Biasing vector network analyzers using variable frequency and amplitude signals

We report the development of a test setup designed to provide a variable frequency biasing signal to a vector network analyzer (VNA). The test setup is currently used for the testing of liquid crystal (LC) based devices in the microwave region. The use of an AC bias for LC based devices minimizes the negative effects associated with ionic impurities in the media encountered with DC biasing. The test setup utilizes bias tees on the VNA test station to inject the bias signal. The square wave biasing signal is variable from 0.5 to 36.0 V peak-to-peak (VPP) with a frequency range of DC to 10 kHz. The test setup protects the VNA from transient processes, voltage spikes, and high-frequency leakage. Additionally, the signals to the VNA are fused to ½ amp and clipped to a maximum of 36 VPP based on bias tee limitations. This setup allows us to measure S-parameters as a function of both the voltage and the frequency of the applied bias signal.

Culturally adapting the prevention of diabetes and obesity in South Asians (PODOSA) trial

Type 2 diabetes is extremely common in South Asians, e.g. in men from Pakistani and Indian populations it is about three times as likely as in the general population in England, despite similarities in body mass index. Lifestyle interventions reduce the incidence of diabetes. Trials in Europe and North America have not, however, reported on the impact on South Asian populations separately or provided the details of their cross-cultural adaptation processes. Prevention of diabetes and obesity in South Asians (PODOSA) is a randomized, controlled trial in Scotland of an adapted, lifestyle intervention aimed at reducing weight and increasing physical activity to reduce type 2 diabetes in Indians and Pakistanis. The trial was adapted from the Finnish Diabetes Prevention Study. We describe, reflect on and discuss the following key issues: The core adaptations to the trial design, particularly the delivery of the intervention in homes by dietitians rather than in clinics. The use of both a multilingual panel and professional translators to help translate and/or develop materials. The processes and challenges of phonetic translation. How intervention resources were adapted, modified, newly developed and translated into Urdu and Gurmukhi (written Punjabi). The insights gained in PODOSA (including time pressures on investigators, imperfections in the adaptation process, the power of verbal rather than written information, the utilization of English and the mother-tongue languages simultaneously by participants and the costs) might help the research community, given the challenge of health promotion in multi-ethnic, urban societies.

A broadband ferromagnetic resonance spectrometer to measure thin films up to 70 GHz

We report the development of a broadband ferromagnetic resonance (FMR) system operating in the frequency range from 10 MHz to 70 GHz using a closed-cycle He refrigeration system for measurements of thin films and micron/nano structures. The system is capable of carrying out measurements in frequency and field domain. Using two coplanar waveguides, it is capable of simultaneously measuring two samples in the out of plane and in plane FMR geometries. The system operates in the temperature range of 27-350 K and is sensitive to less than one atomic monolayer of a single crystal Fe film.

Small intestinal infarction: a fatal complication of systemic oxalosis

Primary hyperoxaluria is a rare genetic disorder characterised by calcium oxalate nephrolithiasis and nephrocalcinosis leading to renal failure, often with extra-renal oxalate deposition (systemic oxalosis). Although ischaemic complications of crystal deposition in vessel walls are well recognised clinically, these usually take the form of peripheral limb or cutaneous ischaemia. This paper documents the first reported case of fatal intestinal infarction in a 49 year old woman with systemic oxalosis and advocates its consideration in the differential diagnosis of an acute abdomen in such patients.

A review of food provision to a renal ward and the proposed appointment of feeding assistants

Malnutrition among renal patients has been widely documented and is associated with increased morbidity and mortality. Advances in dialysis technology and transplantation have helped to increase patient long-term survival, and as more elderly patients commence dialysis programs, the problem of malnutrition is escalating. Hospitalized renal patients are at a greater risk, as dietary intakes may be reduced for a number of reasons. A multidisciplinary team decided to review the existing cook-chill plated meal system and all food provision to the renal ward. The aim of this review was to assess the nutritional intake of renal inpatients and to gauge patients' and relatives' attitudes towards hospital food provision. From these results, we hoped to go on and implement some changes to help improve the situation. Results showed that 34% of the patients ate half or less of the hospital food provided, and 80% of patients surveyed relied on food brought in by relatives and friends. Actual dietary intakes were compared to Dietary Reference Values (DRVs; Department of Health [DoH], UK, 1995). One hundred percent of the patients did not achieve the DRVs for energy, iron, potassium, zinc, folate, B6, and riboflavin. Sixty-six percent of the patients did not achieve the DRV for protein. These results were discussed by the multidisciplinary group, and it was decided to trial a cook-chill bulk trolley to replace the existing plated meal system. Unfortunately, to implement a bulk trolley system, the ward needs someone to serve the food. This could be the job of a "feeding assistant" or "ward hostess." A bid has been put forward to the hospital Trust Board to obtain funding for these "feeding assistants, " and the bulk trolley can be acquired from existing funds. It is hoped that the creation of these new posts will go some of the way towards improving the patients' dietary intake while in the hospital.

The repositioning of migrated Tenckhoff continuous ambulatory peritoneal dialysis catheters under fluoroscopic control

We describe a non-invasive, simple technique which, under fluoroscopic control, repositions migrated Tenckhoff CAPD catheters back into the pelvis. 18 patients, who had a total of 23 manipulations, were studied retrospectively over 2 1/2 years. Technical success (successful repositioning of the catheter at screening) and clinical success (continued effective CAPD for at least 6 months thereafter) were obtained in 84% and 45% of patients respectively. The results showed this technique to be effective in restoring the correct catheter position in CAPD patients whose catheters have migrated. Clinical success was more likely to be achieved in patients who had fewer risk factors for the development of peritoneal adhesions. The use of custom-made stainless steel wires eased manipulations and significantly reduced the radiation dose to patient and operator from the procedure.

Motor innervation of the cricopharyngeus muscle by the recurrent laryngeal nerve

Patients with recurrent laryngeal nerve (RLN) paresis demonstrate impaired function of laryngeal muscles and swallowing. The cricopharyngeus muscle (CPM) is a major component of the upper esophageal sphincter. It was hypothesized that the RLN innervates this muscle. A nerve branch leading from the RLN to the CPM was found in adult sheep by anatomic dissection. Electrical stimulation of the RLN elicited a muscle action potential recorded by electrodes placed in the ipsilateral CPM. Swallowing was investigated by mechanical stimulation of oropharynx pre- and postsectioning of the RLN. Severing of the RLN resulted in a loss of the early phases of swallow-related CPM electromyographic activity; however, late-phase CPM electromyographic activity persisted. The RLN provides motor innervation of the CPM, which also has innervation from the pharyngeal plexus.

2-Phenyl-4-(aminomethyl)imidazoles as potential antipsychotic agents. Synthesis and dopamine D2 receptor binding

A series of 2-phenyl-4-(aminomethyl)imidazoles were designed as conformationally restricted analogs of the dopamine D2 selective benzamide antipsychotics. The title compounds were synthesized and tested for blockade of [3H]YM-09151 binding in cloned African green monkey dopamine D2 receptor preparations. The binding affinity data thus obtained were compared against that of the benzamides and a previously described series of 2-phenyl-5-(aminomethyl)-pyrroles.

Risk factors for non-ischaemic foot ulceration in diabetic nephropathy

It is recognized that diabetic patients with nephropathy frequently have macrovascular disease leaving them at risk of ischaemic foot lesions. In order to assess non-vascular risk factors for foot ulceration 64 patients were stratified into four groups: microalbuminuria, albuminuria with creatinine clearance greater than 40 ml min-1, chronic renal failure (clearance less than 40 ml min-1), and a non-nephropathic diabetic control group. Vibration perception threshold was measured by biothesiometry, peroneal nerve conduction velocity by conventional methods, and dynamic foot pressure by pedobarography. Vibration perception threshold was elevated in all three groups when compared with age-matched normal and diabetic control groups. Mean vibration perception threshold was 20.8 +/- 8.6 (+/- SD) in the microalbuminuria group (p less than 0.001 compared with age-matched normal control group), 28.1 +/- 5.6 (p less than 0.001) in the albuminuria group, 38.9 +/- 9.4 (p less than 0.001) in the renal failure group, 14.8 +/- 5.2 in the diabetic control group and 12.3 +/- 2.9 in the normal control group. Peroneal motor conduction velocity was reduced in all three groups when compared with normal control subjects, microalbuminuria 38.6 +/- 4.2 m s-1 (p less than 0.001), albuminuria 38.0 +/- 6.1 m s-1 (p less than 0.01), renal failure 35.5 +/- 1.2 m s-1 (p less than 0.001), diabetic control 40.6 +/- 1.8 m s-1, and normal 43.1 +/- 2.3 m s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Penicillin-resistant viridans streptococci have obtained altered penicillin-binding protein genes from penicillin-resistant strains of Streptococcus pneumoniae

Penicillin-resistant strains of Streptococcus pneumoniae possess altered forms of penicillin-binding proteins (PBPs) with decreased affinity for penicillin. The PBP2B genes of these strains have a mosaic structure, consisting of regions that are very similar to those in penicillin-sensitive strains, alternating with regions that are highly diverged. Penicillin-resistant strains of viridans groups streptococci (e.g., S. sanguis and S. oralis) that produce altered PBPs have also been reported. The PBP2B genes of two penicillin-resistant clinical isolates of S. sanguis were identical in sequence to the mosaic class B PBP2B genes found in penicillin-resistant serotype 23 strains of S. pneumoniae. Emergence of penicillin resistance appears to have occurred by the horizontal transfer of an altered PBP2B gene from penicillin-resistant S. pneumoniae into S. sanguis. The PBP2B genes of three penicillin-resistant S. oralis strains were similar to the mosaic class B PBP2B gene of penicillin-resistant strains of S. pneumoniae but possessed an additional block of diverged sequence. Penicillin resistance in S. oralis has also probably arisen by horizontal transfer of this variant form of the class B mosaic PBP2B gene from a penicillin-resistant strain of S. pneumoniae.

Horizontal transfer of penicillin-binding protein genes in penicillin-resistant clinical isolates of Streptococcus pneumoniae

Resistance to penicillin in clinical isolates of Streptococcus pneumoniae has occurred by the development of altered penicillin-binding proteins (PBPs) that have greatly decreased affinity for the antibiotic. We have investigated the origins of penicillin-resistant strains by comparing the sequences of the transpeptidase domain of PBP2B from 6 penicillin-sensitive and 14 penicillin-resistant strains. In addition we have sequenced part of the amylomaltase gene from 2 of the sensitive and 6 of the resistant strains. The sequences of the amylomaltase gene of all of the strains and of the PBP2B gene of the penicillin-sensitive strain show that S. pneumoniae is genetically very uniform. In contrast the PBP2B genes of the penicillin-resistant strains show approximately equal to 14% sequence divergence from those of the penicillin-sensitive strains and the development of penicillin resistance has involved the replacement, presumably by transformation, of the original PBP2B gene by a homologous gene from an unknown source. This genetic event has occurred on at least two occasions, involving different sources, to produce the two classes of altered PBP2B genes found in penicillin-resistant strains of S. pneumoniae. There is considerable variation among the PBP2B genes of the resistant strains that may have arisen by secondary transformation events accompanied by mismatch repair subsequent to their original introductions into S. pneumoniae.

Recruitment of a penicillin-binding protein gene from Neisseria flavescens during the emergence of penicillin resistance in Neisseria meningitidis

Non-beta-lactamase-producing, penicillin-resistant strains of Neisseria meningitidis produce altered forms of penicillin-binding protein 2 that have decreased affinity for penicillin. The sequence of the penicillin-binding protein 2 gene (penA) from a penicillin-resistant strain of N. meningitidis was compared to the sequence of the same gene from penicillin-sensitive strains and from penicillin-sensitive and penicillin-resistant strains of Neisseria gonorrhoeae. The penA genes from penicillin-sensitive strains of N. gonorrhoeae and N. meningitidis were 98% identical. The gene from the penicillin-resistant strain of N. meningitidis consisted of regions that were almost identical to the corresponding regions in the penicillin-sensitive strains (less than 0.2% divergence) and two regions that were very different from them (approximately 22% divergence). The two blocks of altered sequence have arisen by the replacement of meningococcal sequences with the corresponding regions from the penA gene of Neisseria flavescens and result in an altered form of penicillin-binding protein 2 that contains 44 amino acid substitutions and 1 amino acid insertion compared to penicillin-binding protein 2 of penicillin-sensitive strains of N. meningitidis. A similar introduction of part of the penA gene of N. flavescens, or a very similar commensal Neisseria species, appears to have occurred independently during the development of altered penA genes in non-beta-lactamase-producing penicillin-resistant strains of N. gonorrhoeae.

2H-[1]benzopyrano[3,4-b]pyridines: synthesis and activity at central monoamine receptors

Two general synthetic approaches to a novel series of 2H-[1]benzopyrano[3,4-b]pyridines are described together with their receptor binding profile at a variety of monoamine receptors in mammalian brain tissue. The biologically active members of this series fall into into one of two broad classes: 3,4,4a,5-tetrahydro-2H-[1]benzopyrano[3,4-b]pyridines or trans-1,3,4,4a,5,10b-hexahydro-2H-[1]benzopyrano[3,4-b]pyridines. By appropriate pharmacophoric modification potent selective ligands for D2, alpha-2, 5HT1A, and 5HT2 receptors may be obtained. The previously published in vivo data on certain key representatives of these series are also summarized.

How sensitive are immunometric assays for thyrotropin?

The usual method for calculation of the "sensitivity" of thyrotropin immunometric assays is multireplicate analysis of the zero analyte standard. Although this is a statistically valid estimate of the scatter likely to be found in the response variable, it is unrelated to normal analytical practice (usually analysis in duplicate) and estimates intra-assay errors only. This study was designed to assess the analytical performance of 10 immunometric assays used routinely for measurement of thyrotropin in human serum. Response data from each assay were accumulated to provide (a) an estimate of "sensitivity" from multireplicate analysis and (b) an estimate of "minimum detection limit," relating directly to errors associated with routine performance and derived from a minimum of 500 duplicate analyses. We conclude that the "minimum detection limit" should be promoted as a more meaningful measure of assay performance at low analyte concentrations than the "sensitivity" derived from multireplicate analysis of the zero-analyte standard.

How sensitive are immunometric assays for thyrotropin?

The usual method for calculation of the "sensitivity" of thyrotropin immunometric assays is multireplicate analysis of the zero analyte standard. Although this is a statistically valid estimate of the scatter likely to be found in the response variable, it is unrelated to normal analytical practice (usually analysis in duplicate) and estimates intra-assay errors only. This study was designed to assess the analytical performance of 10 immunometric assays used routinely for measurement of thyrotropin in human serum. Response data from each assay were accumulated to provide (a) an estimate of "sensitivity" from multireplicate analysis and (b) an estimate of "minimum detection limit," relating directly to errors associated with routine performance and derived from a minimum of 500 duplicate analyses. We conclude that the "minimum detection limit" should be promoted as a more meaningful measure of assay performance at low analyte concentrations than the "sensitivity" derived from multireplicate analysis of the zero-analyte standard.

Extensive re-modelling of the transpeptidase domain of penicillin-binding protein 2B of a penicillin-resistant South African isolate of Streptococcus pneumoniae

Clinical isolates of Streptococcus pneumoniae that have greatly increased levels of resistance to penicillin (greater than 1000-fold) have been reported from South Africa during the last ten years. Penicillin resistance in these strains is entirely due to the development of penicillin-binding proteins (PBPs) with decreased affinity for penicillin. We have cloned and sequenced the coding region for the transpeptidase domain of penicillin-binding protein 2B from three penicillin-sensitive strains of S. pneumoniae and from a penicillin-resistant South African strain. The amino acid sequences of the transpeptidase domains of PBP2B of the three penicillin-sensitive strains were identical and there were only between one and four differences in the nucleotide sequences of their coding regions. The corresponding region of the PBP2B gene from the penicillin-resistant strain differed by 74 nucleotide substitutions which resulted in 17 alterations in the amino acid sequence of PBP2B. The most remarkable alteration that has occurred during the development of the 'penicillin-resistant' form of PBP2B is the substitution of seven consecutive residues in a region that is predicted to form a loop at the bottom of the penicillin-binding site.

Inhibition of nigrostriatal release of dopamine in the rat by adenosine receptor agonists: A1 receptor mediation

The stable analogues of adenosine, N-ethylcarboxamidoadenosine (NECA), R-phenylisopropyladenosine (R-PIA) and cyclohexyladenosine (CHA), dose-dependently decreased levels of 3-methoxytyramine (3-MT) in the striatum and antagonized pargyline-dependent accumulation of 3-methoxytyramine. These agents were equipotent with ED25 values of approximately 1 mg/kg, (p.o.) in inhibiting pargyline-dependent accumulation of 3-methoxytyramine. Since CHA and R-PIA are relatively selective for A1 receptors and NECA is almost equipotent at A1 and A2 sites, the data of undifferentiated potency for these 3 agents on release of dopamine (levels of 3-MT) would argue in favor of mediation of A1 receptors in this phenomenon. This conclusion was further supported by experiments with the A1-selective antagonist, 8-cyclopentyl-1,3-dipropylxanthine (CPDX), which antagonized the actions of CHA. Similar antagonism of CHA-dependent decreases in levels of cyclic GMP in the cerebellum, an action known to be mediated by A1 receptors, was also observed. These data support previous studies which indicated an adenosine receptor-mediated modulation of nigrostriatal release of dopamine. In addition, the present data indicate that this is an action on A1 receptors.

CGS 19755 is a potent and competitive antagonist at NMDA-type receptors

The N-Methyl-D-aspartate (NMDA)-type receptor blocking properties of CGS 19755, a novel, rigid analog of 2-amino-5-phosphonopentanoate, were demonstrated in vitro by the ability of the compound to block NMDA-evoked [3H]acetylcholine release (pA2 = 5.93). CGS 19755 (0.045 and 0.224 mmol/kg i.p.) was shown to be active in vivo as well by its ability to block harmaline-induced increases in cerebellar cGMP. Finally, CGS 19755 blocked sound-induced seizures in DBA/2 mice completely at doses of 1.0 nmol i.c.v. or 0.1 mmol/kg i.p. Taken together, these data indicate that CGS 19755 is a potent and competitive NMDA antagonist in vitro which is also active in vivo.

Sequence analysis of ARS elements in fission yeast

Chromosomal DNA of Schizosaccharomyces pombe contains sequences with properties analogous to ARS elements of Saccharomyces cerevisiae. Following Sau3A fragmentation of the S. pombe genome we have recovered a number of such fragments in an M13-based shuttle vector, suitable for subsequent sequence analysis. The complete nucleotide sequence has been obtained for eight ARS+ inserts derived from the Sau3A cloning and for the ARS present in pFL20 isolated previously by Losson and Lacroute (Cell, 32, 371-377, 1983). The Sau3A clones are single fragments between 0.8 and 1.8 kb. No ARS+ clones smaller than this were recovered even though the average size Sau3A fragment in S. pombe is approximately 200-300 bp. The sequence analysis revealed that all clones are AT-rich (69-75% A + T residues), and all contain a particularly AT-rich 11 bp core element represented by the consensus sequence 5' (A/T)PuTT-TATTTA(A/T) 3'. Deletion mapping indicates that the consensus in all cases is in the vicinity of a functional ARS domain. However precise excision of the consensus by in vitro mutagenesis has little effect on ARS activity as judged by the transformation assay. We argue that the association of the consensus with the ARS domain occurs too reproducibly to be explained by chance alone. We suggest that although it may not be essential for the extrachromosomal maintenance of plasmids in S. pombe, the consensus does have a function in situ in the chromosome and thus is always present as a cryptic sequence in the isolated ARS element.

Absorption of 1.5% glycine after percutaneous ultrasonic lithotripsy for renal stone disease

An elderly normotensive man underwent percutaneous ultrasonic lithotripsy for renal stone disease, the procedure lasting three hours and the fragments being washed out with 20 l 1.5% glycine. After two hours the inflation pressure had risen to 25 cm H2O and his blood pressure to 150 mm Hg. Inflation pressure continued to rise until drainage tubes were inserted into the retroperitoneal space, releasing a large volume of fluid, some of which appeared to be from the peritoneal cavity. Shortly after transfer to the recovery area the patient showed signs of the transurethral resection syndrome, with hyponatraemia, hyperkalaemia, and hypertension. He was treated appropriately and survived. Low infusion pressures should be used for irrigation during lithotripsy and 0.9% saline instead of 1.5% glycine. In patients given a general anaesthetic any rise in inflation pressure suggests extravasation of fluid and warrants emergency estimation of the plasma sodium concentration.