Bacteriophage therapy.

In 1917, bacteriophages were recognized as epizootic infections of bacteria and were almost immediately deployed for antibacterial therapy and prophylaxis. The early trials of bacteriophage therapy for infectious diseases were confounded, however, because the biological nature of bacteriophage was poorly understood. The early literature reviewed here indicates that there are good reasons to believe that phage therapy can be effective in some circumstances. The advent of antibiotics, together with the "Soviet taint" acquired by phage therapy in the postwar period, resulted in the absence of rigorous evaluations of phage therapy until very recently. Recent laboratory and animal studies, exploiting current understandings of phage biology, suggest that phages may be useful as antibacterial agents in certain conditions.

Structure to 1.9 A resolution of a complex with herpes simplex virus type-1 thymidine kinase of a novel, non-substrate inhibitor: X-ray crystallographic comparison with binding of aciclovir.

Treatment of herpes infections with nucleoside analogues requires as an initial step the activation of the compounds by thymidine kinase. As an aid to developing more effective chemotherapy, both for treatment of recurrent herpes infection and in gene therapy systems where thymidine kinase is expressed, two high-resolution X-ray structures of thymidine kinase have been compared: one with the relatively poor substrate aciclovir (Zovirax), the other with a synthetic inhibitor having an N2-substituted guanine. Both compounds have similar binding modes in spite of their size difference and apparently distinct ligand properties.

The Chinese Nail Murders: forensic medicine in Imperial China.

Robert van Gulik was a respected Dutch sinologist and author who first translated a collection of traditional Chinese detective stories into English and then created additional fictional stories based on the same characters and setting in the Tang dynasty. One of these stories, The Chinese Nail Murders, draws on van Gulik's professional interest in law and his knowledge of early Chinese works on forensic medicine. This novel develops a common theme in Chinese detective fiction, murder by a nail wound to the head. The difficulty in detection of this mode of violence posed a particular problem for the examining magistrate because postmortem examination was mostly limited to external observations. This essay compares the development of Chinese and Western forensic medicine in the context of the nail murder motif.

Hans Zinsser: a tale of two cultures.

Hans Zinsser, president of the Society of American Bacteriologists in 1926, was known as much for his literary and textbook writing as for his scientific contributions. He was a widely known scientist and person of letters. His early interests in poetry and other forms of literature were maintained and developed during his career as a microbiologist, and his most enduring legacy is based on his writing about microbiology for a general readership as well as his reflective and philosophical autobiography.

5-Substituted pyrimidines with a 1,5-anhydro-2, 3-dideoxy-D-arabino-hexitol moiety at N-1: synthesis, antiviral activity, conformational analysis, and interaction with viral thymidine kinase.

A new series of anhydrohexitol nucleosides are described. These compounds have a pyrimidine base moiety substituted in the 5-position with a chloro (1b), trifluoromethyl (1c), vinyl (1d), 2-thienyl (1e), ethynyl (1f) or propynyl (1g) substituent. The vinyl, propynyl, and, in particular, the 5-trifluoromethyl analogue showed potent activity against herpes simplex virus (HSV), 1c with a selectivity index of >16000 against HSV-1 and >1000 against HSV-2. Conformational analysis of anhydrohexitol nucleosides using computational methods indicates that these nucleosides occur in an equilibrium between the C1 and 1C form with a DeltaE of 5.9 kJ/mol. When the anhydrohexitol nucleoside is cocrystallized with the HSV-1 thymidine kinase it adopts a 1C conformation, which is opposite to the conformation found for the small molecule alone. The enzyme, apparently, induces a conformational change, and conformational flexibility of an anhydrohexitol nucleoside may be advantageous for recognition by viral enzymes.

Exploring the active site of herpes simplex virus type-1 thymidine kinase by X-ray crystallography of complexes with aciclovir and other ligands.

Antiherpes therapies are principally targeted at viral thymidine kinases and utilize nucleoside analogs, the triphosphates of which are inhibitors of viral DNA polymerase or result in toxic effects when incorporated into DNA. The most frequently used drug, aciclovir (Zovirax), is a relatively poor substrate for thymidine kinase and high-resolution structural information on drugs and other molecules binding to the target is therefore important for the design of novel and more potent chemotherapy, both in antiherpes treatment and in gene therapy systems where thymidine kinase is expressed. Here, we report for the first time the binary complexes of HSV-1 thymidine kinase (TK) with the drug molecules aciclovir and penciclovir, determined by X-ray crystallography at 2.37 A resolution. Moreover, from new data at 2.14 A resolution, the refined structure of the complex of TK with its substrate deoxythymidine (R = 0.209 for 96% of all data) now reveals much detail concerning substrate and solvent interactions with the enzyme. Structures of the complexes of TK with four halogen-containing substrate analogs have also been solved, to resolutions better than 2.4 A. The various TK inhibitors broadly fall into three groups which together probe the space of the enzyme active site in a manner that no one molecule does alone, so giving a composite picture of active site interactions that can be exploited in the design of novel compounds.

Identification of oxacillin-susceptible and oxacillin-resistant Staphylococcus aureus using commercial latex agglutination tests.

Four hundred thirteen Staphylococcus sp. were identified by Staphaurex, Staphaurex Plus, and BACTiStaph kits using tube coagulase as reference. Among 222 coagulase-positive isolates, 56 were oxacillin-resistant Staphylococcus aureus. All tests were accurate in distinguishing between coagulase-positive and -negative staphylococci with sensitivities and specificities > or = 97% and only nine discrepancies.

3'-Amino thymidine affinity matrix for the purification of herpes simplex virus thymidine kinase.

A simple procedure for preparation of an affinity resin with 3'-amino thymidine linked to the carboxyl residues on 6-amino-hexanoic agarose is described. We have used this column for a rapid and simple purification of the thymidine kinase encoded by the herpes simplex virus type 1 genome. This resin has two major advantages over the most widely use used resin made with thymidine-p-nitrophenyl phosphate: first it is easily obtainable, and second, it is not subject to destruction by phosphodiesterases. The two resins are very similar in behavior and the resin made with amino thymidine has allowed us to prepare large quantities of highly purified HSV TK for crystallization studies.

Crystal structures of the thymidine kinase from herpes simplex virus type-1 in complex with deoxythymidine and ganciclovir.

The crystal structures of thymidine kinase from herpes simplex virus type-1 complexed with its natural substrate deoxythymidine (dT) and complexed with the guanosine analogue Ganciclovir have been solved. Both structures are in the C222(1) crystal form with two molecules per asymmetric unit related by a non-crystallographic two-fold axis. The present models have been refined to 2.8 A and 2.2 A, with crystallographic R factors of 24.1% and 23.3% for the dT and Ganciclovir complexes respectively, without the inclusion of any solvent molecules. The core of the molecule exhibits high structural homology with adenylate kinase and other nucleotide binding proteins. These structural similarities provide an insight into the mechanism of nucleoside phosphorylation by thymidine kinase.

Substrate specificity of Epstein-Barr virus thymidine kinase.

Purified recombinant protein encoded by the BXLF-I open reading frame of the Epstein-Barr virus genome has thymidine kinase activity. The substrate behaviors of various nucleosides toward this enzyme were tested. Halogenated deoxyuridines, zidovudine, and bromovinyldeoxyuridine are efficient substrates, while acyclovir and dihydroxypropylmethylguanine are relatively poor substrates for the Epstein-Barr virus thymidine kinase.

Congruences in Chinese and Western medicine from 1830-1911: smallpox, plague and cholera.

A close examination of three examples, smallpox, plague and cholera, suggest that for acute infectious diseases the Chinese viewed the symptomatologies, the causes, and the rational treatments of these illnesses in many ways similar to that of their contemporary Western counterparts. Rather than holding an opposing, clashing or incongruent system of medical thoughts for these common, well-recognized infectious diseases, the Chinese were prepared, by a long tradition of ontological thinking, to be receptive to the adoption, incorporation or modification of Western medical ideas in the late nineteenth century.

A method for selection of mutations at the tdk locus in Escherichia coli.

Mutants of Escherichia coli which are resistant to 5-fluorodeoxyuridine all have mutations which map at a single locus at 27.5 min on the genetic map of E. coli. Extracts prepared from each mutant were deficient in thymidine kinase activity measured in vitro. Simple selective conditions which allowed detection of one mutant in the presence of 10(7) wild-type bacteria were found. These results show that loss of thymidine kinase activity is the usual mechanism for 5-fluorodeoxyuridine resistance and that all such mutations occur at the locus previously designated tdk.

Chemiluminescent restriction fragment length polymorphism analysis (DNA fingerprinting) to identify keratinocytes from two donors in co-culture.

The transplantation of allogeneic cells such as pancreatic islet cells, bone marrow, and keratinocytes for skin replacement is in growing use clinically. Present techniques which are used to distinguish transplanted allogeneic cells from phenotypically identical host cells in chimeric tissue have serious limitations. This study assesses the feasibility of using chemiluminescent restriction fragment length polymorphism (RFLP) analysis to distinguish between keratinocyte cell lines from 2 different donors grown in co-culture. We evaluated the sensitivity of this technique in tissue cultured cells in order to define its usefulness in clinical situations. RFLP analysis readily detects heterologous DNA comprising only 10% of a 5 micrograms sample. This was a detection threshold of 500 ng of high molecular weight DNA. With standard extraction methods, this represents the DNA obtained from 4000 cells. This new chemiluminescent technique is as sensitive as older techniques which employ radioactive probes, but avoids the hazards of handling radioactive material. Using this RFLP analysis, the presence of transplanted allogeneic cells can be readily detected in small biopsy specimens. This technique has wide potential application in allogeneic cellular transplantation investigations.

Identification of the 12-O-tetradecanoylphorbol-13-acetate-responsive enhancer of the MS gene of the Epstein-Barr virus.

We previously located two 12-O-tetradecanoylphorbol-13-acetate (TPA)-responsive enhancers, MSTRE-I and MSTRE-II, in the upstream sequence of the MS gene of Epstein-Barr virus (Liu, Q., and Summers, W.C. (1989) J. Virol. 63, 5062-5068). The core sequence of the MSTRE-I enhancer is now determined to be between -718 and -708 of the upstream sequence of the MS gene. The activity of the enhancer is also sensitive to its immediate surrounding sequence on either side. A single copy of a 30-base pair (bp) fragment containing the MSTRE-I sequence was able to confer TPA responsiveness upon the MS promoter even in the absence of an AP-1 binding site. Multiple tandem copies of this 30-bp fragment, regardless of their relative orientations to each other, could function synergistically to enhance the MS promoter activity. At least two copies of the 30-bp fragment were required to bestow TPA induction upon the thymidine kinase gene promoter of herpes simplex virus type 1. The MSTRE-I sequence could also be bound by a Fos-GCN4 chimeric protein but with an affinity much lower than that between the chimeric protein and the AP-1 binding site. This MSTRE-I region has strong homology to one of the TPA-responsive elements (the ZII domain) in the upstream sequence of the EBV BZLF1 gene. In addition, a putative negative regulatory region or silencer was found immediately downstream of the MSTRE-I enhancer. This potential silencer region contains a 14-bp sequence that is homologous to the silencer consensus sequence of the BZLF1 gene. Therefore, the regulation of the MS gene may share the same pathway with the immediate early gene BZLF1.