Biomedical subjects
Publications and source records attributed to D I Smith.
An analysis of the number of persons killed and casualty accidents in the 3 years before and after the introduction of Sunday sales of alcoholic beverages in Perth, Western Australia, indicates that the new laws had a detrimental effect on traffic safety.
R938 carries a transposon (TAbeta) of approximate molecular weight 9.5 Megadaltons (Mdal, 10(6) daltons). This contains genes for a beta lactamase of type TEM-1 and for streptomycin phosphatransferase (SPT). There is a ten-fold difference in the efficiency of transposition in different strains of E. coli K12.
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We describe the isolation of a new class 2 restriction endonuclease from Providencia stuartii 164. Using the procedure of osmotic shock treatment, we have partially purified this enzyme (Pst 1) and have begun preliminary work to characterize its specificity and requirements. Pst 1 requires Mg++ as the only cofactor and produces more than 18 cleavages in wild type lambda. We have determined the location of 7 of these cleavages by the use of deletion and insertion mutants of lambda.
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R1033 is a plasmid of compatibility group P (= P1) transferred from a wild strain of Pseudomonas aeruginosa. It confers resistance to gentamicin by gentamicin acetyl-transferase 1 and to kanamycin and neomycin by neomycin phosphotransferase 1.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Simultaneous epidural and cortical depth recordings of the auditory middle latency response (MLR) were obtained from 18 anesthetized guinea pigs. Microelectrodes were advanced at a right angle to the cortical surface at sites shown to be optimal for recording surface MLRs. Transcortical polarity reversals of waves A (14 msec) and B (24 msec) of the MLR were recorded in depth penetrations initiated at sites on the temporal lobe with large amplitude surface potentials. In 6 of 18 penetrations yielding phase inversions, wave polarities changed abruptly as microelectrodes were advanced into the cortex. In the remaining penetrations, the reversals were preceded by gradual decreases in wave latencies at progressively deep sites. As electrodes were advanced beyond the depth at which polarity reversals were encountered, decreases in amplitude and only minor changes in latency were observed. Surface and depth MLR activity were temporarily eliminated immediately after electrolytic lesions were made at polarity reversal sites. Recovery of responses occurred within 30-60 min. Lesions produced in penetrations initiated at sites with no surface MLR activity had no effect. Histologic examination confirmed the location of the phase reversal sites as being within grey matter of the temporal lobe. These results are consistent with previous investigations in experimental animals which demonstrated transcortical polarity reversals, and provide evidence for dipolar generating systems of the early components of the MLR at the cortical level.
Surface preparations of the stria vascularis from guinea pigs exposed to wide-band noise or intoxicated with quinine monohydrochloride dihydrate were studied by light microscopy and computerized image analysis in order to evaluate quantitatively the effects of these agents on two characteristics of the strial vasculature: vascular density and erythrocyte distribution. An image analyzer was used to measure the area of strial vessel lumen and erythrocyte distribution as a fraction of the total area of strial tissue under observation. The results demonstrate that changes in the strial vessels do occur in guinea pigs exposed to noise or given large doses of quinine. Localized vessel narrowings caused by swollen endothelial cells and possibly by contraction of pericytes were found in both experimental groups, but there was no apparent tonotopical relationship between these effects and the reduction in cochlear potentials. A significant reduction in the number of erythrocytes was found in all turns of the cochlea in both experimental groups. Although a significant difference in vascular density was found among turns of the cochlea in both experimental and control animals, there was no widespread change in vascular density as a result of either noise exposure or quinine treatment.
Changes in threshold, latency, and amplitude of the auditory middle latency response (MLR) with anesthesia and neuromuscular paralysis were studied in guinea pigs. Although each component of the surface-recorded MLR was altered by barbiturate and nonbarbiturate agents, the early positive wave (wave A) was always present, and the later waves were generally identifiable at moderate levels of anesthesia. MLR threshold was not affected by anesthesia or curare. Pentobarbital, chloral hydrate, and ketamine each caused an increase in the latency of all MLR components, with increases progressively marked for later waves. Amplitude changes were more complex. Wave A increased in amplitude with anesthesia, while wave C decreased or disappeared temporarily. Wave B showed mixed amplitude changes. Changes in MLR associated with anesthesia were generally more pronounced at a stimulation rate of 10/sec as compared to 4/sec. No changes in waveform morphology or latency were seen with neuromuscular paralysis. The results provide evidence in support of separate neurogenic substrates for the different components of the guinea pig temporal lobe MLR. The presence of the MLR with moderate levels of anesthesia indicates that this animal is an appropriate model for studying the MLR in experiments requiring anesthesia and immobilization.
On the afternoon of 7 May 1915 the Cunard Liner Lusitania was torpedoed by a German U-boat whilst en route to Liverpool. Consequently in sank with the loss of 1,195 lives. A series of investigative and formal research exercises, undertaken in the light of eye-witness accounts of the events surrounding that tragedy, has given rise to a number of hypotheses concerning the loss of this vessel. In this paper all the available evidence concerning the attack, and the one or more explosions that occurred, is summarised. The conclusions regarding the torpedo effects and the most likely causes of the secondary events are reported.
UNLABELLED: The objective of the present preliminary study was to determine if a difference in the pattern of gene expression exists between tumors that were subsequently found to be sensitive to radiotherapy and tumors found to be resistant to radiotherapy. PATIENTS AND METHODS: A total of 16 patients with invasive squamous cell carcinoma of the uterine cervix were included in this study. All patients were treated with standardized radiotherapy alone. Ten of the tumors were clinically radiosensitive and six were radioresistant. Total RNA, extracted from tumor specimens obtained prior to treatment, was hybridized onto an oligonucleotide microarray with probe sets complementary to over 20,000 transcripts. The genes were first subjected to a statistical filter to identify genes with statistically significant differential expression levels between those that were radiosensitive and those that were radioresistant. A back-propagation neural network was then constructed to model the differences so that patterns could be easily identified. RESULTS: Although a number of genes were found to express differentially between radiosensitive and radioresistant tumors; the 10 most discriminating genes were used to construct the model. Using the expressions from these 10 genes, we found that neural networks constructed from random subsets of the whole data were capable of predicting radiotherapy responses in the remaining subset, which appears stable within the dataset. DISCUSSION: This study shows that such an approach has the potential to differentiate tumor radiosensitivity, although confirmation of such a pattern using other larger independent datasets is necessary before firm conclusions can be drawn.
In the present study, we report the chromosomal localization of the human 5-HT1F receptor gene (HTR1F) by the analysis of somatic cell hybrids. Based upon the HTR1F cDNA sequence, a primer set that reacted with human genomic DNA but not mouse or hamster genomic DNA was derived from the relatively nonconserved 5'-untranslated and coding region. Using monochromosomal hybrid cell lines of the NIGMS Mapping Panel 2 we localized the HTR1F to human chromosome 3. To confirm the localization on chromosome 3 and to further sublocalize the HTR1F gene, a set of human cell hybrids regionally separating chromosome 3 into 7 regions was similarly analysed. Analysis of this regional panel showed that the HTR1F gene was located proximal to the 3p14.1 breakpoint in hybrid APH14 and distal to the breakpoint in 3p13 in hybrid APH13. This localizes the HTR1F gene to human chromosome 3p13-p14.1.