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Biomedical subjects

K L Smith

Publications and source records attributed to K L Smith.

At least 181 records · Page 10Linked to original sources
PubMed1991

Comparison of probiotic and antibiotic intramammary therapy of cattle with elevated somatic cell counts.

The effects of treating subclinical mastitis with intramammary infusions of either a Lactobacillus or an antibiotic preparation on intramammary infection cure rate and on milk SCC were compared. Cows with two consecutive monthly DHIA composite SCC greater than 300,000 cells/ml (5.4771 log10/ml) were defined as high SCC cows. Twenty-six subclinical cows were randomly assigned to one of two treatments. Quarter foremilk samples were obtained from all quarters at d 0, 7, and 14 following infusion to determine the microbiological status and SCC. Composite milk SCC were determined monthly by DHIA and at d 0, 7, and 14 of the study. Coagulase-negative staphylococci were the predominantly isolated pathogens. Treatment of cows with Lactobacillus cured 21.7% of infected quarters, whereas 73.7% of infections treated with antibiotic were eliminated. Treatment of quarters with antibiotic did not reduce quarter SCC unless infected quarters were cured. Intramammary infusion of quarters with Lactobacillus increased quarter SCC, mainly because of an increase in SCC of initially uninfected, low SCC quarters. Monthly composite SCC were similar between treatments. The results indicate that administering Lactobacillus or antibiotic treatment to all quarters based on elevated composite SCC should not be adopted. Lactobacillus treatment increased SCC with no effect on infection rate.

Animals↗
PubMed1991

Gram-negative bacterial infections of the mammary gland in cows.

Naturally acquired gram-negative bacterial intramammary infections (n = 160) were studied in 99 cows over a 2-year period. Escherichia coli, Klebsiella spp, Serratia spp, Enterobacter spp, and unidentified gram-negative bacteria were isolated from 28.8, 39.4, 9.4, 5.0, and 11.2%, respectively, of infected mammary glands. A majority (61%) of intramammary infections were first detected during the nonlactating period. Gram-negative bacteria isolated during the first half of the nonlactating period were predominantly Klebsiella spp, Serratia spp, and Enterobacter spp. Onset of E coli intramammary infections was more prevalent during the second half of the nonlactating period and during the first 7 days of lactation. The majority (59%) of infections were less than 28 days in duration, but Klebsiella spp and Serratia spp infections were of significantly (P less than 0.05) greater duration than infections with E coli. The greatest percentage (47%) of gram-negative bacterial intramammary infections were first detected during the summer.

Animals↗
PubMed1990

Long-term experience with a totally implanted catheter system in cancer patients.

Long-term experience with totally implanted catheter systems (TICS) is limited. We retrospectively evaluated the performance and long-term complications of TICS for intravenous infusion in cancer patients; 134 systems were implanted in 128 patients. The median duration of implantation was 144 weeks with 49 systems implanted for more than one year. Complications related to surgical factors included malposition of reservoir (2%), skin perforation or wound dehiscence (1.5%) and pneumothorax (less than 1%). Complications not related to surgical factors included: drug extravasation (1.5%), mechanical malfunction (1.5%), vein thrombosis (less than 1%), clotting of the reservoir or catheter (2%), skin infection (1.5%), and sepsis (less than 1%). The total complication rate was 13%. Most complications resolved spontaneously or with medical treatment and only 6 patients (4.6%) required re-implantation of a second system. We conclude that with long-term usage of TICS, the complication rate remains low, making it a safe and viable alternative for patients requiring long-term intravenous therapy.

Adult↗
PubMed1990

Neural networks and synaptic transmission in immature hippocampus.

The results reviewed in this chapter indicate that local circuit synaptic interactions are surprisingly well-developed in the rat hippocampal CA3 subfield during the second postnatal week. Intracellular recordings reveal large spontaneous epsps and ipsps. Synchronized bursts of synaptic potentials are observed in most paired intracellular recordings. Antidromic and orthodromic electrical stimulation evokes synaptic responses that are reminiscent of recordings from mature hippocampus. However, following brief trains of electrical stimuli and during bath application of a GABAA receptor antagonist, large prolonged depolarizations are recorded. These are suppressed by excitatory amino acid antagonists. In comparison, slices from mature rats do not produce these events under the same conditions. Thus, a hypothesis has been presented that the degree of recurrent synaptic interaction between pyramidal cells may be enhanced during this critical period in hippocampal development. An analysis of recurrent epsps using dual intracellular recordings is consistent with this contention. The degree of excitatory synaptic interaction between CA3 neurons appears to be at least equal to and likely in excess of that reported in mature hippocampus. One possible explanation for this is that the number of recurrent excitatory synapses may increase transiently during hippocampal development, only later to regress to numbers found in the adult. Recent studies of others suggest that activation of NMDA receptors may play a key role in the maintenance of synapses during development (Cline et al., 1987; Kleinschmidt et al., 1987). In this regard it is interesting that the characteristic of the NMDA receptor-ion channel complex on immature and mature rat CA3 hippocampal pyramidal cells appear to be quite different. These differences may play a role in synapse formation and maintenance. The role of NMDA receptors in LTP and learning (for review see Cotman et al., 1989; Lynch, 1986) are widely discussed. In other circles recurrent excitatory neuronal networks are thought to be substrates for memory (Lynch, 1986; Haberly and Bower, 1989). Both NMDA receptors and recurrent excitation are well represented in the CA3 subfield of immature hippocampus. One challenging area for future study will be the clarification of the interrelations between synaptogenesis and synaptic plasticity within neural networks of the developing hippocampus.

Animals↗
PubMed1990

Effects of word-onset cuing on picture naming in aphasia: a reconsideration.

When an aphasic is unable to name an object, giving the patient the opening sounds of the target name will often trigger the correct response. Eighteen aphasic subjects were tested using a gating paradigm to compare word onset durations necessary to elicit correct names after an initial naming failure with those necessary for recognizing the same words when spoken in isolation with no picture present. Prerecognition errors were also examined. Results suggested that the facilitation of naming found when examiners supply word-onset sound cues may be due in part to a two-stage process consisting of stem-completion followed by matching the picture with the potential name as generated.

Aged↗
PubMed1990

Confocal scanning laser microscope images of hippocampal neurons intracellularly labeled with biocytin.

We have assessed the properties and usefulness of confocal scanning laser microscopy in the reflection mode for the study of neuronal morphology. In this mode, the confocal microscope detects the light reflected off the specimen as opposed to the light emitted by a fluorescent label. Neurons in slices of rat hippocampus were filled with biocytin and reacted sequentially with avidin-horseradish peroxidase and nickel-intensified diaminobenzidine (DAB/Ni). In all parts of the neuron the DAB/Ni reaction product produced a strong reflection signal in the confocal microscope. The stereo images revealed aspects of three-dimensional hippocampal cell morphology such as the conical shape of the dendritic fields and a characteristic branching pattern of the axon. Labelling neurons intracellularly is an established technique for identifying physiologically-characterized neurons. Recently, confocal microscopy has become a powerful method for examining the three-dimensional morphology of biological specimens. The resulting images in this paper show that reflection-mode confocal microscopy provides an excellent representation of the filled neurons in three dimensions and presents an opportunity for correlative electrophysiological and morphological studies and extension to the electron-microscopic level.

3,3'-Diaminobenzidine↗
PubMed1990

Parameters affecting imaging of the horseradish-peroxidase-diaminobenzidine reaction product in the confocal scanning laser microscope.

Neurons intracellularly filled with biocytin and labelled with nickel-intensified diaminobenzidine (DAB/Ni) can be imaged on the confocal scanning laser microscope in order to obtain three-dimensional and optical section images of neurons. Intensification of the DAB reaction product with nickel was found to be crucial for obtaining a workable signal level. On the other hand, the high absorption of light by the reaction product severely attenuated the detection of structures lying directly underneath, and the intensity of the unattenuated laser used for imaging faded or damaged DAB/Ni reaction product. We have determined that reduction of the laser intensity combined with the use of proper objective lenses and non-laser-based imaging for preliminary adjustments of the specimen all work to reduce or eliminate damage, and also improve the image. These items must be kept in mind when imaging and analysing DAB-labelled structures in the laser-based confocal microscope.

3,3'-Diaminobenzidine↗
PubMed1990

The remediation of conduction aphasia via sentence repetition: a case study.

Repetition is viewed typically as a primary deficit in conduction aphasia. Consequently, repetition is considered to be a target of treatment, as opposed to an approach to treatment for this syndrome. However, our experience with a conduction aphasic who had greater speech fluency in repetition than in conversation encouraged us to develop a treatment programme based on sentence repetition. The treatment programme has three components: (1) a pre-/post-test of sentence repetition; (2) the treatment component, in which a new set of sentences is introduced each week in outpatient therapy for daily repetition; (3) analysis of verbal picture description prior to and following treatment as an independent language measure. The patient CM participated in 2 months of sentence repetition treatment, after which he displayed improvement in both sentence repetition and picture description. The reasons for such improvement and the general utility of the treatment programme are discussed.

Aged↗
PubMed1990

Growth of gram-negative bacteria in dry cow secretion.

Gram-negative bacteria (n = 192) isolated from infected bovine mammary glands were tested for growth in a pooled source of dry cow secretion. Growth of Klebsiella pneumoniae in dry cow secretion was greater than growth of Escherichia coli and Klebsiella oxytoca. Escherichia coli originating during the early dry period exhibited greater growth in dry cow secretion than those originating around calving or during lactation. Klebsiella pneumoniae growth did not differ with time of origin of intramammary infection. Escherichia coli, K. oxytoca, and K. pneumoniae growth in a synthetic medium was reduced by apolactoferrin plus Ig. Growth reduction was greatest for E. coli. Citrate reversed growth inhibition. The inhibitory properties of dry cow secretion for E. coli may contribute to the low number of naturally occurring intramammary infections originating during the early part of the dry period. Inhibitory properties of dry cow secretion are partially explained by lactoferrin acting in conjunction with antibody to prevent iron acquisition by many gram-negative bacteria.

Animals↗
PubMed1990

Relationships among selenium, vitamin E, and mammary gland health in commercial dairy herds.

Nine well-managed dairy herds were monitored for 1 yr to determine if bulk tank SCC and rate of clinical mastitis were associated with dietary and plasma Se and vitamin E status. Intakes of Se and vitamin E were 1 to 16 mg/d and 100 to 900 mg/d, respectively. Plasma Se concentrations were correlated positively with intakes of Se below 5 mg/d but were independent of Se intakes above 5 mg/d. Feeding vitamin E increased plasma concentrations of tocopherol, but the influence of dietary vitamin E on plasma concentrations was four times greater for dry cows than for lactating cows probably due to secretion of tocopherol into colostrum and milk. Bulk tank SCC averaged 5.4 log10/ml and decreased significantly as Se concentration in plasma increased. Plasma glutathione peroxidase was correlated positively to Se intake but negatively to SCC. Rate of clinical mastitis was negatively related to plasma Se concentration and concentration of vitamin E in the diet. An apparent interaction between dietary Se and vitamin E was evident since herds fed high amounts of Se tended to have high rates of clinical mastitis, but not if high amounts of vitamin E were fed. These data confirm earlier findings that Se and vitamin E status of dairy cows are related to mammary gland health.

Animal Nutritional Physiological Phenomena↗
PubMed1990

Intramammary challenge of the bovine mammary gland with coliform bacteria during early involution.

Isolates of Escherichia coli (n = 12), Klebsiella pneumoniae (n = 20), and Klebsiella oxytoca (n = 10) were used to challenge involuting mammary glands at 7 d of the dry period. Bacteria were selected for challenge on the basis of their ability to grow in a pooled source of dry cow secretion obtained at 21 d of involution. Challenge bacteria were classified as highly adapted (in vitro growth greater than 7 cfu log10/ml) or poorly adapted (growth less than 2 cfu log10/ml) for growth in dry cow secretion. Intramammary infusion of Escherichia coli, K. pneumoniae, and K. oxytoca resulted in 0, 40, and 30%, respectively, of quarters infected. Isolates highly adapted for growth in dry cow secretion caused 75% of K. pneumoniae and 67% of K. oxytoca experimental intramammary infections. Results indicated that the ability to overcome inhibitory properties of dry cow secretion was related to the establishment of K. pneumoniae and K. oxytoca intramammary infections in the dry gland. There was no evidence that growth of E. coli in dry cow secretion related to pathogenicity in the dry gland. Experimental challenge using multiple isolates did confirm the resistance of the involuting mammary gland to E. coli infection.

Animals↗
PubMed1990

Bacterial counts associated with recycled newspaper bedding.

Bacterial counts associated with recycled newspaper, wood shavings, and pelleted corn cobs used as bedding for lactating dairy cows were compared. Chopped newspaper and pelleted corn cobs had similar gram-negative bacterial, coliform, and streptococcal bedding counts. Staphylococcal counts in pelleted corn cobs were greater than in chopped newspaper. Conversely, gram-negative bacterial, coliform, and staphylococcal counts in chopped newspaper were greater than in wood shavings. Coliform and streptococcal counts did not differ between chopped newspaper and wood shavings bedding materials. Teat swab counts from cows bedded on pelleted corn cobs were greater than those from cows bedded on chopped newspaper for gram-negative bacterial, coliform, Klebsiella species, and staphylococci. Streptococcal teat swab counts did not differ between cows bedded on chopped newspaper and pelleted corn cobs. Cows bedded on chopped newspaper and wood shavings had similar gram-negative bacterial, coliform, and Klebsiella species teat swab counts. Streptococcal and staphylococcal teat swab counts were greater from cows bedded on chopped newspaper than those from cows bedded on wood shavings. Teat swab and bedding counts were correlated. In general, bacterial counts in bedding suggest no advantage in using chopped newspaper over pelleted corn cobs or wood shavings in reducing exposure of teats to environmental mastitis pathogens.

Animals↗
PubMed1990

Relationships among vitamin E, selenium, and bovine blood neutrophils.

Effects of vitamin E and selenium supplementation on in vitro phagocytosis and intracellular kill of bacteria by bovine neutrophils were investigated. Diets were not supplemented with vitamin E and selenium during the dry period and first 21 d of lactation. Cows were then assigned to one of four treatment diets for 30 d. Treatment diets were either unsupplemented or supplemented with vitamin E, selenium, or both vitamin E and selenium, in a 2 x 2 factorial arrangement. Peripheral blood neutrophils were isolated from each cow on lactation d 51. Vitamin E supplementation of diets increased intracellular kill of Staphylococcus aureus and Escherichia coli by neutrophils. Intracellular kill of S. aureus was greater in neutrophils isolated from selenium supplemented cows than in neutrophils from cows without supplemental selenium. Intracellular kill of E. coli did not differ between neutrophils from selenium supplemented and selenium unsupplemented cows. Ability of neutrophils to phagocytize either S. aureus or E. coli was independent of vitamin E and selenium.

Animals↗
PubMed1990

Hemagglutination and hemolysis by Escherichia coli isolated from bovine intramammary infections.

Seventy-six Escherichia coli isolated from bovine intramammary infections were tested for hemagglutination and hemolysis of erythrocytes. Fifty-seven percent of isolates were hemagglutination-positive for bovine erythrocytes compared with 46% that agglutinated guinea pig erythrocytes. Twenty-eight percent of isolates were hemagglutination-positive for erythrocytes from both species. Only 14.5 and 2.6% of isolates were mannose-resistant, hemagglutination-positive for bovine and guinea pig erythrocytes, respectively. Neither duration nor severity of infection from which isolates were obtained differed between isolates that were hemagglutination-positive and hemagglutination-negative. Percentage distribution of hemagglutination-positive isolates did not differ among isolates from infections that originated at calving, during lactation, or the first half of the dry period. Hemagglutination reactions were also not related to in vitro growth in cell-free dry cow secretion. Percent of isolates that caused hemolysis of washed bovine erythrocytes was 2.6% compared to 3.9% for sheep erythrocytes. Hemolysis was not related to hemagglutination. Hemagglutination and hemolysis of erythrocytes did not appear to be virulence factors for E. coli isolated from bovine intramammary infections.

Animals↗
PubMed1990

Effect of duration of supplementation of selenium and vitamin E on periparturient dairy cows.

Cows were fed diets either supplemented with .2 ppm Se and 70 IU vitamin E/kg diet DM (21 cows) or unsupplemented (40 cows) during the dry period (approximately 60 d). From parturition to 21 d of lactation, cows were fed diets that were either supplemented with .3 ppm Se and 40 IU/kg vitamin E or unsupplemented. At d 21 following parturition, 18 cows fed the unsupplemented diet were switched to diets containing 0 or .3 ppm supplemental Se and 0 or 40 IU/kg supplemental vitamin E arranged factorially. These diets were fed for the next 32 d. The remaining cows continued their respective diets for 32 d. Plasma Se concentrations averaged .1 microgram/ml for supplemented cows but were .05 micrograms/ml for unsupplemented cows. Plasma Se concentration from cows fed supplemental Se from 21 to 53 d postpartum increased rapidly and were not different from long-term supplemented cows. Whole blood glutathione peroxidase activity was lower in unsupplemented than in supplemented cows. Short-term Se supplementation increased glutathione peroxidase activity above that for unsupplemented animals, but activity was still less than that in long-term supplemented animals. Plasma alpha-tocopherol concentrations at parturition and d 21 postpartum were lower in unsupplemented than in supplemented animals. On d 53 postpartum, no differences in plasma alpha-tocopherol concentrations were found between long-term supplemented and unsupplemented cows. Supplementing vitamin E during the dry period increased alpha-tocopherol content of colostrum.

Animals↗
PubMed1989

A slow NMDA-mediated synaptic potential underlies seizures originating from midbrain.

After bath-perfusion with gamma-aminobutyric acid antagonists, slices of the rat's inferior colliculus were studied electrophysiologically. Synchronized epileptiform events were found to occur. The most prominent intracellular event was a sustained 30 mV depolarization which was pharmacologically and electrophysiologically characterized as an N-methyl-D-aspartate-mediated event. We propose that elicitation of this slow synaptic potential is the a priori basis of seizures arising in this midbrain nucleus.

2-Amino-5-phosphonovalerate↗