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Biomedical subjects

K L Smith

Publications and source records attributed to K L Smith.

At least 199 records · Page 11Linked to original sources
PubMed1989

Bacterial counts in bedding materials used on nine commercial dairies.

Bacterial counts were monitored for 1 yr in bedding materials used on nine commercial dairies. Organic materials used to bed lactating cows had significantly higher moisture content and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts than did inorganic materials. Klebsiella species counts were higher in sawdust than in chopped straw. Streptococcal counts were higher in chopped straw than sawdust. Bacterial counts did not differ between sand and crushed limestone. Gram-negative bacterial and coliform counts were higher during summer and fall than in winter and spring months. Streptococcal counts did not differ among seasons of the year. Linear relationships were significant between total rates of clinical mastitis during lactation and both gram-negative bacterial and Klebsiella species counts in lactating cow bedding. These data indicate that bacterial populations differed between both types of bedding and among seasons of the year. Rates of clinical mastitis were related to bacterial counts in bedding.

Animals↗
PubMed1989

Prolonged in vitro exposure of Staphylococcus aureus to germicidal teat dips.

Eight strains of Staphylococcus aureus were tested to determine if prolonged exposure to commercial teat dips could enhance bacterial tolerance to teat dips in vitro. All strains of S. aureus were serially plated 15 times on chemically defined agar medium containing sublethal concentrations of linear dodecyl benzene sulfonic acid, chlorhexidine, sodium hypochlorite, and iodophor teat dips. Growth responses of S. aureus to chlorhexidine, sodium hypochlorite, and iodophor were not affected by prolonged exposure to these teat dips. Isolates subcultured on agar containing .1% linear dodecyl benzene sulfonic acid teat dip subsequently had a greater mean growth response to .1% solution of the germicide than did controls subcultured on basal medium. Hemolytic patterns, tube coagulase, clumping factor, and protein A reactions of S. aureus were not altered by exposure to any of the teat dips tested. In general, prolonged exposure to commercial teat dips did not alter germicidal susceptibility of S. aureus.

Animals↗
PubMed1989

Field survey of clinical mastitis in low somatic cell count herds.

Nine commercial dairy herds, each with low herd milk somatic cell counts, were monitored for 1 yr to determine prevalence of intramammary infections and rates of clinical mastitis. Staphylococcus species was the bacterial group most frequently isolated from quarters at calving and at drying off. Environmental streptococci and coliform intramammary infections totaled less than 6% of quarters at both calving and at drying off. Staphylococcus aureus were isolated from less than 1% of quarters and Streptococcus agalactiae from 0% of quarters at both calving and drying off. A total of 646 clinical cases of mastitis were diagnosed in 548 quarters of 406 cows. Mean rate of clinical mastitis among herds was .457 clinical cases/305 cow-days. Rates of clinical mastitis ranged among herds from .273 to .748 clinical cases/305 cow-days. Coliforms and bacteriologically negative and environmental streptococci accounted for 82.3% of clinical cases. Rates of clinical mastitis and severity of clinical signs differed among herds, seasons of the year, parity groups, and stages of lactation. Rates of clinical mastitis were highest during summer, in first lactation cows, and during the first 7 d of lactation.

Animals↗
PubMed1989

Serum susceptibility of coliforms isolated from bovine intramammary infections.

A total of 35 coliforms isolated from bovine intramammary infections were tested for serum susceptibility. Growth responses of Klebsiella pneumoniae isolated from intramammary infections originating during the dry period were inhibited more than were growth responses of Klebsiella pneumoniae isolated from infections originating during lactation. Escherichia coli growth responses did not differ between isolates originating from dry period and lactational intramammary infections. Mean growth responses to serum did not differ between Klebsiella pneumoniae and Escherichia coli. Bactericidal properties of serum were due to complement activity. The classical pathway of complement appeared to be the principal source of bactericidal activity of serum toward Klebsiella pneumoniae. Alternative and classical pathways of complement were both important for bactericidal effects of serum on Escherichia coli. Iron saturation of serum did not affect growth responses of either Klebsiella pneumoniae or Escherichia coli. These data illustrate that coliforms isolated from intramammary infection originating during the dry period were not more resistant to the bactericidal activity of bovine serum than were coliforms isolated from intramammary infection occurring during lactation.

Animals↗
PubMed1989

Dialysate dumping: a novel cause of inadequate dialysis in continuous ambulatory peritoneal dialysis (CAPD) patients.

Inadequate control of serum chemistries and extracellular fluid volume may result in patients being changed from continuous ambulatory peritoneal dialysis (CAPD) to another form of dialysis. We report 2 patients in whom apparent inadequacy of CAPD resulted from dialysate dumping. The first patient could not control her fluid intake and required frequent hypertonic exchanges. She felt too full with these exchanges and drained a substantial portion of each exchange 30 to 60 min after infusion. Patient 2 had similar complaints but simply drained a large portion of each fresh bag directly into the drain bag at the start of the flush-before-fill step. Both patients had improved results from CAPD once they stopped their dialysate dumping. Partial wasting of each exchange because of abdominal discomfort should be added to the causes of inadequate dialysis in CAPD.

Adult↗
PubMed1989

Effects of oral base therapy on serum ionized calcium, phosphorus and parathyroid hormone in chronic hemodialysis patients.

The purpose of this study was to evaluate the effects of oral base therapy on selected chemical parameters in chronic hemodialysis patients. Oral base supplements were administered to 20 acidotic chronic hemodialysis patients for one month. Serum bicarbonate levels rose from 18.6 +/- 2.9 to 22.5 +/- 4.0 mEq/L (p less than 0.0005) and pH rose from 7.35 +/- 0.03 to 7.39 +/- 0.04 (p less than 0.0005). Serum ionized calcium levels fell from 5.03 +/- 0.37 to 4.83 +/- 0.34 mg/dL (1.25 +/- 0.09 to 1.21 +/- 0.08 mmol/L) (p less than 0.01), while intact parathyroid hormone (PTH) levels rose from 547 +/- 697 to 619 +/- 776 pg/mL (p less than 0.05). Base therapy did not result in significant changes in serum levels of total calcium, phosphorus, alkaline phosphatase, urea nitrogen, creatinine, total protein, albumin or potassium. If empiric therapy with exogenous base is given to dialysis patients, ionized calcium levels should be closely monitored since changes in calcium supplement or vitamin D therapy may be required to maintain ionized calcium and parathyroid hormone values at the pre-treatment levels.

Acidosis↗
PubMed1989

Atrial natriuretic peptide (ANP) is removed by peritoneal dialysis in humans.

Atrial natriuretic peptide (ANP) is a hormone liberated from the heart during atrial stretch (volume overload). In order to determine if ANP levels are altered in patients on continuous ambulatory peritoneal dialysis (CAPD) or affected by the dialysis procedure itself, we measured plasma ANP in patients before and after peritoneal infusion of two liters of 1.5% Dianeal dialysate and in dialysate subsequently drained from these patients. Plasma ANP is elevated in CAPD patients, but is not affected by infusion of dialysate. ANP is cleared from plasma by peritoneal dialysis.

Adult↗
PubMed1989

Inhibition of erythropoiesis by a soluble factor in murine malaria.

To study the cellular mechanisms involved in the ineffective erythropoiesis associated with malaria, an in vitro proliferative assay was used to measure the response to erythropoietin (Epo) of erythroid progenitor cells from malaria-infected mice. In this assay, spleen (SP) cells from phenylhydrazine (PHZ)-treated mice (PHZ-SP), enriched for erythroid progenitor cells, respond to Epo in a dose-dependent manner. Despite a similar degree of anemia, SP and bone marrow (BM) cells from Plasmodium berghei- or P. vinckei-infected mice did not show a significant response to Epo in this assay. When SP or BM cells from malaria-infected mice were added to cultures of SP or BM cells from PHZ-treated mice the response to Epo of these cells was significantly inhibited. Removal of parasitized red blood cells (pRBC) from SP cells of P. berghei-infected mice had no effect on the ability of the cells to inhibit the response to Epo. Adherent SP cells and SP cells positive for the Mac-1 antigen, from malaria-infected mice, were shown to be enriched for cells that could inhibit the response to Epo. Cell-free conditioned media (CM) prepared from SP cells of P. berghei- or P. vinckei-infected mice or from normal SP cells incubated with pRBC were also able to inhibit the response to Epo of SP cells from PHZ-treated mice. These investigations have shown that during the course of malaria infection, cells appear in the SP and BM capable of inhibiting, via soluble mediators, the response to Epo of erythroid progenitor cells. The cells responsible are probably macrophages. The nature of the factor(s) and its mechanism of action are not known. Through the ability to inhibit erythropoiesis, soluble factors may, in part, mediate the anemia associated with malaria.

Animals↗
PubMed1988

Immunomodulation of in vitro antigen presentation by cations.

The ability of various cations to alter an antigen-specific (ovalbumin) T cell activation system in vitro has been assessed. This in vitro system includes analysis of antigen capture, processing, and presentation by antigen presenting cells (APC) (splenocytes, B cells or macrophages) in a major histocompatibility complex (MHC) restricted fashion and the evaluation of the activation of a T-cell hybridoma, DO-11.10, which is specific for "processed" ovalbumin in association with I-Ad. Activation is determined by production of IL2 which is quantitated in a bioassay with HT-2 cells. Numerous metals (10 and 100 microM) were screened in the coculture assay (APC and DO-11.10 plus ovalbumin). Metals with inhibitory effects were Cd greater than Cu greater than Pb greater than Zn. Co and Cr had no modulatory effect and Ni had an enhancing effect (increased IL2 production). The effects of the modulatory metals were further assessed for influences on the individual cellular components of this system. Cd was toxic to all cell types whereas Cu was toxic only to irradiated splenocytes and Do-11.10. Pb was the only metal which was not toxic to any cell type but still inhibited antigen presentation. To prevent influences of metals on DO-11.10 or carryover into the bioassay, APC were preincubated with metals and then assessed for presentation capability. After preincubation, only Cd, Pb, and Cu were inhibitory. The inhibition by Cd was due to toxicity. Cu inhibited only irradiated splenocyte presentation and this effect was due to toxicity. Pb inhibition was due to a mechanism other than toxicity and its biochemical influences on APC are discussed.

Animals↗
PubMed1988

Growth responses of environmental mastitis pathogens to long-chain fatty acids.

Streptococcus uberis, Streptococcus faecalis, Escherichia coli, and Klebsiella pneumoniae were tested for susceptibility to long-chain fatty acids predominant in teat canal keratin. Antibacterial activity of free fatty acids on each bacterial species was measured after 12 h in synthetic media. Growth responses of all three strains of Streptococcus uberis were completely inhibited by C18:3 and those of two of three strains by C18:2 at 1 micrograms/ml. None of the fatty acids tested were bactericidal to Streptococcus faecalis. Saturated fatty acids C14 and C16 were more bacteriostatic to Streptococcus faecalis than were polyene fatty acids. Growth responses of coliform species were not affected by long-chain fatty acids. In general, environmental mastitis pathogens were resistant to fatty acids predominant in teat canal keratin.

Animals↗
PubMed1988

Rate of environmental mastitis in quarters infected with Corynebacterium bovis and Staphylococcus species.

Rates of environmental streptococcal and coliform intramammary infections were compared among quarters uninfected and infected with either Corynebacterium bovis or Staphylococcus species. Rate of environmental streptococcal intramammary infections was 3.9 times greater in C. bovis-infected quarters than in uninfected quarters. Rate of environmental streptococcal infections was 2.6 times greater in quarters infected with Staphylococcus species than in uninfected quarters. Rate of coliform intramammary infections did not differ among quarters with differing bacteriological infection statuses. Quarters infected with either C. bovis or Staphylococcus species had higher milk SCC than did uninfected quarters. Intramammary infection with either Corynebacterium bovis or Staphylococcus species did not protect quarters against coliform infection. Rate of environmental streptococcal infections was enhanced in quarters infected with either C. bovis or Staphylococcus species.

Animals↗
PubMed1988

Sensitivity and specificity of latex agglutination tests used to identify Streptococcus agalactiae and Staphylococcus aureus isolated from bulk tank milk.

Comparisons were made among rapid latex agglutination tests and conventional biochemical tests used to identify Streptococcus agalactiae and Staphylococcus aureus. Ninety-eight streptococci and 149 staphylococci isolated from bulk tank milk were tested. Sensitivity and specificity for the latex agglutination test used for identification of Str agalactiae were 97.6 and 98.2%, respectively. Sensitivity and specificity for the latex agglutination test used for identification of S aureus were 90.2 and 67.5%, respectively. Of 25 staphylococci considered false-positive by the latex agglutination test, 14 (56%) were considered tube coagulase-positive. Fifteen staphylococci considered false-positive by latex agglutination test had biotypes representative of S hyicus of S xylosus.

Animals↗
PubMed1987

Carbamazepine suppresses synchronized afterdischarging in disinhibited immature rat hippocampus in vitro.

Bath application of therapeutic concentrations of the anticonvulsant carbamazepine suppressed penicillin-induced synchronized afterdischarging in immature rat CA3 hippocampal pyramidal cells. Afterdischarging was completely abolished in all preparations at a concentration of 30 microM (IC50 = 8.5 +/- 1.4 microM; mean +/- S.E.M.). The duration of the preceding epileptiform burst was not altered at this concentration and was diminished by only 24.4 +/- 1.2% at a supratherapeutic concentration of 100 microM. These results suggest that a carbamazepine-sensitive neurophysiological mechanism distinct from those responsible for epileptiform burst generation plays a key role in the generation of afterdischarges in developing hippocampus.

Animals↗
PubMed1987

Health and productivity of dairy cows fed polychlorinated biphenyls.

Holstein cows were studied through a complete lactation, a nonlactating period, and 42 days of a subsequent lactation for overt and subtle responses to a commercial mixture of polychlorinated biphenyls. Dosed cows (n = 4) received consecutive 60-day periods of daily dosing with 10, 100, and 1000 mg of Aroclor 1254. Control cows (n = 6) received daily sham doses. The following were recorded: daily milk production, feed intake, and health observations; weekly body weight, temperature, heart and respiratory rates and rectal palpation; semi-monthly clinical chemistry determinations; and monthly milk fat, microbiological culture of quarter foremilk samples, and composite milk somatic cell counts. Mean daily milk production (22.4 +/- 1.1 vs 24.8 +/- 1.0 kg) and net energy of a complete lactation (1.46 +/- 0.05 vs 1.45 +/- 0.03 Mcal/kg dry matter intake) were not different (p = 0.85) for control and PCB-dosed cows. Milk production during the first 42 days of the subsequent lactation was also similar for control and dosed cows. Occurrences of injuries, dysfunctions, and general infections were not related to polychlorinated biphenyl exposure. Intramammary infections were detected for both lactations with 51 and 32 infections detected in microbiological cultures, respectively, for the control and dosed groups. Environmental pathogens were most frequently isolated from cases of clinically apparent mastitis. The majority of quarter infections detected were due to Corynebacterium bovis. Only one animal (dosed, necropsy revealed left oviduct obstructed) failed to conceive with three to six services required before conception for the other control and dosed cows. Exposure to polychlorinated biphenyls resulting in maximal residues in milk fat, near 100 micrograms/g, had no apparent effect on health and productivity.

Animals↗
PubMed1986

Fluorometric quantitation of cellular and nonprotein thiols.

A microfluorometric assay for thiols has been developed using the thiol-specific fluorochrome N-[4-(7-diethylamino-4-methyl-3-coumarinyl)phenyl]maleimide (CPM). The technique may be used to quantitate either cellular or plasma thiols over a range of 0.01 to 3.0 nmol and may be used with as few as 1-3 X 10(5) cells giving highly proportional and reproducible results. Values for nonprotein thiols obtained with this assay agree well with previous reports on glutathione (GSH) levels for both lymphocytes and plasma. Readings are determined with the aid of an automated fluorescence microplate reader which allows up to 96 samples, including standards, to be read at the same time. Cellular thiols accessible after lysis were also quantitated before and after treatment of intact cells with various thiol-reactive chemicals. Interestingly, HgCl2, bromoethanesulfonic acid, and N-ethylmaleimide differentially modified protein and nonprotein thiol levels.

Animals↗
PubMed1986

Extracellular K+ accumulation during penicillin-induced epileptogenesis in the CA3 region of immature rat hippocampus.

Ion-selective microelectrode techniques were used to study extracellular K+ changes associated with penicillin-induced epileptogenesis in the CA3 region of hippocampal slices. Recordings were made in slices taken from rats 9-16 days of age, which have a pronounced capacity to undergo prolonged synchronized afterdischarges. Direct comparisons were made to slices from hippocampus from more mature rats, 30-35 days old, which are much less prone to seizure-like events. The amplitude and time course of the K+ transients varied across the CA3 laminae. K+ signals were largest close to stratum pyramidale in stratum oriens (the infrapyramidal zone). Recordings from this site showed extracellular K+ accumulation to be unusually large in immature hippocampus. The ceiling [K+]o level recorded during seizure-like events ranged from 14.4 to 20.2 mM and averaged 16.9 mM. The peak amplitude of extracellular K+ transients following an epileptiform burst in slices from immature rats averaged 4.31 mM while the mean of similar recordings from mature rats was 0.97 mM. Detailed laminar distribution studies in developing hippocampus revealed that the K+ signals were large in the proximal two-thirds of the basilar dendrites and proximal half of the apical dendrites. K+ accumulation in stratum pyramidale was comparatively small even though at its very edge in stratum oriens large K+ transients were always recorded. The latter was also true in recordings from mature hippocampus. Other dendritic signals in mature tissue were comparatively small. Laminar analysis was performed of the field potentials recorded by the reference barrel of the K+ electrodes. Negative field potential for the epileptiform burst and subsequent slow potential correlated in space with sites of K+ accumulation in both immature and mature hippocampal slices. Interictal and prolonged ictal-like discharges, recorded in developing hippocampus, arose from the same baseline [K+]o. However, since [K+]o is excessively high during the course of these epileptiform events it most likely has a role in the unusual propensity of immature hippocampus for seizures.

Age Factors↗