High-throughput solution processing of large-scale graphene

The electronic properties of graphene, such as high charge carrier concentrations and mobilities, make it a promising candidate for next-generation nanoelectronic devices. In particular, electrons and holes can undergo ballistic transport on the sub-micrometre scale in graphene and do not suffer from the scale limitations of current MOSFET technologies. However, it is still difficult to produce single-layer samples of graphene and bulk processing has not yet been achieved, despite strenuous efforts to develop a scalable production method. Here, we report a versatile solution-based process for the large-scale production of single-layer chemically converted graphene over the entire area of a silicon/SiO(2) wafer. By dispersing graphite oxide paper in pure hydrazine we were able to remove oxygen functionalities and restore the planar geometry of the single sheets. The chemically converted graphene sheets that were produced have the largest area reported to date (up to 20 x 40 microm), making them far easier to process. Field-effect devices have been fabricated by conventional photolithography, displaying currents that are three orders of magnitude higher than previously reported for chemically produced graphene. The size of these sheets enables a wide range of characterization techniques, including optical microscopy, scanning electron microscopy and atomic force microscopy, to be performed on the same specimen.

Practical chemical sensors from chemically derived graphene

We report the development of useful chemical sensors from chemically converted graphene dispersions using spin coating to create single-layer films on interdigitated electrode arrays. Dispersions of graphene in anhydrous hydrazine are formed from graphite oxide. Preliminary results are presented on the detection of NO(2), NH(3), and 2,4-dinitrotoluene using this simple and scalable fabrication method for practical devices. Current versus voltage curves are linear and ohmic in all cases, studied independent of metal electrode or presence of analytes. The sensor response is consistent with a charge transfer mechanism between the analyte and graphene with a limited role of the electrical contacts. A micro hot plate sensor substrate is also used to monitor the temperature dependence of the response to nitrogen dioxide. The results are discussed in light of recent literature on carbon nanotube and graphene sensors.

Low-temperature solution processing of graphene-carbon nanotube hybrid materials for high-performance transparent conductors

We report the formation of a nanocomposite comprised of chemically converted graphene and carbon nanotubes. Our solution-based method does not require surfactants, thus preserving the intrinsic electronic and mechanical properties of both components, delivering 240 ohms/square at 86% transmittance. This low-temperature process is completely compatible with flexible substrates and does not require a sophisticated transfer process. We believe that this technology is inexpensive, is massively scalable, and does not suffer from several shortcomings of indium tin oxide. A proof-of-concept application in a polymer solar cell with power conversion efficiency of 0.85% is demonstrated. Preliminary experiments in chemical doping are presented and show that optimization of this material is not limited to improvements in layer morphology.

Escherichia coli: the best biological drinking water indicator for public health protection

Public health protection requires an indicator of fecal pollution. It is not necessary to analyse drinking water for all pathogens. Escherichia coli is found in all mammal faeces at concentrations of 10 log 9(-1), but it does not multiply appreciably in the environment. In the 1890s, it was chosen as the biological indicator of water treatment safety. Because of method deficiencies, E. coli surrogates such as the 'fecal coliform' and total coliforms tests were developed and became part of drinking water regulations. With the advent of the Defined Substrate Technology in the late 1980s, it became possible to analyse drinking water directly for E. coli (and, simultaneously, total coliforms) inexpensively and simply. Accordingly, E. coli was re-inserted in the drinking water regulations. E. coli survives in drinking water for between 4 and 12 weeks, depending on environmental conditions (temperature, microflora, etc.). Bacteria and viruses are approximately equally oxidant-sensitive, but parasites are less so. Under the conditions in distribution systems, E. coli will be much more long-lived. Therefore, under most circumstances it is possible to design a monitoring program that permits public health protection at a modest cost. Drinking water regulations currently require infrequent monitoring which may not adequately detect intermittent contamination events; however, it is cost-effective to markedly increase testing with E. coli to better protect the public's health. Comparison with other practical candidate fecal indicators shows that E. coli is far superior overall.

Sildenafil, a novel effective oral therapy for male erectile dysfunction

OBJECTIVES

To determine the efficacy and safety of sildenafil, a novel orally active inhibitor of the type-V cyclic guanosine monophosphate-specific phosphodiesterase (the predominant isoenzyme in the human corpus cavernosum) on penile erectile activity in patients with male erectile dysfunction of no established organic cause.

PATIENTS AND METHODS

Twelve patients (aged 36-63 years) with male erectile dysfunction of no established organic cause were entered into a double-blind, randomized, placebo-controlled, crossover study which was conducted in two phases. In the first phase (four-way crossover), treatment efficacy was evaluated by measurements of penile rigidity using penile plethysmography during visual sexual stimulation at different doses of sildenafil (10, 25 and 50 mg or placebo). In the second phase (two-way crossover), efficacy was assessed by a diary record of penile erectile activity after single daily doses of sildenafil (25 mg) or placebo for 7 days.

RESULTS

The mean (95% confidence interval, CI) duration of rigidity of > 80% at the base of the penis was 1.3 min (0.4-3.1) in patients on placebo, 3.5 min (1.6-7.3; P = 0.009) on 10 mg, 8.0 min (3.7-16.7; P = 0.003) on 25 mg and 11.2 min (5.6-22.3; P < 0.001) on 50 mg of sildenafil. The mean (95% CI) duration of rigidity of > 80% at the tip of the penis was 1.2 min (0.4-2.7) on placebo and 7.4 min (2.4-8.5; P = 0.001) on 50 mg sildenafil. From the diary record of daily erectile activity, the mean (95% CI) total number of erections was significantly higher in patients receiving sildenafil was 6.1 (3.2-11.4), compared with 1.3 (0.5-2.7) in those on placebo; 10 of 12 patients reported improved erectile activity while receiving sildenafil, compared with two of 12 on placebo (P = 0.018). Six patients on active treatment and five on placebo reported mild and transient adverse events which included headache, dyspepsia and pelvic musculo-skeletal pain.

CONCLUSION

These results show that sildenafil is a well tolerated and effective oral therapy for male erectile dysfunction with no established organic cause and may represent a new class of peripherally acting drug for the treatment of this condition.

Pharmacokinetics and safety of voriconazole following intravenous- to oral-dose escalation regimens

In this study, the safety, tolerability, and pharmacokinetics of intravenous (i.v.)- to oral-dose regimens of voriconazole were evaluated with a group of 42 healthy men, 41 of whom completed the study. Two cohorts of subjects participated in the study. Cohort 1 (n = 28) took part in two study periods, each consisting of 14 days separated by a minimum 7-day washout. In one of the periods, 14 subjects received 6 mg/kg i.v. twice a day (b.i.d.) on day 1 followed by 3 mg/kg i.v. b.i.d. on days 2 to 7 and were then switched to 200 mg orally b.i.d. for days 8 to 14. In the other period, subjects received 6 mg/kg i.v. b.i.d. on day 1 followed by 5 mg/kg i.v. b.i.d. on days 2 to 7 and were then switched to 400 mg orally b.i.d. for days 8 to 14. The remaining 14 subjects in cohort 1 received a matching placebo throughout the study. In cohort 2 (n = 14), 7 subjects received 6 mg/kg i.v. b.i.d. on day 1 followed by 4 mg/kg i.v. b.i.d. on days 2 to 7 and were then switched to 300 mg orally b.i.d. for days 8 to 14. The remaining seven subjects in cohort 2 received a matching placebo. Blood samples were taken prior to dosing on days 1 to 6 and on days 8 to 13. Blood samples were drawn prior to dosing and at frequent intervals up to 12 h following the morning dose on days 7 and 14 of each study period. The samples were assayed for voriconazole by a high-performance liquid chromatography method. The maximum concentration in plasma (C(max)) occurred at the end of the 1-h i.v. infusion and between 1.4 and 1.8 h after oral administration. Voriconazole exhibited nonlinear pharmacokinetics, possibly due to saturable metabolism. For cohort 1, both C(max) and the area under the concentration-time curve within a dosage interval (AUC(tau)) increased disproportionately with dose for both i.v. and oral dosing. For i.v. dosing, a 1.7-fold increase in dose resulted in 2.4- and 3.1-fold increases in C(max) and AUC(tau), respectively. Similarly, a 2-fold increase in oral dosing resulted in 2.8- and 3.9-fold increases in C(max) and AUC(tau), respectively. The mean values for C(max) observed following oral dosing were lower than those obtained after i.v. administration, ranging from 62.7 to 89.6% of the i.v. value. After the switch from i.v. to oral dosing, most subjects achieved steady state by day 4, and mean minimum concentrations in plasma remained above clinically important MICs. The pharmacokinetic profiles for saliva followed a pattern similar to those observed for plasma; there was a highly significant correlation between plasma and saliva voriconazole concentrations (P < 0.0001). Voriconazole was well tolerated; the most commonly reported adverse events in voriconazole-treated subjects were mild to moderate headache, rash, and abnormal vision. Visual function tests detected no further abnormalities during voriconazole treatment.

Effects of sildenafil citrate on human hemodynamics

Nitric oxide (NO) induces the formation of intracellular cyclic guanosine monophosphate (cGMP) by guanylate cyclase. Sildenafil, which selectively inhibits phosphodiesterase type 5 (PDE5) found predominantly in the corpora cavernosa of the penis, effectively blocks the degradation of cGMP and enhances erectile function in men with erectile dysfunction. The NO-cGMP pathway also plays an important role in mediating blood pressure. It is, therefore, possible that the therapeutic doses of sildenafil used to treat erectile dysfunction may have clinically significant effects on human hemodynamics. Three studies were undertaken to assess the effects of intravenously, intra-arterially, and orally administered doses of sildenafil on blood pressure, heart rate, cardiac output, and forearm blood flow and venous compliance in healthy men. A fourth study evaluated the hemodynamic effects of intravenous sildenafil in men with stable ischemic heart disease. In healthy men, significant (p <0.01) decreases in supine systolic and diastolic blood pressures were observed with intravenous sildenafil (20, 40, and 80 mg) at the end of the infusion period when plasma levels of sildenafil were highest (mean decreases from baseline of 7.0/6.9 and 9.2/6.7 mm Hg, for the 40- and 80-mg doses, respectively). These changes were transient and not dose related. Modest reductions in systemic vascular resistance also were observed (maximum decrease 16%), although heart rate was not affected by sildenafil administration when compared with placebo. Single oral doses of sildenafil (100, 150, and 200 mg) produced no significant changes in cardiac index from 1-12 hours postdose between placebo- and sildenafil-treated subjects. The approved dosage strengths of sildenafil citrate are 25 mg, 50 mg, and 100 mg. The 80-mg intravenous dose and the 200-mg oral dose of sildenafil produced comparable plasma levels at twice the maximum therapeutic dose (recommended range, 25-100 mg). After brachial artery infusion of sildenafil (up to 300 microg/min), there was a modest vasodilation of resistance arteries and a reversal of norepinephrine-induced preconstriction of forearm veins. These hemodynamic effects were similar to but smaller in magnitude than those of nitrates. In a small pilot study of men with ischemic heart disease, decreases from baseline in pulmonary arterial pressure (-27% at rest and -19% during exercise) and cardiac output (-7% at rest and -11% during exercise) were observed after 40-mg intravenous doses of sildenafil. Sildenafil was well tolerated by subjects and patients in all studies, with headache and other symptoms of vasodilation the most commonly reported adverse effects of treatment. Modest, transient hemodynamic changes were observed in healthy men after single intravenous or oral doses of sildenafil even at supratherapeutic doses. In men with stable ischemic heart disease, sildenafil produced modest effects on hemodynamic parameters at rest and during exercise.

A human homolog of yeast pre-mRNA splicing gene, PRP31, underlies autosomal dominant retinitis pigmentosa on chromosome 19q13.4 (RP11)

We report mutations in a gene (PRPF31) homologous to Saccharomyces cerevisiae pre-mRNA splicing gene PRP31 in families with autosomal dominant retinitis pigmentosa linked to chromosome 19q13.4 (RP11; MIM 600138). A positional cloning approach supported by bioinformatics identified PRPF31 comprising 14 exons and encoding a protein of 499 amino acids. The level of sequence identity to the yeast PRP31 gene indicates that PRPF31 is also likely to be involved in pre-mRNA splicing. Mutations that include missense substitutions, deletions, and insertions have been identified in four RP11-linked families and three sporadic RP cases. The identification of mutations in a pre-mRNA splicing gene implicates defects in the splicing process as a novel mechanism of photoreceptor degeneration.

Sildenafil citrate and blood-pressure-lowering drugs: results of drug interaction studies with an organic nitrate and a calcium antagonist

Sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), is a well-tolerated and highly effective treatment for erectile dysfunction. The mechanism of action of sildenafil depends on activation of the nitric oxide (NO)-cGMP pathway during sexual stimulation, which results in corpus cavernosal smooth muscle relaxation and penile erection. Endogenously derived NO is also involved in blood pressure regulation through its effect on basal vascular tone, which is mediated by cGMP levels. Organic nitrates and NO donors exert their therapeutic effects on blood pressure and vascular smooth muscle by the same mechanism as endogenous NO. Since both sildenafil and organic nitrates exert their pharmacologic effects via increases in cGMP concentrations, a double-blind, placebo-controlled, crossover study was undertaken to investigate the effects of sildenafil coadministered with glyceryl trinitrate on blood pressure and heart rate in healthy male subjects. The hemodynamic effects of sildenafil were also evaluated in a second placebo-controlled crossover study in men with hypertension who were taking the calcium antagonist amlodipine, which has a mechanism of action that does not involve the cGMP pathway. In the first crossover study, subjects were treated with oral sildenafil (25 mg, 3 times a day for 4 days) or placebo and then challenged on day 4 with a 40-minute, stepwise, intravenous infusion of glyceryl trinitrate (0.5 mg/mL in 5% dextrose at an initial infusion rate of 2.5 microg/min and doubling every 5 minutes to a maximum rate of 40 microg/min) 1 hour after taking sildenafil or placebo. On day 5, subjects received a sublingual glyceryl trinitrate tablet (500 microg) 1 hour after taking 25 mg of sildenafil or placebo. During sildenafil treatment, the subjects were significantly less tolerant of intravenously administered glyceryl trinitrate than during placebo treatment, based on the occurrence of a >25 mm Hg decrease in blood pressure or the incidence of symptomatic hypotension (p <0.01). When a sublingual glyceryl trinitrate tablet was administered on day 5, a 4-fold greater decrease in systolic blood pressure was observed for the subjects during the sildenafil treatment period than during the placebo treatment period. The changes in heart rate were negligible during both glyceryl trinitrate challenges. In conclusion, sildenafil potentiated the hypotensive effects of glyceryl trinitrate, an organic nitrate. Thus, sildenafil administration to patients who are using organic nitrates, either regularly and/or intermittently, in any form is contraindicated. In the second crossover study, men with hypertension, who were taking 5 or 10 mg/day of amlodipine, received a single oral dose of 100 mg sildenafil or placebo. Coadministration of sildenafil did not significantly affect the pharmacokinetics of amlodipine. In the 4 hours after dosing, differences in the mean maximum change from baseline in supine systolic and diastolic blood pressures between the sildenafil plus amlodipine and the placebo plus amlodipine treatment periods were -8 mm Hg and -7 mm Hg, respectively (p < or =0.002). The mean maximum supine heart rate increased 2.1 beats/min during sildenafil plus amlodipine treatment and decreased 1.5 beats/min during placebo plus amlodipine treatment (p <0.02). The adverse events in this study were predominantly mild or moderate and did not cause discontinuation of treatment. Adverse events considered to be related to sildenafil treatment included headache, nausea, and dyspepsia. In patients with hypertension who were taking amlodipine therapy, sildenafil produced additive, but not synergistic, reductions in blood pressure. The difference in the mean maximum change from baseline in blood pressure between sildenafil plus amlodipine and placebo plus amlodipine was comparable to the decrease in blood pressure reported for healthy men taking sildenafil alone. (ABSTRACT TRUNCATED)

Properties of biomolecules measured from atomic force microscope images: a review

AFM images can be used to obtain quantitative or qualitative information about the properties of biomaterials. Examples presented here are: (1) Persistence length measurements of moving and stationary DNA molecules. (2) Force mapping to measure properties such as the elasticity of cells and vesicles. (3) Phase mode imaging to detect variations in materials and properties of the sample surface. (4) Imaging of surfaces at different constant forces.

Baseline quality of life predicts survival in patients with advanced colorectal cancer

The aim of this study was to investigate the influence of baseline quality of life (QoL) on survival in patients with advanced colorectal cancer. From 1992 to 1998, four randomised clinical trials in advanced colorectal cancer were conducted at this institution. The European Organization for Research and Treatment of Cancer-Quality of Life Core 30 (EORTC-QLQ-C30) questionnaire was completed prior to the commencement of chemotherapy. Analyses were performed on median-dichotomised baseline Quality of Life (QoL) and clinical prognostic factors. Baseline QoL questionnaires were completed by 501 patients. One-year survival was 38.3 and 72.5% (P<0.0001) for patients with global QoL scores below and above the median (67), respectively. Other than cognitive functioning, fatigue, appetite, constipation, diarrhoea and financial domains, all QoL scales were significant independent predictors of survival (P<0.035). In the final model, the global QoL score remained highly significant as an independent predictor of survival (P<0.0001). Baseline QoL is a strong independent predictor of survival in patients with advanced colorectal cancer. Measurements should be routinely recorded in clinical trials to stratify cohorts and aid in trial comparison.

Pro-inflammatory cytokines and the pathogenesis of Gaucher's disease: increased release of interleukin-6 and interleukin-10

Gaucher's disease is characterized by hepatosplenomegaly, bone-marrow infiltration, osteonecrosis and bone thinning, associated with the presence of pathological macrophages that contain undegraded glycosphingolipids. To investigate the possible role of cytokines in the systemic and local manifestations of established Gaucher's disease, interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF alpha) and interleukin-10 (IL-10) were measured in freshly-separated serum. Samples from eight male and 14 female patients with type 1 Gaucher's disease were compared with sera from 22 healthy age- and sex-matched controls. Concentrations of IL-6 and IL-10 were significantly elevated in sera from patients with Gaucher's disease (11.9 +/- 1.8 (SEM) pg/ml and 5.4 +/- 0.5 (SEM) pg/ml, respectively) compared with those of controls (4.1 +/- 0.9 (SEM) and 0.8 +/- 0.3 (SEM) pg/ml, p < 0.0001). No significant differences in concentrations of TNF alpha or IL-1 beta were identified. IL-6 has been implicated in the development of localized osteolysis in multiple myeloma and in the development of post-menopausal osteoporosis. High concentrations of IL-6 in the serum of patients with Gaucher's disease may thus reflect the development of the bone lesions commonly associated with this disorder. Since IL-6 and IL-10 are important regulators of lymphocyte growth and differentiation, and IL-6 concentrations were significantly raised in patients with oligo- or polyclonal increases in serum immunoglobulins, enhanced release of these cytokines from pathological macrophages provides a pathological link between Gaucher's disease and associated lympho-proliferative disorders.

Identification of the skeletal remains of Josef Mengele by DNA analysis

There has been considerable controversy over the identity of the skeletal remains exhumed in Brazil in 1985 and believed to be those of Dr Josef Mengele, the Auschwitz 'Angel of Death'. Bone DNA analysis was therefore conducted in an attempt to provide independent evidence of identity. Trace amounts of highly degraded human DNA were successfully extracted from the shaft of the femur. Despite the presence of a potent inhibitor of DNA amplification, microsatellite alleles could be reproducibly amplified from the femur DNA. Comparison of the femur DNA with DNA from Josef Mengele's son and wife revealed a bone genotype across 10 different loci fully compatible with paternity of Mengele's son. Less than 1 in 1800 Caucasian individuals unrelated to Mengele's son would by chance show full paternal inclusion. DNA analysis therefore provides very strong independent evidence that the remains exhumed from Brazil are indeed those of Josef Mengele.

Peritoneovenous shunting as compared with medical treatment in patients with alcoholic cirrhosis and massive ascites. Veterans Administration Cooperative Study on Treatment of Alcoholic Cirrhosis with Ascites

The optimal management of severe ascites in patients with alcoholic cirrhosis has not been defined. in a 5 1/2-year study, we randomly assigned 299 men with alcoholic cirrhosis, who had persistent or recurrent severe ascites despite a standard medical regimen, to receive either intensive medical treatment or peritoneovenous (LeVeen) shunting. We identified three risk groups: Group 1 had normal or mildly abnormal results on liver-function tests, Group 2 had more severe liver dysfunction or previous complications, and Group 3 had severe prerenal azotemia without kidney disease. For the patients who received the medical treatment and those who received the surgical treatment combined, the median survival times were 1093 days in Group 1, 222 days in Group 2, and 37 days in Group 3 (P less than or equal to 0.01) for all comparisons). For all the groups combined, the median time to the resolution of ascites was 5.4 weeks for medical patients and 3.0 weeks for surgical patients (P less than 0.01). Within each risk group, mortality during the initial hospitalization and median long-term survival were similar among patients receiving either treatment. However, the median time to the recurrence of ascites in Group 1 was 4 months in medical patients, as compared with 18 months in surgical patients (P = 0.01); in Group 2 it was 3 months in medical patients as compared with 12 months in surgical patients (P = 0.04). The median duration of hospitalization was longer in medical patients than in surgical patients (6.1 vs. 2.4 weeks in Group 1 [P less than 0.001] and 5.0 vs. 3.1 weeks in Group 2 [P less than 0.01]). Group 3 was too small to permit a meaningful comparison. During the initial hospitalization, the incidence of infections, gastrointestinal bleeding, and encephalopathy was similar among the medical and surgical patients. We conclude that peritoneovenous shunting alleviated disabling ascites more rapidly than medical management. However, survival was closely related to the severity of the illness at the time of randomization and was not altered by shunting.

Bone turnover mediates preferential localization of prostate cancer in the skeleton

Bone metastasis is a common untreatable complication associated with prostate cancer. Metastatic cells seed in skeletal sites under active turnover containing dense marrow cellularity. We hypothesized that differences in these skeletal-specific processes are among the critical factors that facilitate the preferential localization of metastatic prostate cancer in bone. To test this, athymic mice were administered PTH to induce bone turnover and increase marrow cellularity daily 1 wk before and after intracardiac inoculation of luciferase-tagged PC-3 cells. Tumor localization was monitored by bioluminescence imaging weekly for 5 wk. At the time of tumor inoculation, PTH-treated mice demonstrated significant increases in serum levels of bone turnover markers such as osteocalcin and tartrate-resistant acid phosphatase 5b and in the number of tartrate-resistant acid phosphatase-positive osteoclasts per millimeter of bone when compared with the other groups. Likewise, PTH treatment stimulated a qualitative increase in marrow cellular proliferation as determined by 5-bromo-2'-deoxyuridine immunostaining. Skeletal metastases formed in the hind limb and craniofacial regions of young mice with no difference between groups. In adult mice, however, bioluminescent signals in the hind limb and craniofacial regions were 3-fold higher in PTH-treated mice vs. controls. Fluorochrome labeling revealed increased bone formation activity in trabecular bone adjacent to tumors. When zoledronic acid, a nitrogen-containing bisphosphonate that inhibits osteoclast-mediated bone resorption, was administered concurrently with PTH, a significant reduction in the incidence of bone tumors was observed. Overall, these studies provide new evidence that skeletal sites rich in marrow cellularity under active turnover offer a more congenial microenvironment to facilitate cancer localization in the skeleton.

Well-defined genome architecture in the human sperm nucleus

Using fluorescence in situ hybridization, conventional epifluorescence microscopy, and laser scanning confocal microscopy followed by three-dimensional reconstruction we describe a well-defined higher order packaging of the human genome in the sperm cell nucleus. This was determined by the spatial localization of centromere and telomere regions of all chromosomes and supported by localization of subtelomere sequences of chromosome 3 and the entire chromosome 2. The nuclear architecture in the human sperm is characterized by the clustering of the 23 centromeres into a compact chromocenter positioned well inside the nucleus. The ends of the chromosomes are exposed to the nuclear periphery where both the subtelomere and the telomere sequences of the chromosome arms are joined into dimers. Thus chromosomes in the human sperm nucleus are looped into a hairpin-like configuration. The biological implications of this nuclear architecture in spermatogenesis and male pronuclear formation following fertilization are discussed.

Identification of the elemental packing unit of DNA in mammalian sperm cells by atomic force microscopy

DNA is packaged within the sperm cell nuclei of many vertebrates and all mammals in a highly condensed state by small basic proteins (protamines). Despite continuous investigation for nearly half a century, the actual packing arrangement of the DNA has remained unresolved. Atomic force and electron microscopy studies described in this report provide evidence that the fundamental packing unit for sperm DNA is a toroidal structure, 900A in outside diameter with a 150A diameter hole, which contains up to 60kb of DNA. Although the results presented here are based primarily upon investigations of mammalian sperm cells, they are expected to be valid for all sperm cells which utilize protamines to package DNA.

Conservative management of finger tip injuries in adults

A prospective trial was undertaken on fifty consecutive patients with a total of sixty finger tip injuries treated by conservative means at the Leicester Royal Infirmary Accident and Emergency Department. The injuries have been classified into groups and results reviewed after a period of one year.

AFM analysis of DNA-protamine complexes bound to mica

A novel method for reconstituting sperm chromatin was used to investigate how protamine 1 condenses DNA. Complexes formed in vitro using linearized plasmid DNA were imaged and measured by atomic force microscopy (AFM). The structures formed were found to be highly dependent on the sample preparation method used for reconstitution. Interstrand, side-by-side fasiculation of DNA and toroidal-like structures only 1-2 DNA diameters thick were observed for complexes formed in solution following direct mixing of the DNA and protamine. Large chromatin aggregates were also observed on the mica. However, if the DNA was first allowed to attach to the mica prior to addition of the protamine, well-defined toroidal complexes were formed without any observed DNA fasiculation or aggregate formation. The diameter of the toroids measured 30.6-50.2 nm (mean 39.4 nm). The dimensions of these structures indicate that the condensed DNA is stacked vertically by four to five turns, with each coil containing as little as 360-370 bp of 'B'-form DNA. This approach for preparing and imaging DNA-protamine complexes permits the analysis of intermediate structures 'trapped' on the mica as partially formed toruses of nucleoprotamine.

Contrast agents for MRI: 30+ years and where are we going?

Thirty years ago, Schering filed the first patent application for a contrast agent for magnetic resonance imaging (MRI) covering the forefather of the gadolinium contrast agents and still the most widely used gadolinium probe: gadolinium(III) diethylenetriaminepentaacetate (Magnevist). To date, 11 contrast agents have been approved by the US Food and Drug Administration for intravenous use. Coordination chemists have done a great deal to move the field forward. Our understanding of lanthanide chemistry now makes possible the design of complexes with long rotational correlation times, fast or slow water-exchange rates, high thermodynamic stabilities, and kinetic inertness, leading to sensitive and nontoxic contrast agents. Chemists did not stop there. The last few decades has seen the development of novel classes of probes that yield contrast through different mechanisms, such as paramagnetic chemical exchange saturation transfer agents. Thirty years since the first patent, chemists are still leading the way. The development of high-sensitivity contrast agents for high magnetic fields, safe probes for patients with kidney disorders, and multimodal, targeted, and responsive agents demonstrates that the field of contrast agents for MRI still has much to offer.

'Whiplash injuries' of the neck: a retrospective study

This is a retrospective study of 102 patients with whiplash injuries of the neck followed up at approximately 2 years. The results show that 67 patients were asymptomatic by this time and the remaining 35 patients still exhibited symptoms. Prognostic indicators were found to be age, occipital headaches, referred symptoms, interscapular pain, abnormal neurological signs, positive radiological findings and osteoarthritic changes of the cervical spine. Symptoms that persisted for more than 2 months indicated prolonged disability.