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Biomedical subjects

B L Smith

Publications and source records attributed to B L Smith.

At least 235 records · Page 13Linked to original sources
PubMed1984

The influence of chemical form of zinc on the effects of toxic intraruminal doses of zinc to sheep.

The EDTA, sulphate and oxide compounds of zinc were administered to sheep as a single intraruminal dose (480, 240 or 120 mg Zn per kg body weight) or as thrice-weekly doses (240 mg Zn per kg body weight per dose) for 4 weeks. In the single-dose experiment, serum zinc concentrations rose most rapidly, were highest and fell most rapidly in those animals receiving zinc EDTA. In the sheep receiving the sulphate, serum zinc concentrations were high and stayed high for 2 or 3 days. Zinc oxide caused slight, but prolonged, elevation of serum zinc. High concentrations of zinc were present in urine after administration of zinc EDTA. In the multiple-dose experiments, the sheep dosed with zinc sulphate showed progressively higher elevations of serum zinc (first dose, 5-10 micrograms Zn ml-1; day 13, 30-60 micrograms Zn ml-1) and six of the seven sheep so dosed died before the final dose. At post mortem examination, many of these had lesions of the upper gastrointestinal tract and showed evidence of haemolytic crises. Sheep dosed with zinc oxide also had progressively higher peak serum zinc concentrations. In contrast, the peak serum concentrations for the zinc EDTA-dosed sheep declined as the experiment progressed. No deaths occurred in the sheep dosed with zinc oxide or EDTA. Major pancreatic injury occurred in sheep dosed with the sulphate or oxide, but was only mild in the sheep dosed with the zinc EDTA. Diarrhoea was mild and transitory in the EDTA-dosed sheep, but more severe and persistent in those dosed with the sulphate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Initial observations concerning developmental characteristics of labio-mandibular kinematics.

Acoustic measurements have shown that children's segment durations are often longer than those of adults. It is unclear from previous research, however, why this occurs. One possibility is that children's less mature peripheral speech mechanisms limit the rate at which they can perform articulatory movements and that this results in longer acoustic segment durations. Another possible cause of children's longer segment durations is that "higher-order," organizational factors might affect their ability to plan and sequence phonetic strings. This too could limit the rate at which they produce speech gestures, thus resulting in longer segment durations. The present study attempted to clarify such issues by obtaining articulatory movement data from four children and three adults using strain gage instrumentation to monitor superior-inferior lip and jaw displacement and velocity. Results indicate that the children tended to move their articulators more slowly than the adults, despite the fact that both groups exhibited comparable articulatory displacements. Differences observed between the adults and children concerning vocal tract size and movement variability indicate that "lower-level," physical factors may be partially involved in children's slower articulatory movements. However, differences between the two groups regarding anticipation of certain articulatory sequences suggest that "higher-order," organizational effects may also be associated with children's slower movements and, therefore, their longer segment durations.

Child↗
PubMed1984

Perception of the voiced-voiceless contrast in syllable-final stops.

A computer editing technique was used to remove varying amounts of voicing from the syllable-final closure intervals of naturally produced tokens of /p epsilon b, p epsilon d, p epsilon g, pag, pig, pug/. Vowels for all six syllables were approximately the same duration, and the final release bursts were retained. Identification results showed that voiceless responses tended to occur in relatively large numbers when all of the closure voicing and, in most cases, a portion of the preceding vowel-to-consonant (VC) transition had been removed. A second experiment demonstrated that removal of final release bursts had very little effect on the identification functions. Acoustic measurements were made in an attempt to gain information about the acoustic bases of the listeners' voiced-voiceless judgments. In general, stimuli that subjects tended to identify as voiceless showed higher first-formant offset frequencies and shorter intensity decay times than stimuli that subjects tended to identify as voiced. However, for stops following /i/ and /u/ these acoustic differences were relatively small. We were unable to find a single acoustic measure, or any combination of measures, that clearly explained the listeners' voiced-voiceless decisions.

Cues↗
PubMed1984

Efficacy of diaminodiphenylsulfone and other drugs in murine Pneumocystis carinii pneumonitis.

The purpose of this study was to identify new drugs for the prevention and treatment of Pneumocystis carinii pneumonitis (PCP) induced in rats by continuous daily dosage with dexamethasone. Initially, test drugs were administered prophylactically as a screen for efficacy. Drugs were selected because of their known activity against certain protozoa and their tolerance in human usage. Doses were based on previous studies in rats or estimated from usage in humans and lower animals. Allopurinol (50 mg/kg per day), ketoconazole (25 mg/kg per day), difluoromethylornithine (2.5 g/kg per day), diloxanide (125 mg/kg per day, nifurtimox (100 mg/kg per day), suramin (20 mg/kg per day), melarsoprol (20 mg/kg per day), gentian violet (0.5 mg/kg per week, 5 and 50 mg/kg per day), primaquine (5.6 mg/kg per day) and chloroquine (37.5 mg/kg per day) were ineffective, whereas diaminodiphenylsulfone (daspone) (25 mg/kg per day) was totally effective in preventing the infection. Diaminodiphenylsulfone was then evaluated at dose levels of 5, 25, and 125 mg/kg per day and compared with trimethoprim-sulfamethoxazole (TMP-SMZ), given at 50 per 250 mg/kg per day orally. The two highest dose levels of diaminodiphenylsulfone and TMP-SMZ prevented the infection in all of the animals, and the lowest dose of diaminodiphenylsulfone prevented it in 40% of the rats. All of the untreated controls developed PCP. To determine therapeutic efficacy, animals with extensive PCP were treated for 2.5 weeks with diaminodiphenylsulfone or TMP-SMZ. Based on residual extensive pneumonitis at the completion of treatment, the pneumonitis was reduced to 50% by TMP-SMZ and to 25% by diaminodiphenylsulfone, whereas 100% of untreated controls had extensive PCP. When treatment was begun earlier in the course of the pneumonitis, diaminodiphenylsulfone was totally effective in eradicating the infection. These results suggest that diaminodiphenylsulfone is an effective drug for the treatment and prevention of murine PCP and that it is at least as effective as TMP-SMZ.

Animals↗
PubMed1984

Hypocalcaemia associated with high dose rates of zinc oxide to lactating dairy cows.

Clinical hypocalcaemia was associated with single doses of three oi more days; supply of zinc oxide to dairy cows for facial eczema control. Experimental hand dosing of a single dose of zinc oxide (40 and 120 mg Zn/kg b wt) to Jersey cows caused a significant drop in serum calcium concentration at 24 h followed by a rise to concentrations higher than controls at subsequent samplings over four days. At the highest zinc dose rate, 78% of serum calcium values were equal to or lower than the lowest control value at 24 h post dosing. Serum magnesium concentrations had a reciprocal relationship to the calcium levels at all samplings. Serum zinc concentrations were most elevated over the 48 h post dosing, returning to normal levels at the fifth day. Following the highest zinc dose milk yields were reduced by approximately 1.5 kg milk/cow/day for 48 h. Similar results were obtained when cows grazed pasture on which large amounts of zinc oxide had been sprayed.

Journal Article↗
PubMed1984

Effect of oral doses of zinc oxide on the secretion of pancreatic juice and bile in sheep.

Three sheep were given zinc oxide three times a week for six weeks at a dose rate of 240 mg zinc kg-1. The pancreatic injury resulting from the zinc oxide dosing varied from minor to severe. There was a large reduction in the rate of flow of pancreatic juice and in the concentrations of protein and amylase in the pancreatic juice from the extensively injured pancreas. Before dosing with zinc oxide, the zinc concentration in pancreatic juice was greater than in bile and increased markedly after zinc oxide dosing commenced. After prolonged dosing, zinc concentrations and output in pancreatic juice varied inversely with the degree of pancreatic injury. The bicarbonate concentration in pancreatic juice was unaffected by the zinc treatment but total output was reduced in the most severely affected sheep because flow rate decreased. In this sheep biliary bicarbonate concentration but not total bicarbonate output was increased.

Administration, Oral↗
PubMed1984

Hypertension following carotid endarterectomy: the role of cerebral renin production.

The cause of hypertension in the immediate postoperative period after carotid endarterectomy is unknown. In order to elucidate the etiology of hypertension following carotid endarterectomy, blood samples were drawn intraoperatively from internal jugular vein and external carotid artery prior to and subsequent to carotid endarterectomy in 20 patients. Renin measurement in these samples produced a ratio of internal jugular vein (cerebral) to external carotid artery (systemic). In pre-endarterectomy samples, this cerebral-to-systemic ratio was 1.0 +/- 0.17. However, in the six patients hypertensive postoperatively, this ratio was significantly (p less than 0.02) higher at 1.39 +/- 0.4 than in 14 patients not hypertensive, 0.99 +/- 0.28. Although this ratio in hypertensive patients reverted to 1.12 +/- 0.24 in the postoperative period, the present study suggests a relation between hypertension after carotid endarterectomy and renin production by the brain.

Aged↗
PubMed1983

A longitudinal study of the development of stop consonant production in normal and Down's syndrome children.

In order to compare phonological development in normal and Down's syndrome children, longitudinal observations were made of four normal children from 18 to 36 months of age and five Down's syndrome children from 3 to 6 years of age. Singleton stops and stop clusters were analyzed to determine if the Down's syndrome children evidenced phonological processes and other sound patterns similar to those of the normal children. Although quite similar patterns were observed for the two groups, the Down's syndrome children showed considerable delay in comparison to the normally developing children.

Child↗
PubMed1983

Lysis of Chinese hamster embryo fibroblast mutants by human natural cytotoxic (NK) cells.

The nontransformed, nontumorigenic CHEF/18 Chinese hamster embryo fibroblast line, as well as nontumorigenic CHEF/18 mutants that had become anchorage independent or acquired a reduced serum requirement for growth, and fully transformed, tumorigenic CHEF cell lines were analyzed for their sensitivity to killing in vitro by human natural killer (NK) cells. Nontumorigenic but transformed anchorage-independent and low-serum-requiring mutants remained insensitive to NK-mediated lysis like the parent CHEF/18 line. Only fully tumorigenic CHEF lines were found to be sensitive to NK-mediated lysis, although a few tumorigenic lines were resistant to NK lysis. These results indicate that NK sensitivity is not the result of any cellular changes associated with acquisition of an anchorage-independent or low-serum-requiring phenotype but is the result of some additional change(s) found only in fully tumorigenic CHEF cells. Our studies also show that, whatever the NK target structure is, it is evolutionarily conserved so that human NK cells are able to distinguish between Chinese hamster tumorigenic and nontumorigenic cells.

Animals↗
PubMed1983

Experimental manipulation of speaking rate for studying temporal variability in children's speech.

Children's speech timing is often more variable than adults'. In the present study, two hypotheses that have been proposed to account for this observation are considered. One claims that children do not have neuromotor control capabilities comparable to adults. The other suggests that the greater variability is a statistical consequence of children's longer segment durations. These two hypotheses were examined by having children and adults speak at both faster and slower rates than normal. Within-group comparisons across different rates and between-group comparisons for similar durational values were made from spectrographic measurements. Results indicate that both statistical and neuromotor factors seem to contribute to the greater variability commonly observed in children's speech.

Adult↗
PubMed1983

Intermittent chemoprophylaxis for Pneumocystis carinii pneumonia.

An intermittent regimen of trimethoprim-sulfamethoxazole was tested in the corticosteroid-treated rat model to learn whether or not administration for 3 consecutive days a week would provide prophylaxis equal to continuous daily doses. Although all of the untreated control animals acquired Pneumocystis carinii pneumonia, none of the animals given either continuous or intermittent trimethoprim-sulfamethoxazole became infected.

Animals↗
PubMed1983

Radiation exposure and associated risks to operating-room personnel during use of fluoroscopic guidance for selected orthopaedic surgical procedures.

Because of the increased use of fluoroscopic guidance techniques in certain orthopaedic surgical procedures, surgeons and other operating-room personnel who are involved in these procedures are voicing growing concern over possible associated radiation health hazards. Using thin-layer lithium fluoride chips for thermoluminescence dosimetry, we directly measured the radiation exposure encountered by the primary surgeon during seven operative procedures that were done utilizing fluoroscopic guidance techniques. Dosimetry studies were also carried out using a tissue-equivalent phantom model to determine the directions of maximum scatter radiation. These studies indicated that the standard protective apron that is commonly worn during the use of fluoroscopy provides adequate protection to most of the body; however, the surgeon is exposed to significant levels of scatter radiation to the head, neck, and hands, Dosimetry studies showed that positioning the fluoroscopic beam vertically to the fracture site of the supine patient, with the x-ray source posterior to the patient, provided the lowest levels of scatter radiation to the surgeon in the normal working position.

Fluoroscopy↗
PubMed1982

Genetic analysis of tumorigenesis: X. Chromosome studies of transformed mutants and tumor-derived CHEF/18 cells.

Chinese hamster embryo fibroblast cell line CHEF/18 is stably diploid, anchorage-dependent, has a high serum requirement, and a does not form tumors in nude mice. The chromosome constitutions of spontaneous and chemically induced anchorage-independent and/or low-serum CHEF/18 mutants and tumors produced in nude mice by some of these mutants are compared. We find a correlation between diploidy and nontumorigenicity among the anchorage-independent mutants but not in the low-serum mutants. One of the four spontaneous and six of the 15 chemically induced anchorage mutants have remained diploid. The remaining 12 mutants are pseudodiploid or aneuploid, and seven of them contain changes in chromosome 1, either a translocation or a deletion involving breakage at the same position (1q11-12). Each of the tumors induced by six mutants has a unique pattern of rearrangements; however five of the six have changes involving chromosome 3. This chromosome was also frequency rearranged in tumor-derived cells previously investigated.

Aneuploidy↗
PubMed1982

DNA transfer of focus- and tumor-forming ability into nontumorigenic CHEF cells.

CHEF/18 fibroblastic cells derived from a Chinese hamster embryo are diploid and nontumorigenic and require multiple steps of chemical treatment and selection to produce tumorigenic derivatives. In this report, CHEF/18 cells and a mutant capable of growing in medium with a low concentration of serum, LS1-1, were recipients in DNA transfer experiments using the calcium phosphate coprecipitation method. Focus formation with donor DNAs from tumor-derived CHEF cells and from human bladder carcinoma cell line EJ gave yields of 0.02-0.59 focus per microgram of DNA per 10(6) recipients. In one experiment in which CHEF/18 cells were transfected with EJ DNA, the presence of human DNA was detected in five of seven foci by using a cloned Alu sequence. Cells from one of these foci gave rise to tumors in nude mice, and the DNA produced secondary CHEF/18 transfectants. Because normal human cells as well as CHEF/18 cells require multiple stages to become tumorigenic, these findings suggest that EJ cells contain tumor-inducing DNA as the result of prior changes that occurred during the development of this carcinoma.

Animals↗