A 1 MA, variable risetime pulse generator for high energy density plasma research

COBRA is a 0.5 Omega pulse generator driving loads of order 10 nH inductance to >1 MA current. The design is based on independently timed, laser-triggered switching of four water pulse-forming lines whose outputs are added in parallel to drive the load current pulse. The detailed design and operation of the switching to give a wide variety of current pulse shapes and rise times from 95 to 230 ns is described. The design and operation of a simple inductive load voltage monitor are described which allows good accounting of load impedance and energy dissipation. A method of eliminating gas bubbles on the underside of nearly horizontal insulator surfaces in water was required for reliable operation of COBRA; a novel and effective solution to this problem is described.

Melioidosis in imported non-human primates

In 1969, five cases of melioidosis in three separate outbreaks were diagnosed in nonhuman primates in the United States. In the first outbreak, two stump-tailed macaque monkeys (Macaca arctoides) developed signs of the disease approximately 6 months after purchase. A third animal, a chimpanzee (Pan troglodytes), probably acquired its infection from one of these monkeys. Two other unrelated cases involving a pig-tailed monkey (Macaca nemestrina) and a rhesus monkey (Macaca mulatta) were diagnosed. These monkeys had been imported 3 years and 6 months, respectively, prior to the recognized onset of their disease. These cases represent the first known occurrences of spontaneous melioidosis in nonhuman primates in the United States.

Thiolactomycin and related analogues as novel anti-mycobacterial agents targeting KasA and KasB condensing enzymes in Mycobacterium tuberculosis

Prevention efforts and control of tuberculosis are seriously hampered by the appearance of multidrug-resistant strains of Mycobacterium tuberculosis, dictating new approaches to the treatment of the disease. Thiolactomycin (TLM) is a unique thiolactone that has been shown to exhibit anti-mycobacterial activity by specifically inhibiting fatty acid and mycolic acid biosynthesis. In this study, we present evidence that TLM targets two beta-ketoacyl-acyl-carrier protein synthases, KasA and KasB, consistent with the fact that both enzymes belong to the fatty-acid synthase type II system involved in fatty acid and mycolic acid biosynthesis. Overexpression of KasA, KasB, and KasAB in Mycobacterium bovis BCG increased in vivo and in vitro resistance against TLM. In addition, a multidrug-resistant clinical isolate was also found to be highly sensitive to TLM, indicating promise in counteracting multidrug-resistant strains of M. tuberculosis. The design and synthesis of several TLM derivatives have led to compounds more potent both in vitro against fatty acid and mycolic acid biosynthesis and in vivo against M. tuberculosis. Finally, a three-dimensional structural model of KasA has also been generated to improve understanding of the catalytic site of mycobacterial Kas proteins and to provide a more rational approach to the design of new drugs.

Influenza diagnosis: from dark isolation into the molecular light. West of Scotland Respiratory Virus Study Group

OBJECTIVES

To compare the conventional virus isolation method for diagnosis of influenza infection with reverse-transcription polymerase chain reaction (RT-PCR) in prospectively collected nose and throat swabs from elderly patients during the winter influenza season. The use of a denaturing buffer as an alternative to viral transport medium (VTM) for submission of combined nose and throat swabs to the laboratory for PCR was then investigated in a second study.

METHODS

Virus was cultured in microtitre plates using two different cell lines and detected using monoclonal antibody staining. A multiplex, matrix gene PCR assay was optimized to increase the sensitivity and specificity of detection of influenza A (H3 and H1) and B nucleic acid.

RESULTS

The multiplex assay detected all viruses with equal sensitivity to individual assays. In a large, multicentre field study PCR detected twice as many influenza infections compared with virus isolation. No positive culture was missed. PCR has a rapid turn around time (< 36 h) vs. a minimum of 7 days for virus isolation. Greater sensitivity and specificity in the PCR were achieved using a 'hot-start' method. Although the numbers were small, the detection rate using PCR was greater for swabs submitted in denaturing buffer than in VTM.

CONCLUSIONS

PCR significantly increased the sensitivity and clinical utility of influenza A (H3 and H1) and B diagnosis. There were a number of advantages in using denaturing buffer for submission of samples, including high sensitivity, rapidity, ease of use and no requirement for the virus to be viable on arrival at the laboratory. Therefore, PCR is a rapid, sensitive and user-friendly alternative for influenza diagnosis. Virus isolation technology should be limited to referral centres for further epidemiological characterization.

Antimycobacterial activities of isoxyl and new derivatives through the inhibition of mycolic acid synthesis

Isoxyl (ISO), a thiourea (thiocarlide; 4, 4'-diisoamyloxythiocarbanilide), demonstrated potent activity against Mycobacterium tuberculosis H37Rv (MIC, 2.5 micrograms/ml), Mycobacterium bovis BCG (MIC, 0.5 microgram/ml), Mycobacterium avium (MIC, 2.0 microgram/ml), and Mycobacterium aurum A+ (MIC, 2.0 microgram/ml), resulting in complete inhibition of mycobacteria grown on solid media. Importantly, a panel of clinical isolates of M. tuberculosis from different geographical areas with various drug resistance patterns were all sensitive to ISO in the range of 1 to 10 microgram/ml. In a murine macrophage model, ISO exhibited bactericidal killing of viable intracellular M. tuberculosis in a dose-dependent manner (0.05 to 2.50 microgram/ml). The selective action of ISO on mycolic acid synthesis was studied through the use of [1, 2-14C]acetate labeling of M. tuberculosis H37Rv, M. bovis BCG, and M. aurum A+. At its MIC for M. tuberculosis, ISO inhibited the synthesis of both fatty acids and mycolic acids (alpha-mycolates by 91.6%, methoxymycolates by 94.3%, and ketomycolates by 91.1%); at its MIC in M. bovis BCG, ISO inhibited the synthesis of alpha-mycolates by 87.2% and that of ketomycolates by 88.5%; and the corresponding inhibitions for M. aurum A+ were 87.1% for alpha-mycolates, 87.2% for ketomycolates, and 86.5% for the wax-ester mycolates. A comparison with isoniazid (INH) and ethionamide (ETH) demonstrated marked similarity in action, i.e., inhibition of the synthesis of all kinds of mycolic acids. However, unlike INH and ETH, ISO also inhibited the synthesis of shorter-chain fatty acids. ISO showed no acute toxicity against primary macrophage cell cultures as demonstrated by diminution of redox activity. A homologous series of ISO derivatives were synthesized. Most derivatives were as effective or more effective than the parent compound in the agar proportion assay. Thus, these thioureas, like INH and ETH, specifically inhibit mycolic acid synthesis and show promise in counteracting a wide variety of drug-sensitive and -resistant strains of M. tuberculosis.

Novel C-2 substituted carbapenem derivatives. Part IV. Synthesis and biological activity of five membered heteroaromatic derivatives

The synthesis, antibacterial activity, and stability to human dehydropeptidase-1 (DHP-1) of a novel series of (5R,6S)-6-[(1R)-1-hydroxyethyl]-2-heterocyclylcarbapen-2-em-3-carb oxylates are described. Of the compounds investigated 1,5-disubstituted pyrazol-3-yl and 3-substituted isoxazol-5-yl derivatives have the best combination of antibacterial activity and stability to DHP-1. They are particularly active against community-acquired respiratory tract pathogens and have stabilities to DHP-1 superior to that of meropenem.

Novel C-2 substituted carbapenem derivatives. Part II. Synthesis and structure-activity relationships of isoxazolin-2-yl, isoxazolidin-2-yl and 2-pyrazolin-2-yl carbapenems generated using 1,3-dipolar cycloaddition chemistry

A series of carbapenems containing novel C-2 semisaturated heterocyclic substituents were synthesised by 1,3 dipolar cycloaddition reactions of nitrile oxides, nitrile imines and a nitrone to 2-vinylcarbapenem. The isoxazoline and isoxazolidine compounds showed potent antibacterial activity but moderate stability to human dehydropeptidase 1 (DHP-1). Stability to DHP-1 was improved by methyl substitution in the isoxazoline ring, but at the expense of antibacterial activity. The pyrazolines exhibited excellent stability to DHP-1, but reduced potency against Gram-negative organisms.

Occupational asthma caused by automated salmon processing

Within 3 months of the opening of a salmon-processing plant in the UK, some workers complained of symptoms suggestive of occupational asthma. A survey of all 291 employees identified 24 (8.2%) with occupational asthma. The employees worked near machines which generated respirable aerosols containing salmon-serum proteins. The IgE response to these proteins was associated with occupational asthma (p < 0.001), with increasing severity of symptoms (p < 0.001), and with working distance from the aerosol source (p = 0.037). The main factor which predisposed to IgE-antibody production and asthma was cigarette smoking (p < 0.001), whereas atopy and a previous allergic history did not. The affected employees were reallocated to a low-exposure worksite and factory ventilation was improved. Eleven showed significant clinical and pulmonary function improvement, and continued in employment. Thirteen who still had symptoms were advised to leave, thereafter becoming symptom-free, and regaining normal respiratory function. Early recognition of symptoms and prompt action to reduce aerosol exposure avoided the long-term reduction in pulmonary functions often associated with occupational asthma.

Transcranial Doppler ultrasound in commercial air divers: a field study including cases with right-to-left shunting

Many cases of decompression illness occur in divers using recommended decompression tables. Doppler ultrasound has been used for over 20 yr and has shown the presence of venous bubbles in asymptomatic divers working well within decompression limits. Previous studies have demonstrated an increased prevalence of patent foramen ovale in divers who have suffered neurologic decompression illness. It has been postulated that right-to-left shunting through a patent foramen ovale could allow arterialization of these bubbles, causing symptoms and signs of acute decompression illness and possibly chronic subclinical neurologic impairment. We set out to determine the incidence of bubbles in the cerebral circulation of commercial divers decompressing from air dives. Using transcranial Doppler ultrasound (TCD), the middle cerebral arteries of 17 divers were monitored after surfacing from depths ranging between 3 and 50 m. Peripheral contrast injection with simultaneous transthoracic echocardiography and TCD was used to screen for right-to-left shunting. Right-to-left shunting was detected in four divers by TCD (one at rest, two after a Valsalva maneuver, and one only after coughing); however, echocardiography was positive in only one of these subjects after a Valsalva maneuver (TCD was positive at rest in this subject). Seventy-three TCD recordings were performed in four settings: 41 after underwater decompression, 18 after surface decompression, 10 in the interval between surfacing and entering the decompression chamber, and 4 after a chamber dive. Twenty-three of these recordings were in four subjects with right-to-left shunting; no bubbles were detected in any of these recordings.(ABSTRACT TRUNCATED AT 250 WORDS)

Salmon farming: occupational health in a new rural industry

The medical hazards of salmon farming can be grouped into those related to marine safety, fish husbandry, fish-farm diving and disease treatments. The hostile water environment requires thermal protection and personal buoyancy aids as workers frequently fall in the water from boats or cages. Feedstuffs may generate respirable dust and attract rats, creating a risk of leptospirosis. Musculo-skeletal injuries are common from lifting nets. Fish-farm diving has particular risks which can be minimized. Organophosphorous pesticides are used to treat sea lice and employees require health surveillance. Fish immunization is required to reduce the incidence of Aeromonas salmonitica. Needlestick injuries when using oil-based vaccines are a serious hazard to employees. The occupational health problems of salmon farming are predictable and preventable with primary safety measures. This new industry is safer than land-based agriculture on current evidence.

Deviance in the practice of science

The author discusses misconduct in biomedical research in terms of research about deviance. The ancient mantle of the sacred was transferred in the late nineteenth and early twentieth century from religious institutions to the scientists and the universities that they came to dominate. Universities were engaged in the pursuit of truth; and when science came to dominate universities, they became the hallowed ground of science. Many younger scientists consider that theirs is professional work like any other, but the general public, journalists, and policymakers still consider that scientists who break the rules are guilty of heinous offenses (violations of a sacred trust). This explains in part the different reactions of scientists and the public to recent scandals involving medical researchers. One of the most important points about deviance among scientists is the need to distinguish between rules imposed on the actor and rules that the individual is personally committed to. As government funding has come to dominate biomedical research, scientists have become part of huge bureaucratic entities with values, policies, and views often at variance from those of the scientific community. Increasingly, scientists find conflict between the values and mores of their community and the rules and mores of the federal and university bureaucracies that control modern science. Scientists can come to feel that they can violate the bureaucrats' rules and still be highly principled because they do not violate the values of science. The danger is that, by a process of drift, they can come to violate increasingly important, even primary, values of science.(ABSTRACT TRUNCATED AT 250 WORDS)

Heliox treatment for spinal decompression sickness following air dives

Enforced delay in treatment of spinal decompression sickness following scuba diving can result in paraplegia. Poor response from initial recompression to 18 m presents the clinician with a difficult management problem. Theoretical objections have been raised to the use of He-O2 as treatment regimen. We report 3 cases that show He-O2 to be an excellent method of treatment in spinal decompression sickness after air diving.

Intramuscular diclofenac sodium as adjuvant therapy for type I decompression sickness: a case report

The residual pain of type I decompression sickness (limb bends) occurring despite recompression therapy is due to an acute inflammatory reaction in the soft tissue around the joint. This case history reports an excellent response in resolving residual pain by the use of an intramuscular injection of the nonsteroidal anti-inflammatory drug, diclofenac sodium. The theoretical reasons for this are discussed.

Chromosome aberrations in divers

The incidence of chromosome gain and loss and chromosomal aberrations has been measured in 48-h lymphocyte cultures of divers and control subjects as part of an overall research program to identify possible long-term health hazards associated with commercial diving. When the two diving groups, air divers (n = 77) and helium-oxygen divers (n = 76), are compared with two control groups, oil rig workers (n = 75) and nonoil industry controls (n = 52), 3.9% (6 out of 153) had an unusually high number of structural aberrations in a small portion of the dividing lymphocytes. Similar damage was not found in controls. The remaining 147 divers had a similar low incidence of chromosomal aberrations to the two control groups. The factors responsible for this phenomenon are not known, but several aspects of diving can effectively be ruled out. These are: direct effects of pressure, breathing mixture, radiographic exposure, and viral infection. The causative agent must be acting locally on lymphocytes after their last maturation division. Further studies are continuing on this topic in an effort to identify the causative factor or factors.