhypothalamic regions may serve to coordinate reproductive activities of the animal.

Characterization of the pre-mRNA binding site for yeast ribosomal protein L32: the importance of a purine-rich internal loop

The structure of the RNA binding target for Saccharomyces cerevisiae ribosomal protein L32 was examined using chemical and enzymatic probes as well as thermodynamic methods. In vivo, the production of yeast RPL32 is regulated by a feedback mechanism whereby RPL32 binds to the 5' end of its transcript and inhibits splicing. The binding site of ribosomal protein L32 on the L32 RNA transcript can be reduced to fewer than 30 nucleotides which compromise a stem-internal loop-stem structural motif. The internal loop is closed by a potential G-U pair, is asymmetric and contains mostly purines. The existence of the two helical regions was confirmed by chemical and enzymatic probing. The reactivity of the loop region suggests a structure intermediate between that of single and double-stranded RNA. Base stacking continues into the loop, but two loop bases are extremely reactive to chemical agents. The interaction between the model RNA and the protein is specific and has a dissociation constant of approximately 10 nM. Several of the loop bases are critical for protein binding, as demonstrated by mutational data and chemical protection and modification interference studies. The internal loop destabilizes the RNA, and allows the RNA to melt in an all-or-none fashion.

Risk factors leading to arterial occlusion following diagnostic arteriography

OBJECTIVES

Arteriography may precipitate occlusive complications in stenotic vessels by a toxic effect on the vascular endothelium, leading to intra-arterial thrombosis. The aim of this retrospective study was to determine the incidence of arterial occlusion following arteriography.

METHODS

We studied 101 consecutive patients (71 male, 30 female; median age 72 years) undergoing percutaneous transluminal angioplasty (PTA) of stenotic lesions, which had been identified on diagnostic arteriograms performed a median of 109 days (range 6-519) previously. One hundred and thirty-one arterial stenoses suitable for PTA were identified in the patient cohort.

RESULTS

Seventeen patients (17%) progressed to occlusion in the period between diagnostic arteriography and PTA. Stenoses in the femoro-popliteal segment (21%) progressed to occlusion more frequently than lesions of the iliac arteries (3%). Independent risk factors were analysed to determine the risk factors predisposing to arterial occlusion following diagnostic arteriography. Both groups were well matched for age and sex. The mode of presentation, the presence of ischaemic heart disease, hypertension, diabetes or current smoking habits did not predict progression of disease to arterial occlusion. However, the rate of occlusion appeared to be influenced by the proportion of patients taking anti-platelet medication (51% in non-occluders as compared to 11% in patients who occluded, 95% CI 0.1 to 10), and to the length of time between arteriography and PTA (median of 92 days in non-occluders as compared to 125 days in patients who occluded, 95% CI 21 to 57).

CONCLUSIONS

These data demonstrate that occlusion of pre-existing arterial stenoses following diagnostic arteriography is significantly more frequent in patients not taking anti-platelet medication and when the time interval between arteriography and PTA exceeds 92 days. To minimise thrombotic arterial occlusion both diagnostic and therapeutic procedures should be performed simultaneously, but if a delay is unavoidable, patients should be treated with anti-platelet medication, which reduces the incidence of arterial occlusion.