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Biomedical subjects

T Allen

Publications and source records attributed to T Allen.

At least 37 records · Page 2Linked to original sources

Cutaneously applied acyclovir acts systemically in the treatment of herpetic infection in the hairless mouse.

Using the SKH-1 hairless mouse (HM) we have addressed the issue as to whether topically applied acyclovir (ACV) may mediate some of its antiviral actions by a systemic effect. When topically applied in a formulation consisting of polyvinyl alcohol (25% w/v):DMSO:cremophor EL:linoleic acid (63:16:16:5, v/v/v/v), ACV penetrated hairless mouse skin in a concentration-dependent manner and dose-dependently reduced cutaneous herpes simplex virus 1 (HSV-1) KOS infection. Topically applied ACV also effectively reduced the mortality associated with disseminated HSV-2 HG-52 infection. At 1 h following topical application of 1.7% w/v ACV the plasma and skin concentrations of ACV were 5.5 nmoles/ml and 120 nmoles/g. At 1 h following an oral dose of ACV with antiviral efficacy comparable to topically applied ACV (1.7% w/v) the plasma and skin concentrations of ACV were 21.3 nmoles/ml and 51 nmoles/g. These findings imply that when applied topically to the HM, ACV can mediate a portion of its antiviral activity through a systemic mode of action.

Acyclovir↗

Initiating thrombolytic therapy for acute myocardial infarction: whose job is it anyway?

Although thrombolytic therapy has clearly become the standard of care for acute myocardial infarction (AMI), its delivery in Canada continues to be extremely variable. Significant unnecessary delays in the initiation of this treatment still occur in many hospitals and constitute the most common avoidable cause of death in patients with AMI. The authors agree with the statement by representatives of the member organizations of the Emergency Cardiac Care Coalition (see pages 483 to 487 of this issue) that emergency service providers must get patients to hospital sooner and that all eligible patients should receive thrombolytic therapy within 30 minutes of their arrival at hospital. This objective requires that thrombolytic therapy be initiated by emergency physicians and be supported by well-established guidelines for its use.

Emergency Service, Hospital↗

Use of the complete genome sequence information of Haemophilus influenzae strain Rd to investigate lipopolysaccharide biosynthesis.

The availability of the complete 1.83-megabase-pair sequence of the Haemophilus influenzae strain Rd genome has facilitated significant progress in investigating the biology of H.influenzae lipopolysaccharide (LPS), a major virulence determinant of this human pathogen. By searching the H. influenzae genomic database, with sequences of known LPS biosynthetic genes from other organisms, we identified and then cloned 25 candidate LPS genes. Construction of mutant strains and characterization of the LPS by reactivity with monoclonal antibodies, PAGE fractionation patterns and electrospray mass spectrometry comparative analysis have confirmed a potential role in LPS biosynthesis for the majority of these candidate genes. Virulence studies in the infant rat have allowed us to estimate the minimal LPS structure required for intravascular dissemination. This study is one of the first to demonstrate the rapidity, economy and completeness with which novel biological information can be accessed once the complete genome sequence of an organism is available.

Animals↗

Identification and characterization of murine gammaherpesvirus 68 gp150: a virion membrane glycoprotein.

Murine gammaherpesvirus 68 (MHV-68) is a naturally occurring virus of murid rodents which displays pathobiological characteristics similar to those of other gammaherpesviruses, including Epstein-Barr virus (EBV). However, unlike EBV and many other gammaherpesviruses, MHV-68 replicates in epithelial cells in vitro and infects laboratory strains of mice and therefore provides a good model for the study of gammaherpesviruses. Studies of sequences around the center of the MHV-68 genome identified a gene (designated BPRF1 for BamHI P fragment rightward open reading frame 1) whose putative product had motifs reminiscent of a transmembrane glycoprotein. All other gammaherpesviruses have a glycoprotein in this genomic position, but the BPRF1 gene showed sequence homology with only the EBV membrane antigen gp340/220. Biochemical analysis showed that the product of BPRF1 was a glycoprotein present on the surface of infected cells, and immunoelectron microscopy showed that it was present in the virus particle. In addition, antibodies to the BPRF1 product raised by using a bacterial fusion protein neutralized the virus in the absence of complement. The predominant molecular weights of the protein were 150,000 and 130,000. Pulse-chase analysis and endoglycosidase-H digestion showed that the 130,000-molecular-weight form was a precursor of the 150,000-molecular-weight form, and cell surface labelling showed that the 150,000-molecular-weight form alone was on the cell surface. We therefore named the protein gp150. Since gp150 is the first virion-associated glycoprotein and neutralizing determinant of MHV-68 to be characterized, it provides a valuable tool for the future study of virus-host interactions.

Amino Acid Sequence↗

Generation of a transcription map at the HSD17B locus centromeric to BRCA1 at 17q21.

A detailed transcription map of the 320-kb region containing the HSD17B locus on chromosome 17 was generated. Thirty unique cDNA fragments, retrieved following the hybridization of immobilized YACs to primary pools of cDNAs prepared from RNA of mammary gland, ovary, placenta, and the Caco-2 cell line, were aligned into 10 transcription units by physical mapping and hybridization to RNAs of a series of tissues. The cDNAs were then further characterized by sequencing and used to screen mammary gland cDNA libraries. Fragments corresponding to the broadly expressed gamma-tubulin and Ki antigen genes were identified. A full-length cDNA clone encoding a 117-amino-acid protein homologous to the rat ribosomal protein L34 was isolated. Portions of genes with restricted patterns of expression were also obtained, including the previously characterized HSD17B1. One new gene, for which a full-length cDNA was isolated, was found to have an interesting tissue-specific pattern of expression with abundant mRNA in both the colon and the testis and in the mammary carcinoma cell line BT-474. This contrasted with the barely detectable level observed in several tissues including normal mammary gland. Of the five additional transcription units identified, one showed no similarity, two showed identity to human expressed sequences, and two displayed similarity to genes of animal species by amino acid alignment. These latter cDNA clones include potential homologues of a rat nuclear tyrosine phosphatase and of a factor of Drosophila that is known to be involved in the negative regulation of transcription of segment identity genes.

Amino Acid Sequence↗

Synthesis and evaluation of 6,11-ethanohexahydrobenzo[b]quinolizidines: a new class of noncompetitive N-methyl-D-aspartate antagonists.

The synthesis and in vitro and in vivo evaluation of 12,13-cycloalkyl-6,11-ethanobenzo[b]-quinolizidines, a new class of noncompetitive N-methyl-D-aspartate (NMDA) antagonists acting at the PCP site on the NMDA receptor complex, is reported. Structure-activity relationship studies led to the identification of 10-hydroxy-(6 alpha,11 alpha,11 alpha beta,12R*,13S*)-1,3,4,6,11,11a,13,14,15,16-decahydro-12H- 6,11[1',2']-endo-cyclopenta-2H-pyrido[1,2-b]isoquinoline hydrobromide (5h) and 9-hydroxy-(6 alpha,11 alpha,11a beta,12R*,13S*)- 1,3,4,6,11,11a,13,14,15,16-decahydro-12H-6,11-[1',2']-endo-cycl ope nta-2H- pyrido[1,2-b]isoquinoline hydrobromide (5i), the most potent members of this series with Ki values of 2.3 +/- 0.2 and 2.3 +/- 0.5 nM, respectively. Molecular modeling studies revealed that this series of compounds occupies both lipophilic sites of the Andrews PCP receptor model and shares structural features which are common to other classes of known noncompetitive NMDA antagonists such as MK-801.

Animals↗

Developing key-feature problems and examinations to assess clinical decision-making skills.

This article introduces the concept of a key feature and describes its function as the cornerstone of key-feature problems, a new problem format for the written assessment of clinical decision-making skills of medical trainees and practitioners. The rationale for using this problem format and the steps in problem and examination development--including issues of scoring and standard setting--are described. A key feature is defined as a critical step in the resolution of a clinical problem, and a key-feature problem consists of a clinical case scenario followed by questions that focus on only those critical steps. The questions can be presented to require examinees either to write in their responses or to select them from a list of options. For each question, examines can be instructed to supply or select whatever number of responses is appropriate to the clinical task being tested, and answer keys can comprise one or several responses. This problem format, with its focus on only the critical steps in problem resolution, and with its flexibility in question format and scoring keys, effectively addresses the psychometric considerations of content validity and test score reliability, and accommodates the complexity and configurations of actions often required in the resolution of clinical problems.

Clinical Competence↗

Xenopus lamin B3 has a direct role in the assembly of a replication competent nucleus: evidence from cell-free egg extracts.

Xenopus egg extracts which assemble replication competent nuclei in vitro were depleted of lamin B3 using monoclonal antibody L6 5D5 linked to paramagnetic beads. After depletion, the extracts were still capable of assembling nuclei around demembranated sperm heads. Using field emission in lens scanning electron microscopy (FEISEM) we show that most nuclei assembled in lamin B3-depleted extracts have continuous nuclear envelopes and well formed nuclear pores. However, several consistent differences were observed. Most nuclei were small and only attained diameters which were half the size of controls. In a small number of nuclei, nuclear pore baskets, normally present on the inner aspect of the nuclear envelope, appeared on its outer surface. Finally, the assembly of nuclear pores was slower in lamin B3-depleted extracts, indicating a slower overall rate of nuclear envelope assembly. The results of FEISEM were confirmed using conventional TEM thin sections, where again the majority of nuclei assembled in lamin B3-depleted extracts had well formed double unit membranes containing a high density of nuclear pores. Since nuclear envelope assembly was mostly normal but slow in these nuclei, the lamin content of 'depleted' extracts was investigated. While lamin B3 was recovered efficiently from cytosolic and membrane fractions by our procedure, a second minor lamin isoform, which has characteristics similar to those of the somatic lamin B2, remained in the extract. Thus it is likely that this lamin is necessary for nuclear envelope assembly. However, while lamin B2 did not co-precipitate with lamin B3 during immunodepletion experiments, several protein species did specifically associate with lamin B3 on paramagnetic immunobeads. The major protein species associated with lamin B3 migrated with molecular masses of 102 kDa and 57 kDa, respectively, on one-dimensional polyacrylamide gels. On two-dimensional O'Farrell gels the mobility of the 102 kDa protein was identical to the mobility of a major nuclear matrix protein, indicating a specific association between lamin B3 and other nuclear matrix proteins. Nuclei assembled in lamin B3-depleted extracts did not assemble a lamina, judged by indirect immunofluorescence, and failed to initiate semi-conservative DNA replication. However, by reinoculating depleted extracts with purified lamin B3, nuclear lamina assembly and DNA replication could both be rescued. Thus it seems likely that the inability of lamin-depleted extracts to assemble a replication competent nucleus is a direct consequence of a failure to assemble a lamina.

Animals↗

Serious business.

Explore the source record for details and available documents.

Attitude of Health Personnel↗

Physician directed networks: the Renaissance perspective.

It is time for all providers, physicians, hospital executives and ancillary providers to find creative ways to meet the healthcare needs of their local communities. More efficient systems of health care delivery will come from noncompetitive partnerships based on shared visions, collaborations, openess, honesty and integrity. RHP can be a catalyst for physicians and other providers in the Kansas City area and throughout the state to respond to the challenges and opportunities that lie before them.

Community Health Services↗

Computer-assisted trauma care prototype.

Each year, civilian accidental injury results in 150,000 deaths and 400,000 permanent disabilities in the United States alone. The timely creation of and access to dynamically updated trauma patient information at the point of injury is critical to improving the state of care. Such information is often non-existent, incomplete, or inaccurate, resulting in less than adequate treatment by medics and the loss of precious time by medical personnel at the hospital or battalion aid station as they attempt to reassess and treat the patient. The Trauma Care Information Management System (TCIMS) is a prototype system for facilitating information flow and patient processing decisions in the difficult circumstances of civilian and military trauma care activities. The program is jointly supported by the United States Advanced Research Projects Agency (ARPA) and a consortium of universities, medical centers, and private companies. The authors' focus has been the human-computer interface for the system. We are attempting to make TCIMS powerful in the functions it delivers to its users in the field while also making it easy to understand and operate. To develop such a usable system, an approach known as user-centered design is being followed. Medical personnel themselves are collaborating with the authors in its needs analysis, design, and evaluation. Specifically, the prototype being demonstrated was designed through observation of actual civilian trauma care episodes, military trauma care exercises onboard a hospital ship, interviews with civilian and military trauma care providers, repeated evaluation of evolving prototypes by potential users, and study of the literature on trauma care and human factors engineering. This presentation at MedInfo '95 is still another avenue for soliciting guidance from medical information system experts and users. The outcome of this process is a system that provides the functions trauma care personnel desire in a manner that can be easily and accurately used in urban, rural, and military field settings. his demonstration will focus on the user interfaces for the hand-held computer device included in TCIMS, the Field Medic Associate (FMA). The FMA prototype is a ruggedized, water-resistant personal computer, weighing approximately 5 lbs. It has an LCD graphical user interface display for patient record input and output, pen-based and audio input, audio output, and wireless communications capabilities. Automatic recording and dynamic, graphical display of time-stamped trends in patient vital signs will be simulated during the demonstration. Means for accessing existing patient record information (e.g., allergies to particular medications) and updating the record with the nature of the injury, its cause, and the treatments that were administered will be shown. These will include use of an electronic pen to mark up anatoglyphs (standard drawings of human body appearing on computer screen) to show where injuries occurred and where treatments were applied, and to input textual descriptions of the nature of the injury, its cause, what treatments were administered, etc. Computer recognition of handwritten inputs will be shown. Likewise, voice annotation and audio playback of patient record information by medics and hospital personnel will be illustrated. These latter technologies free the care providers' hands to treat the patient; they can therefore provide inputs to the patient record while information is fresh in their minds. The audio playback option allows hospital personnel to select more detailed voice annotations of specific portions of the patient record by simply touching the electronic pen to a particular place where an electronic pen marking was made by a medic in the field and then listening to the medic's corresponding audio commentary. Finally, the FMA's means for assisting the medic in simultaneously managing several injured patients will be shown. (abstract truncated)

Emergency Medical Services↗

Basic fibroblast growth factor increases the multiplication and migration of a serum-free derivative of CACO-2 but does not affect differentiation.

Basic fibroblast growth factor (bFGF) is found in the extracellular matrix and around the endothelial and epithelial cells of some human colon carcinomas. It is believed to play a role in angiogenesis, but in addition, recent data suggest that it can directly stimulate mitogenesis in some colon carcinoma cell lines. To clarify the role of bFGF in human colon carcinoma, we developed a model of Caco-2 which grew in serum-free conditions so that the effect of bFGF on multiplication, migration, and differentiation could be studied in defined conditions. Through morphological and biochemical studies in serum-free conditions, we demonstrated that this subline of Caco-2 differentiated spontaneously on reaching confluence. Using this model, we found that bFGF did not affect differentiation but that multiplication and migration were increased. The implication of these findings is that bFGF, released from the extracellular matrix by invading cells or produced by neovascular endothelial cells, can increase the mitogenic rate and migratory potential of colon carcinoma cells. In addition, the dual role of bFGF in stimulating colon carcinoma cells directly and promoting angiogenesis suggests that anti-bFGF strategies could form the basis of a novel approach to the treatment of colon carcinoma.

Cell Differentiation↗

Physical mapping of the split hand/split foot locus on chromosome 7 and implication in syndromic ectrodactyly.

Split hand/split foot (ectrodactyly; SHSF) is a human developmental malformation characterized by missing digits and claw-like extremities. An autosomal dominant form of this disorder has been mapped to 7q21.3-q22.1; the locus has been designated SHFD1. We have constructed a physical map consisting of overlapping yeast artificial chromosome clones for the entire region. Somatic cell hybrid and fluorescent in situ hybridization analyses were used to define SHSF-associated chromosomal rearrangements in twelve patients. An SHFD1 critical interval of 1.5 Mb was established by analysis of five patients with deletions. Translocation or inversion breakpoints found in six patients were mapped within 700 kb of each other in the critical region. Of note is that eight of the patients analyzed (67%) are in fact classified as having syndromic ectrodactyly. Thus, these mapping data establish a relationship between simple split hand/split foot and this more complex group of human birth defects. Finally, we have mapped DLX5, a member of the Distal-less homeobox gene family, to the SHFD1 critical interval.

Abnormalities, Multiple↗