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Biomedical subjects

K L Smith

Publications and source records attributed to K L Smith.

At least 19 recordsLinked to original sources
PubMed1992

Determination of conditions for optimum resolution of a high angle thin window energy dispersive spectrometer.

The energy resolution of an energy dispersive spectrometer (EDS) equipped with an ultrathin window (UTW) and mounted at a high take-off angle (72 degrees) on a transmission electron microscope has been studied under a variety of operating conditions. The spectrometer resolution is close to that specified by the manufacturer, up to count rates of 400 cps. Above 400 cps the resolution deteriorates rapidly, and the MCA dead time and zero width increase. Above 10 keV, the height of the background is much greater than expected for bremsstrahlung and shows the shape which has previously been attributed to backscattered electron flux into the detector. It is postulated that the deterioration in resolution with count rate is caused by backscattered electrons reaching the detector through the UTW.

Electron Probe Microanalysis↗
PubMed1992

Lateral band translocation for swan-neck deformity.

Lateral band translocation involves transfer of the dorsally subluxed radial lateral band to the palmar aspect of the joint where it is maintained by a sling created between the flexor superficialis tendon and the palmar plate. Thirty fingers with swan-neck deformity of differing causes and a preoperative hyperextension deformity averaging 16 degrees were treated. After operation all swan-neck deformities were corrected and the average flexion contracture was 11 degrees. The range of preoperative flexion was either regained or improved. There were no recurrences and no complications. This relatively simple procedure is an effective treatment of swan-neck deformity and an attractive alternative to previously described procedures.

Female↗
PubMed1992

Displacement of an uncemented acetabular component after dislocation of a total hip prosthesis. A case report.

Review of the literature reveals few reports of complications encountered with noncemented acetabular components; most concern problems with screw or cup placement, component wear or migration, or disassembly of modular components. No reports involving the displacement of a noncemented acetabular component were found. This is a case report of a patient in whom a noncemented acetabular component was dislodged after the closed reduction of a dislocated total hip prosthesis 4.5 weeks after surgery. In light of this case, the authors believe these reductions should be performed under general anesthesia with fluoroscopic guidance. Care must be taken at surgery to ream sufficiently and obtain proper cup fit and position. Finally, the authors recommend bicortical screw fixation to provide maximum contact and rigid fixation in the early postoperative period.

Acetabulum↗
PubMed1992

Prevention of human rotavirus-induced diarrhea in gnotobiotic piglets using bovine antibody.

The efficacy of passively administered bovine antibody for preventing human rotavirus (HRV)-induced diarrhea was investigated using a gnotobiotic pig model. Cows were immunized with inactivated HRV serotypes 1 (Wa) and 2 (S2) and simian rotavirus serotype 3 (SA11), and immune colostrum and milk were collected. Antibody concentrates derived from these materials were fed to germ-free piglets that were subsequently inoculated with HRV Wa. Both viral shedding and diarrhea were effectively reduced or eliminated in a dose-dependent manner as a result of HRV immune antibody feeding. A quantitative virus-neutralizing (VN) antibody method permitted assessment of the functional antibody dose required to achieve a 50% reduction of disease (PD50). PD50 dose levels of 15.8 and 19.5 x 10(6) VN antibody units were determined for inhibition of diarrhea and viral shedding, respectively. Studies reported here provide new information on the quantitative relationship between protective antibody dose and diarrheal disease response.

Animals↗
PubMed1992

Observations on the inhibition of serum and cell surface enzymes by eicosapentaenoic acid.

The relationship between serum and tumour cell surface proteolytic enzymes and the development of muscle breakdown in cancer cachexia has been studied in a murine model of the condition (MAC16). The surface of the MAC16 tumour cells carried a proteolytic enzyme referred to as guanidinobenzoatase (GB). Serum from mice also contained an enzyme (referred to as MSE) which cleaved the trypsin inhibitor 4-methylumbelliferyl-p-guanidinobenzoate as a true substrate, but there was no relationship with weight loss or the presence or absence of tumour and the level of this serum enzyme. Polyunsaturated fatty acids (PUFAs) were shown to be inhibitors of MSE at microM concentrations and one PUFA, eicosapentaenoic acid (EPA) was found to be a non-competitive inhibitor of both MSE and GB. The effect of EPA was specific since other proteolytic enzymes, trypsin, esterase and tissue plasminogen activator were unaffected by concentrations inhibiting GB and MSE. MSE and GB are two different enzymes which possess some common properties. However, GB is likely to be significant for tumour development since MSE is also found in normal mouse serum.

Animals↗
PubMed1992

Opsonic activity of bovine serum and mammary secretion after Escherichia coli J5 vaccination.

Six pairs of cows were used to determine the effects of immunization with an Escherichia coli (O111:B4) J5 bacterin on in vitro opsonization of a smooth heterologous strain of E. coli. One cow in each pair was either immunized with the vaccine or sham-immunized at drying off, 30 d after drying off, and at calving. Opsonizing bacteria with serum collected from vaccinated cows 21 d after calving resulted in higher mean number of intracellular bacteria per phagocytosing neutrophil than opsonizing bacteria with serum collected from control cows. Phagocytic parameters using serum collected at drying off and calving did not differ between treatment groups. A trend for enhanced opsonic activity of colostrum from vaccinates was noted. Enhanced opsonization by serum from vaccinated cows coincided with higher serum IgM titer to E. coli J5 whole cell antigen compared with controls. Serum IgG titers to E. coli J5 did not differ between groups. Colostrum IgG titers to E. coli J5 were greater at calving in vaccinated than in control cows. Colostrum and milk collected 21 d after calving from vaccinated cows had higher IgM titers to E. coli J5 than did mammary secretions from control cows. Numbers of intracellular bacteria per phagocytizing neutrophil were correlated positively with IgM titers to E. coli J5 in both serum and colostrum.

Animals↗
PubMed1992

Field trial to determine efficacy of an Escherichia coli J5 mastitis vaccine.

Efficacy of an Escherichia coli (O111:B4) J5 bacterin for preventing naturally occurring IMI and clinical mastitis was tested in a 2.5-yr field trial in a 225-cow commercial herd. Cows with odd-numbered identification were vaccinated, and cows with even-numbered identification served as unvaccinated controls for each lactation during the study. Immunizations were subcutaneous on the upper part of the rib cage just posterior to the scapula at drying off, 30 d after drying off, and at calving. Percentage of quarters infected at calving with Gram-negative bacteria did not differ between treatment groups. A total of 67% of Gram-negative bacterial IMI present at calving in control cows became clinical during the first 90 d of lactation compared with 20% in vaccinated cows. Rate of Gram-negative bacterial clinical mastitis was higher in control cows than in vaccinated cows during the first 90 d of lactation. Immunization with the E. coli J5 bacterin did not reduce level of Gram-negative bacterial IMI at calving but did reduce incidence of clinical mastitis.

Animals↗
PubMed1992

Bovine neutrophil responses to parenteral vitamin E.

Twenty-eight Holsteins were tested to determine effects of dietary and parenteral vitamin E supplementation during the dry period on plasma alpha-tocopherol and in vitro neutrophil functions at calving. Cows were assigned to one of four experimental groups receiving either supplemental dietary vitamin E, injections of vitamin E, both dietary and injections of vitamin E, or neither source of supplemental vitamin E during the dry period in a 2 x 2 factorial arrangement. Cows receiving parenteral vitamin E were injected subcutaneously with 3000 IU of vitamin E (dl-alpha-tocopherol) at 10 and 5 d prior to anticipated calving. Cows not receiving parenteral vitamin E were injected with a placebo. Experimental groups receiving dietary vitamin E during the dry period were supplemented with 1040 IU/d compared with none for controls. Cows injected with vitamin E had greater plasma alpha-tocopherol concentration 5 d after the first injection, at calving, and 1 wk after calving than did cows injected with placebo. Plasma alpha-tocopherol concentrations did not differ between dietary vitamin E treatment groups from calving through 4 wk postpartum. No interaction was found between dietary and parenteral supplementation of vitamin E on plasma alpha-tocopherol concentration. Neutrophils from cows injected with vitamin E had greater intracellular kill of bacteria at calving than did neutrophils from placebo-injected cows. Neither phagocytic index nor percentage of neutrophils phagocytizing differed between vitamin E-injected and placebo-injected cows. Dietary vitamin E during the dry period had no effect on neutrophil function at calving. Intracellular kill and plasma alpha-tocopherol were correlated at calving.

Administration, Oral↗
PubMed1992

Efficacy of an Escherichia coli J5 mastitis vaccine in an experimental challenge trial.

An Escherichia coli (O111:B4) J5 bacterin was tested for efficacy in reducing IMI and severity of clinical coliform mastitis in an experimental challenge trial. Ten cows were immunized at drying off, 30 d after drying off, and at calving. Ten control cows were not immunized. Right front quarters of all cows were infused with a heterologous strain of E. coli approximately 30 d after calving. Vaccinated cows had lower bacterial counts in milk and lower rectal temperatures than unvaccinated controls following intramammary challenge. Milk production and DMI were more depressed in controls than in vaccinated cows. Milk SCC did not differ between experimental groups. Mean serum IgG titer to whole cell E. coli J5 was significantly greater in vaccinated than in unvaccinated cows at 30 d after drying off, day of challenge, and 7 d postchallenge. Milk IgG titer to E. coli J5 was higher at challenge in vaccinated than in control cows. Vaccination with the E. coli J5 bacterin did not prevent IMI but did reduce severity of clinical signs following intramammary experimental challenge with a heterologous E. coli strain.

Animals↗
PubMed1992

Susceptibility of Escherichia coli isolated from intramammary infections to phagocytosis by bovine neutrophils.

Thirteen Escherichia coli isolated from naturally occurring IMI were tested for susceptibility to phagocytosis by bovine blood neutrophils. Isolates were opsonized in pooled serum collected from nine healthy lactating cows. Bacteria isolated from IMI first diagnosed within 3 d after calving were more resistant to phagocytosis than were isolates from IMI originating during either the first half of the dry period or later during lactation. Duration of the IMI was negatively correlated with both phagocytic index and percentage of neutrophils phagocytizing within bacterial isolates from IMI originating at calving and during lactation. Phagocytosis was independent of duration of IMI within isolates from IMI originating during the first half of the dry period. Susceptibility to in vitro phagocytosis by neutrophils was not related to O antigen serotype, encapsulation, or growth in dry cow secretion.

Animals↗
PubMed1992

Effect of supplementing periparturient cows with vitamin E on distribution of alpha-tocopherol in blood.

Holstein cows were fed 0 or 1000 IU/d of supplemental vitamin E during the dry period and injected with placebo or 3000 IU of vitamin E at 10 and 5 d prior to anticipated calving. Blood was collected at various times, starting at 60 d prepartum (dry off) and concluding 30 d postpartum, and separated into plasma, red blood cells, and neutrophils. Oral supplementation increased concentrations of alpha-tocopherol in plasma and red blood cells on 10 d, but not on 5 d prepartum. Injection of vitamin E increased alpha-tocopherol in plasma, red blood cells, and neutrophils at d 5 prior to and on the day of parturition. Concentrations of alpha-tocopherol and cholesterol in plasma were correlated, and both were at their nadir at parturition. Concentrations of alpha-tocopherol in plasma and red blood cells were correlated, but the correlation increased when plasma alpha-tocopherol was expressed per unit of cholesterol. alpha-Tocopherol in plasma and neutrophils had a low correlation. Injection of alpha-tocopherol increased its concentration in plasma, red blood cells, and neutrophils during the periparturient period. Concentration of alpha-tocopherol in plasma of periparturient cows may be limited by its low lipid content, and transport mechanisms for alpha-tocopherol may differ between red blood cells and neutrophils.

Animals↗
PubMed1992

The ontogeny of hippocampal local circuits and focal epileptogenesis.

Our understanding of the pathophysiological mechanisms underlying the childhood epilepsies is rudimentary at this time. However, results of recent studies in animal models have lead to a number of important hypotheses concerning age-dependent alterations in seizure susceptibility. In area CA3 of hippocampus it appears that during a critical period when this brain area is particularly prone to electrographic seizures, an overabundance of recurrent excitatory synapses may exist. At the same time the synapses themselves appear to be functionally different than their mature counterpart. Age-dependent differences in the properties of postsynaptic NMDA receptors seem to contribute to enhanced seizure susceptibility. In recent years significant progress has been made in unravelling the fundamental processes that underlie the formation of connections between developing neurons. Over-production of early-formed axon collaterals appears to be common-place in the CNS. Moreover, the selection of appropriate patterns of connectivity appear to be dependent in large part on the patterning of neurophysiologic activity. In this regard the NMDA receptor seems to play a pivotal role in synapse consolidation. Based on these observations and the central role recurrent excitation appears to play in hippocampal seizures, it seems entirely plausible that excessive abnormal neuronal discharging that occurs during seizures early in life could result in the consolidation of abnormal numbers of recurrent excitatory synapses. This miswiring of hippocampal networks might be responsible for the marked seizure susceptibility into adulthood and might even contribute to complex partial epilepsy in individuals with a history of childhood seizures.

Adult↗
PubMed1991

Anticachectic and antitumor effect of eicosapentaenoic acid and its effect on protein turnover.

The effect of the polyunsaturated fatty acids eicosapentaenoic acid (EPA) and gamma-linolenic acid (GLA) on host body weight loss and tumor growth has been investigated in mice bearing a cachexia-inducing colon adenocarcinoma, the MAC16. EPA effectively inhibited both host weight loss and tumor growth rate in a dose-related manner with optimal effects being observed at a dose level of 1.25 to 2.5 g/kg. At these concentrations host body weight was effectively maintained, and there was a delay in the progression of growth of the tumor, such that overall survival was approximately doubled in EPA-treated animals, using the criteria dictated by the United Kingdom Coordinating Committee for the welfare of animals with neoplasms. Even when tumor growth resumed, weight loss did not occur. Animals bearing the MAC16 tumor showed a decreased protein synthesis and an increased degradation in skeletal muscle. Treatment with EPA significantly reduced protein degradation without an effect on protein synthesis. The effect of GLA on both host body weight loss and tumor growth was much less pronounced than that of EPA, with an effect only being seen at a dose of 5 g/kg, at which some toxicity was observed. In vitro studies showed that while EPA was effective in inhibiting tumor-induced lipolysis, GLA was ineffective in this respect. However, prostaglandin E1, which is formed from GLA in vivo, showed partial reversal of tumor-induced lipolysis and probably accounted for the anticachectic effect of GLA. These results suggest that EPA as the pure fatty acid should be considered for clinical investigation as both an anticachectic and antitumor agent, since prior work has shown that the other major component of fish oil docosahexaenoic acid is without pharmacological activity in this system.

Animals↗
PubMed1991

Costs associated with selected preventive practices and with episodes of clinical mastitis in nine herds with low somatic cell counts.

Nine dairy herds (mean size, 149 cows) with bulk-tank milk somatic cell counts of less than 300,000 cells/ml and greater than 80% of cows with Dairy Herd Improvement Association linear somatic cell counts less than or equal to 4 were selected for study. Each herd was monitored for 12 consecutive months. Duplicate quarter-milk specimens were collected from each cow for bacteriologic culturing at beginning of lactation, cessation of lactation, and at the time of each clinical episode of mastitis. Streptococcus agalactiae was never isolated and Staphylococcus aureus was isolated from less than 1% of all quarters. There were 554 episodes of clinical mastitis. During the year of study, the incidence rate of clinical mastitis varied from 15.6 to 63.7% of cows among the 9 herds. Mean costs per cow per year in herd for mastitis prevention were: $10 for paper towels, $3 for nonlactating cow treatment, and $10 for teat disinfectants. Mean cost associated with clinical mastitis was $107/episode. Approximately 84% ($90) of the costs attributed to a clinical episode were associated with decreased milk production and nonsalable milk. Costs of medication and professional veterinary fees per clinical episode varied significantly among the 9 herds. Three of the herds did not have a veterinarian treat a clinical episode of mastitis during the year of study even though 2 of these herds had the first and third highest incidence rates of clinical mastitis. When calculated on a per cow in herd basis, mean costs of $40/cow/year were attributed to clinical mastitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Calcium modulation of the N-methyl-D-aspartate (NMDA) response and electrographic seizures in immature hippocampus.

Recordings from the CA3 region of hippocampal slices indicate a developmental change in the divalent cation sensitivity of the response elicited by N-methyl-D-aspartate (NMDA) application. In parallel experiments a developmental difference is demonstrated in the capacity of extracellular calcium to modulate electrographic seizure generation. Calcium modulation of the NMDA-elicited response may contribute to the pronounced capacity of immature hippocampus to generate electrographic seizures. Under these conditions activity dependent changes in extracellular calcium could have a greater influence on ion flow produced by activation of the NMDA receptor. The possibility that changes in the receptor isoform may occur during development would have widespread implications for normal cognitive functions and dysfunctions during brain maturation.

Age Factors↗
PubMed1991

Confocal microscopy and three-dimensional reconstruction of electrophysiologically identified neurons in thick brain slices.

Three-dimensional morphology and electrophysiology were correlated from individual neurons in a thick brain slice preparation. The hippocampal formation from immature and adult rats was cut transverse to the longitudinal axis into 500 microns-thick slices which were maintained under physiologic conditions. Individual neurons were impaled and physiologically characterized using microelectrodes. Recordings were made from the soma and in some cases from a dendrite. The impaled neurons were filled through the microelectrode with the fluorescent dye lucifer yellow and imaged by confocal scanning laser microscopy using an analog preprocessor. As many as 180 optical sections were recorded as a function of depth through the slices. Images are presented as a series of optical sections, stereo pairs, or three-dimensional reconstructions. Both stereo contouring and volume rendering methods were employed, and the reconstructions were viewed from any arbitrary perspective. Dendritic and axonal fields were separated from each other and displayed separately or as different pseudocolors. The three-dimensional reconstructions provided perspectives that were difficult or impossible to appreciate by viewing the optical sections or conventionally formed stereo pairs.

Animals↗