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Biomedical subjects

R W Hall

Publications and source records attributed to R W Hall.

At least 19 recordsLinked to original sources
PubMed1994

Optimal location for a helicopter in a rural trauma system: prediction using discrete-event computer simulation.

A discrete-event computer simulation was developed using the C programming language to determine the optimal base location for a trauma system helicopter in Maine, a rural area with unevenly distributed population. Ambulance run reports from a one-year period provided input data on the times and places where major injuries occurred. Data from a statewide trauma registry were used to estimate the percentage of cases which would require trauma center care and the locations of functional trauma centers. Climatic data for this region were used to estimate the likelihood that a helicopter could not fly due to bad weather. The incidence of trauma events was modeled as a nonstationary Poisson process, and location of the events by an empirical distribution. For each simulated event, if the injuries were sufficiently severe, if weather permitted flying, if the occurrence were not within 20 miles of a center or outside the range of the helicopter, and if the helicopter were not already in service, then it was used for transportation. 35 simulated years were run for each of 4 proposed locations for the helicopter base. One of the geographically intermediate locations was shown to produce the most frequent utilization of the helicopter. Discrete-event simulation is a potentially useful tool in planning for emergency medical services systems. Further refinements and validation of predictions may lead to wider utilization.

Air Ambulances↗
PubMed1990

Excretion of diazepam and its metabolites in human milk during withdrawal from combination high dose diazepam and oxazepam.

The excretion of diazepam, N-desmethyldiazepam, temazepam and oxazepam in breast milk was studied during withdrawal of a 22-year-old patient from combined high dose diazepam and oxazepam therapy. Concentrations of these benzodiazepines in plasma from both the woman and her nursing infant (1 year old) were also documented. Diazepam, N-desmethyldiazepam, temazepam and oxazepam were found in the maternal plasma and milk with mean milk: plasma ratios of 0.2, 0.13, 0.14 and 0.10 respectively. It was calculated on a mg kg-1 basis that the infant received some 4.7% of the maternal dose. Diazepam could not be detected in the infant's plasma, but low levels of N-desmethyldiazepam (20 and 21 micrograms l-1), temazepam (7 micrograms l-1) and oxazepam (7.5 and 9.6 micrograms l-1) were present. The infant showed no overt physical or mental symptoms of benzodiazepine intoxication.

Adult↗
PubMed1987

Aspirin and Reye's syndrome--do parents know?

Amid growing concern over the association between aspirin and Reye's syndrome, the Aspirin Foundation has recently mounted a publicity campaign advising against the use of aspirin in children. Of 50 parents questioned at a children's ward of a district general hospital, 46 (92%) had heard of the publicity, 38 via the television. The number of parents who would give aspirin to their child had dropped significantly from 45 before the campaign to five after it (P<0.001); only one parent chose to ignore the advice. The media, particularly television, is again shown to be a potent means of publicity. Despite the very high response to the advice about aspirin none of the parents mentioned Reye's syndrome as the reason.

Aspirin↗
PubMed1984

The critical interval in dolphin echolocation: what is it?

A backward masking function relating target detection to masker delay was generated for a bottlenosed dolphin in an active echolocation target detection task. The masker was triggered by each outgoing echolocation click and could be temporally adjusted from coincidence with the target echo to delays of 700 microseconds. The animal reported target condition using a go/no-go response procedure. A modified method of constants was used to present the four masking delay intervals. Results indicated that 700- and 500-microseconds delays had little effect on target detection. However, as the delay was reduced to 100 microseconds, detection dropped to chance performance. The calculated 70% detection threshold corresponded to a delay of 265 microseconds. The results are discussed in support of the view that time separation pitch (TSP) may be an analytic mechanism used by the dolphin to discern various within-echo target attributes rather than an analytic mechanism for determining target range.

Animals↗
PubMed1983

Image processing algorithms for eye movement monitoring.

Image processing algorithms useful for the optical monitoring of eye movements have been developed and evaluated. Specifically, algorithms have been developed which track the positions of moving convex targets. Three search strategies are considered which make varying use of a priori knowledge of target position and require varying levels of random access to the image space. Results indicate that straightforward algorithms implemented with relatively slow microcomputers can yield sample rates well in excess of standard TV field rates.

Eye Movements↗
PubMed1982

Pattern processing and slow waves in visual cortex of visually deprived cats.

The slow-wave response recorded from electrodes within the visual cortex of the awake cat has been shown to reflect the pattern processing activities of the visual cortex. In a cat deprived of pattern vision by monocular lid closure, the response evoked from the non-deprived eye by patterned and diffuse stimuli show differences similar to those found in a normal cat. However, when these same stimuli are presented to the deprived eye, the differences are not present. These slow-wave data confirm previous data from single unit recordings in showing that pattern processing is altered by deprivation.

Animals↗
PubMed1981

Pattern processing and slow-wave activity in visual cortex of cat.

Animal models play a significant role in research on human disorders. In vision research, the recording of single-neuron activity from animals has been of great value to our understanding of pattern processing mechanisms. In humans, investigations of visual function have typically utilized slow-wave activity. We have studied in cats the relationship between pattern processing and the slow-wave evoked response recorded from cortical areas 17, 18, 19 and 4 in the awake cat. We have found that within a restricted latency range the response in 17, 18 and 19 reflects the processing of the patterness of a visual stimulus. A comparison of response components occurring prior to 50 msec poststimulus showed few significant differences (P less than 0.05) between peak amplitudes evoked by a diffuse and a checkerboard pattern stimulus. A much higher proportion of response components occurring after 50 msec but prior to 300 msec poststimulus were significantly different (P less than 0.05). The response recorded from area 4 (motor cortex) did not show significant differences as a function of the diffuse and patterned stimuli. Our findings show that the slow wave recorded from cat visual cortex can reflect the pattern processing mechanisms of visual cortex. Since slow waves are used in the study of visual functions in humans, the slow wave may have an important role to play in animal models of visual disorders in humans.

Animals↗
PubMed1980

Production and persistence of antibodies in chickens to sheep erythrocytes. 2. Resistance to infectious diseases.

A line of chickens selected for ability to product high antibody titers to sheep red blood cells exhibited stronger antibody to Newcastle disease, was more resistant to Mycoplasma gallisepticum, Eimeria necatrix, a splenomeglia virus, and feather mites and less resistant to Escherichia coli and Staphylococcus aureus infection than a line selected for a lack of ability to produce antibody titers. A line of chickens selected for a nonpersistance of antibody titers to sheep red blood cells was relatively more susceptible to all infectious agents tested than a line selected for a persistence of atibody titers.

Animals↗
PubMed1977

Synthesis of LH-RH by rat hypothalamic tissue in vitro. II. Effect of short-term orchiectomy and estradiol benzoate therapy.

Normal, castrate and estradiol benzoate (EB; 1 microgram/100 g b.w. x 6d, s.c.)-treated castrate male rats were utilized to study the short term effects of these treatments upon the incorporation of 3H-glycine into LH-RH in vitro. The rise in serum LH and FSH observed in the untreated castrates was prevented by EB therapy. The treatment had no significant effect upon serum LH-RH levels or the incorporation of 3H-gly into LH-RH. EB treatment markedly (p less than 0.01) increased the hypothalamic LH-RH concentration and significantly lowered the specific activity (nCi/ng) of the 3H-gly-LH-RH (p less than 0.05). These results suggest that EB acts both on the pituitary and hypothalamus to suppress gonadotropin (Gn) release, but that, at the time period studied, neither castration or EB-treatment had any apparent effect upon hypothalamic LH-RH synthesis.

Animals↗
PubMed1976

Synthesis of LH-RH by rat hypothalamic tissue in vitro: I. Use of a specific antibody to LH-RH for immunoprecipitation.

Following the procedure of Jeffcoate et al. [1974] we have successfully obtained a specific antiserum to LH-RH in rabbits, and are utilizing our antibody to study the synthesis of LH-RH by rat hypothalamic tissues in vitro. Our antibody, used at a dilution of 1:20,000, binds 37% of added 125I-labelled LH-RH, and cross-reacts minimally with thyrotropin releasing factor (TRF; 4.0%), somatotropin release inhibiting factor (SRIF; 0.035%), and melanocyte inhibiting factor (MIF; 0.009%). The antiserum recovers LH-RH added to charcoal-stripped rat serum quantitatively. Serial dilutions of rat hypothalamic extract and varying aliquots of normal rat serum are parallel to the standard curve (synthetic LH-RH: 0-100 pg/tube). Hypothalamic tissue of 4 male rats, bounded by the optic chiasm, mammillary bodies and hypothalamic fissures to a depth of 2-3 mm, was pooled, minced and incubated for 1-3 h in 2 ml of Eagle's Minimum Essential Medium in atmosphere of 95% O2/5% CO2 with 10 muCi of 3H-glycine. Reactions were stopped by the addition of 1 ml 0.1 N HC1. The tissue and medium were homogenized together and boiled for 3 min. Aliquots from the incubates were neutralized, LH-RH levels measured by radioimmunoassay (RIA), and 3H-glycine incorporation determined by immunoprecipitation, using our antibody. 3H-glycine incorporation into presumptive LH-RH increased linearly over the 3 h period. Aliquots of the 3 h incubates were chromatographed on Sephadex G-25 columns (1 x 10 cm) using 0.01 M acetic acid for elution; 1 ml fractions were collected. Synthetic LH-RH was chromatographed in a similar manner, and its elution profile determined by UV absorbance at 280 mm. Aliquots of each fraction of the eluted material from the 3 h incubates were counted in a scintillation counter to determine the elution pattern of the labelled material. Additionally, aliquots from the 1 ml fractions were neutralized and used for immunoprecipitation. Coincident peaks of 3H-label, immunoprecipitable 3H-labelled presumptive LH-RH, and synthetic LH-RH were observed. These results lend strong evidence to support our conclusion that the technique of immunoprecipitation is an efficacious approach to the study of the synthesis of LH-RH by rat hypothalamic tissue in vitro.

Animals↗
PubMed1976

Infective endocarditis following human-to-human enterococcal transmission: a complication of intravenous narcotic abuse.

Two heroin addicts, husband and wife, who shared injection paraphernalia extensively, developed enterococcal endocarditis within six weeks of one another. The etiologic organisms were of the same subspecies and had identical antibiotic susceptibilities and biochemical profiles. The clinical, epidemiologic, and bacteriologic data strongly suggest human-to-human transmission of the pathogen.

Adult↗
PubMed1975

The effect of artificial cryptorchidism on serum oestrogen and testosterone levels in the adult male rat.

Oestrone, oestradiol and testosterone levels were measured by radioimmunoassay in male rats 0.5, 1, 4, 8 and 16 days after rats were either made artifically cryptorchid or sham-operated. Oestradiol levels were not significantly different between cryptorchid and control rats 12 h or 1 day after surgery, but levels in cryptorchid animals fell to 35% of controls on day 4 (P less than 0.05), 31% on day 8, and 29% on day 16 (P less than 0.01). Conversely, oestrone and the total of the two oestrogens was higher in cryptorchid rats at one-half day (P less than 0.05), but did not differ at any other time. Testosterone levels were generally lower in cryptorchid rats than in controls. The minor contribution of oestradiol to total oestrogen levels and the lack of change of total oestrogens in cryptorchid rats led to the conclusion that oestrogens are probably not the tubular regulator of FSH in the male.

Animals↗