Biomedical subjects

L Kung

Publications and source records attributed to L Kung.

At least 37 records · Page 2Linked to original sources

PubMed2000

Microbial populations, fermentation end-products, and aerobic stability of corn silage treated with ammonia or a propionic acid-based preservative.

We studied the effects of ammonia treatment on microbial populations during the fermentation of corn silage. We also compared the effects of ammonia to a preservative containing buffered propionic acid and other antifungal compounds on the fermentation and aerobic stability of corn silage. In the first experiment, whole-plant corn was ensiled without treatment or treated with ammonia-N to supply an additional 0.3% N (fresh-forage basis). The addition of ammonia immediately increased silage pH and had no effect on numbers of lactic acid bacteria, but delayed their growth compared with untreated silage. Numbers of enterobacteria declined more slowly, but numbers of yeasts and molds declined more quickly in silage treated with ammonia. During the early stages of ensiling, lactic acid increased more rapidly in untreated than in treated silage. The reverse was true for acetic acid concentrations. When exposed to air, growth of yeasts and molds was delayed in ammonia-treated silage. In a second experiment, various levels (0.1 to 0.3%, fresh weight) of ammonium-N or a preservative with buffered propionic acid were added to whole-plant corn and allowed to ensile for 106 d. Silage treated with ammonia had a greater ratio of L- to D-lactic acid than did other silages. Untreated silage was aerobically stable for 32.3 h, whereas the low (42 h) and moderate (52.7 h) concentrations of both additives numerically improved aerobic stability. High concentrations of ammonia-N (0.3%) or a buffered propionic acid preservative (0.3%), markedly improved the aerobic stability of corn silage (82 and 69 h for ammonia and propionic acid-treated silage, respectively).

Ammonia↗

PubMed1999

The temporal profile of calcineurin inhibition by cyclosporine in vivo.

BACKGROUND: Cyclosporine (CsA) acts by inhibiting the phosphatase calcineurin (CN), but the time course and extent of inhibition in vivo are unknown. We examined the effect of single oral CsA doses on CN activity in humans and mice in vivo. METHODS: In humans, blood CsA levels were determined and CN activity was measured in whole blood and in blood leukocytes of patients up to 12 hr after CsA dosing (just before the second dose). Samples were collected from patients receiving a first single dose (2.5 mg/kg), and up to 14 days later after repeated dosing. In mice, after CsA dosing (12.5-200 mg/kg) by oral gavage, CsA levels in blood and tissue (spleen, kidney) were determined and CN activity was measured in spleen and kidney. RESULTS: In humans, peak CsA levels of 800-2285 microg/L at 1-2 hr produced 70-96% CN inhibition. Inhibition correlated closely with the rise and fall of CsA levels with no observable lag at the times sampled. Repeated doses showed similar CN inhibition to first dose, with no significant adaptation. In mice, CsA peaked at 1 hr in blood, spleen, and kidney, with higher concentrations in spleen and kidney than in blood. CN inhibition closely followed CsA concentrations/doses, and was greater in kidney than spleen. CONCLUSION: Thus CsA induces partial CN inhibition that varies directly with the blood and tissue levels, and may be greater in some tissues due to higher drug accumulation. The high CsA concentrations and CN inhibition in kidney may be relevant to nephrotoxicity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Mitochondrial pathology in human schizophrenic striatum: a postmortem ultrastructural study.

Studies using in vivo imaging or microscopic analysis of autopsy specimens indicate abnormalities in the striatum of schizophrenics including lower striatal metabolism, a change which can be normalized by antipsychotic medication. To investigate the possibility that abnormalities in schizophrenia brain may be due, in part, to pathology in mitochondria, organelles which generate energy, postmortem brain tissue from schizophrenic and control cases was obtained from the Maryland Brain Collection. Mitochondria in electron micrographs of striatal neuropil were counted and digitized. The caudate and the putamen of the schizophrenic subjects contained significantly (P < 0.05) fewer (a decrease of approximately 20%) mitochondrial profiles throughout the neuropil than did normal controls. The numbers of mitochondrial profiles per axon terminal appeared lower in the subset of schizophrenics off-drug as compared to either the subset of schizophrenics on-drug or to controls, suggesting that neuroleptic treatment may normalize this measure. The structural integrity of mitochondrial profiles in the schizophrenic striata was not obviously different from that of controls. Fewer mitochondrial profiles suggest decreased energy demands or diminished capacity to respond to energy requirements in the structures that contain them. These data are consistent with other studies showing decreased metabolism in the striatum of schizophrenics and may identify, in part, the anatomical basis of this deficit.

Analysis of Variance↗

PubMed1998

Immunocytochemical localization of tyrosine hydroxylase in the human striatum: a postmortem ultrastructural study.

An electron microscopic evaluation of tyrosine hydroxylase (TH) immunocytochemistry was used to describe the synaptic organization of dopamine innervation of the striatum in postmortem human brain tissue. TH immunoreactivity was qualitatively and quantitatively similar in the caudate and putamen. TH immunoreactivity was present mainly in unmyelinated axons and occasionally in myelinated axons. Both TH-immunoreactive (TH-i) varicosities (0.75-1.5 microm) and intervaricose segments (0.2-0.3 microm) formed synapses with spines and dendrites. Most synapses formed by TH-i profiles were symmetric axospinous (57-62%) or symmetric axodendritic (33-35%). An occasional asymmetric axodendritic or asymmetric axospinous synapse was observed. Approximately 35-50% of all symmetric axospinous and axodendritic synapses were formed by TH-i boutons. Synapses formed by TH-i profiles were short in length (0.226 microm) and had nonperforated postsynaptic densities. TH-i profiles formed synapses with both the head (40%) and the neck (60%) of spines. Typically, the TH-i bouton was apposed to both a spine and a nonlabeled terminal which formed an asymmetric synapse with that spine. Direct, nonsynaptic appositions were often seen between TH-labeled and nonlabeled boutons forming asymmetric synapses. The general pattern ofTH immunoreactivity was similar to that of other species except for the presence of TH-i myelinated axons and the observation that the majority of TH-i synapses were formed with spines rather than with dendritic shafts.

Adult↗

PubMed1998

Synaptic changes in the striatum of schizophrenic cases: a controlled postmortem ultrastructural study.

Although studies indicate abnormalities in the striatum of schizophrenic people, little information exists on the synaptic changes that may be present at the ultrastructural level. Autopsy specimens of striatal tissue from people with schizophrenia, normal controls, and psychiatric controls were obtained from the Maryland Brain Collection. Several abnormalities were noted in the schizophrenic group that were not present in the normal or psychiatric controls. In schizophrenic tissue, the density and/or proportion of symmetric synaptic profiles, particularly those ending on spines, were lower in the caudate vs. the putamen, implying an imbalance in inhibitory synaptic transmission between these two structures. The density of perforated synaptic profiles, cortical afferents thought to be involved in synaptic turnover and cognition, was lower in the striatum of the schizophrenic group compared to the control groups. The density of axodendritic synaptic profiles, particularly of the asymmetric type, was decreased in the caudate, but not the putamen, of a subset of schizophrenic cases that were nondyskinetic and off drugs (NDODS). The proportion of asymmetric axospinous synaptic profiles was elevated in the caudate of the NDODS cases in comparison to normal controls. The variety of synapses affected in the schizophrenic group implies the involvement of several neuronal circuits. The alterations observed in the schizophrenic striatum were usually due to changes in the caudate, but not the putamen, which argues against drug-related alterations. Since the striatum, particularly the caudate nucleus, is involved in cognition and emotion, these neuroanatomical changes could underlie, in part, aspects of schizophrenic psychopathology.

Adult↗

PubMed1998

Calcineurin and the biological effect of cyclosporine and tacrolimus.

The mechanism of the immunosuppressive effect of CyA and FK 506 can be monitored in vivo in humans. The picture emerging is of a close relationship between drug concentrations and CN inhibition. But many puzzles of the drugs remain. What is the role of CyA in the activation of transforming growth factor-beta (TGF-beta), particularly in relationship to nephrotoxicity and fibrogenesis? How important are the anti-inflammatory (non T) effects of CyA, and which cells do they operate in? Are there effects of CyA and FK 506 all attributable to CN inhibition, and how much of them are mediated through the NFATC family of transcription factors? Finally, it would be useful to know what the inhibitory effects of CyA are on tolerance and negative regulatory events.

Animals↗

PubMed1998

The effect of preservatives based on propionic acid on the fermentation and aerobic stability of corn silage and a total mixed ration.

For 3 successive yr, whole-plant corn was ensiled in laboratory silos with low percentages of silage preservatives, the primary active ingredient of which was propionic acid. Preservatives were added to forage just prior to ensiling at rates of 0.1 to 0.2% of the fresh forage weight. In all 3 yr, treatments had minor effects on fermentation end products, except that the concentration of propionic acid was greater because of its addition. The mean low and high percentages of preservatives increased aerobic stability of the treated silages by 19 and 57 h, respectively, in Experiment 1 and by 17 and 38 h, respectively, in Experiment 2. In Experiment 3, aerobic stability was improved by > 90 h by preservatives (0.2% addition). In a lactation study, a total mixed ration (46% dry matter) was mixed without or with (0.2 or 0.3%) a stabilizer that was designed to prevent spoilage in the feed bunk. The high dose resulted in orts with a lower pH and temperature after 24 h in the feed bunk. However, dry matter intake and milk production were unaffected by treatments. Chemical preservatives based on propionic acid added at low rates did not affect fermentation but were effective in the reduction of heating in corn silage and in a total mixed ration.

Aerobiosis↗

PubMed1998

Inhibition of sulfate reduction to sulfide by 9,10-anthraquinone in in vitro ruminal fermentations.

We studied the effects of sulfur and 9,10-anthraquinone on in vitro ruminal fermentation and production of hydrogen sulfide. A complete, pelleted diet containing 26.8% acid detergent fiber, 15.9% crude protein, and 0.25 to 0.29% sulfur was used as the basal substrate. Fermentations were conducted using the basal substrate and various sulfur additions (elemental sulfur, thiosulfate, calcium sulfate, and sodium sulfate) with or without varying amounts of 9,10-anthraquinone. An increase in the sulfur content of the substrate to > 1.0% with various sources of sulfur had minimal effects on concentrations of volatile fatty acids, but the production of hydrogen sulfide increased. High amounts of 9,10-anthraquinone (10 and 25 ppm of fluid) decreased the molar proportion of acetate and decreased the production of methane and hydrogen sulfide. However, 9,10-anthraquinone increased the molar proportions of propionate and butyrate. Approximately 70% of 9,10-anthraquinone was recovered after 24 h of in vitro ruminal fermentation. These findings suggest that 9,10-anthraquinone has the potential to reduce the production of methane and hydrogen sulfide in ruminal fermentations.

Ammonia↗

PubMed1997

Evidence that calcineurin is rate-limiting for primary human lymphocyte activation.

Cyclosporine (CsA) is both a clinical immunosuppressive drug and a probe to dissect intracellular signaling pathways. In vitro, CsA inhibits lymphocyte gene activation by inhibiting the phosphatase activity of calcineurin (CN). In clinical use, CsA treatment inhibits 50-75% of CN activity in circulating leukocytes. We modeled this degree of CN inhibition in primary human leukocytes in vitro in order to study the effect of partial CN inhibition on the downstream signaling events that lead to gene activation. In CsA-treated leukocytes stimulated by calcium ionophore, the degree of reduction in CN activity was accompanied by a similar degree of inhibition of each event tested: dephosphorylation of nuclear factor of activated T cell proteins, nuclear DNA binding, activation of a transfected reporter gene construct, IFN-gamma and IL-2 mRNA accumulation, and IFN-gamma production. Furthermore, the degree of CN inhibition was reflected by a similar degree of reduction in lymphocyte proliferation and IFN-gamma production in the allogeneic mixed lymphocyte cultures. These data support the conclusion that CN activity is rate-limiting for the activation of primary human T lymphocytes. Thus, the reduction of CN activity observed in CsA-treated patients is accompanied by a similar degree of reduction in lymphocyte gene activation, and accounts for the immunosuppression observed.

Calcimycin↗

PubMed1997

Effects of a live yeast culture and enzymes on in vitro ruminal fermentation and milk production of dairy cows.

Live yeast culture (Saccharomyces cerevisiae) grew best on malt extract agar and required incubation under aerobic conditions to maximize the number of viable cells. In sterile, anaerobic ruminal fluid that had been supplemented with malt extract, yeast cells remained viable and metabolically active for up to 48 h, as indicated by the production of ethanol. A supplement containing live yeast and enzymes was fed twice daily with a diet of 50:50 (wt/wt) forage to concentrate (dry matter basis) to continuous fermentors inoculated with mixed ruminal microorganisms. The supplement had no effect on major fermentation acids or pH. After the last supplement with yeast was fed, numbers of yeast immediately decreased in the fermentors and were not detectable after 24 h. In the first of two lactation experiments, Holstein cows in midlactation were offered a diet with corn silage as the primary forage source. Half of the cows received a top-dressing based on corn that contained 10 g/d of the yeast and enzyme supplement. The supplement had no effect on milk production, milk composition, or dry matter intake. In a second lactation experiment, high producing cows in early lactation were fed 0, 10, and 20 g/d of the supplement. Cows fed the control diet produced 36.4 kg of milk/d, and milk production was 39.3 and 38.0 kg/d from cows fed 10 and 20 g of yeast/d, respectively.

Animal Feed↗

PubMed1997

An evaluation of two management systems for rearing calves fed milk replacer.

In two experiments, 54 dairy calves were allotted to one of two management systems. One-half of the calves was raised under a conventional system that consisted of housing in separate calf hutches and manually feeding milk replacer twice daily until weaning at 7 to 8 wk of age. In this system, calves had ad libitum access to a starter diet. The remainder of the calves was housed in a single group pen and was fed via a computerized system that allowed controlled access to milk replacer and starter for 24 h/d. In both experiments, average daily gain and final body weight at weaning were similar between management systems. In Experiment 2, calves that were fed milk replacer via the automated system consumed more starter diet during the 2nd and 3rd wk, but consumed less starter during wk 6 and 7; however, total consumption of the starter diet prior to weaning was not different between treatments. Calves in the group pen had fewer days of medication than did those in hutches. The time needed to manage a calf in a hutch amounted to approximately 10 min per calf, but the time committed to management of a calf raised in the group pen was < 1 min/d. A 200-cow dairy herd with a 35% yearly cull rate and a mean calf mortality rate of 10% would regain costs of initial investment for the computer feeder by savings in labor within 2 to 3 yr.

Animal Feed↗

PubMed1996

Characterization of 5'AMP-activated protein kinase activity in the heart and its role in inhibiting acetyl-CoA carboxylase during reperfusion following ischemia.

Despite the high expression of 5'AMP activated protein kinase (AMPK) in heart, the activity and function of this enzyme in heart muscle has not been characterized. We demonstrate that rat hearts have a high AMPK activity, comparable to that found in liver, which could be stimulated up to 3-fold by 5'AMP. Cardiac AMPK is also under phosphorylation control, since in vitro incubation of cardiac AMPK with protein phosphatase 2A completely abolished activity, while incubation with ATP/Mg(2+) resulted in over a 2-fold increase in activity. To investigate the function of AMPK in heart muscle, isolated working rat hearts were subjected to 30 min of global no-flow ischemia, followed by 60 min of aerobic reperfusion. AMPK activity was increased in heart at the end of reperfusion compared to aerobic controls (379 +/- 53 (n=5) vs. 139 +/- 19 (n=5) pmol x min(-1) x mg protein(-1), P<0.05, respectively). Treatment of AMPK in vitro with protein phosphatase 2A reversed this activation. Since AMPK can phosphorylate and inactivate acetyl-CoA carboxylase (ACC) in other tissues, and heart ACC has an important role in regulating fatty acid oxidation, we measured ACC activity in hearts reperfused post-ischemia. ACC activity was decreased at the end of reperfusion compared to aerobic controls (3.64 +/- 0.36 (n=9) vs. 10.93 +/- 0.60 (n=11) nmol x min(-1) x mg protein(-1), respectively, P<0.05). A significant negative correlation (r= -0.78) was observed between AMPK activity and ACC activity measured in aerobic and reperfused ischemic hearts. Low ACC activity could be reversed if ACC was extracted from hearts in the absence of phosphatase inhibitors, suggesting that phosphorylation of ACC decreased enzyme activity. This suggests that following ischemia AMPK is phosphorylated and activated (possibly by an AMPK kinase). AMPK then phosphorylates and inactivates ACC. The resultant decrease in malonyl-CoA levels could explain the acceleration of fatty acid oxidation that is observed during reperfusion of ischemic hearts.

AMP-Activated Protein Kinases↗

PubMed1996

Reduced striatal spine size in schizophrenia: a postmortem ultrastructural study.

Numerous studies using in vivo imaging or light microscopic analysis of autopsy specimens have found abnormalities in the striatum of schizophrenics. Striatal tissue from the Maryland Brain Collection with short postmortem intervals was used in the present study. Electron micrographs of striatal neuropil were digitized to determine the area of dendritic spines. Spines were similar in size in both the caudate and the putamen in normal individuals. The spines in tissue from schizophrenics were also similar in size between these two regions. However, striatal spines in schizophrenics were approximately 30% smaller than in controls (p < 0.05). Since the majority of synapses in the striatum are formed with spines, this change in the schizophrenic brain may represent aberrant synaptic conductance and/or efficacy.

Autopsy↗

PubMed1996

In vitro inhibition of microbial methane production by 9,10-anthraquinone.

Monensin, 2,2-dichloroacetamide, and 9,10-anthraquinone were incubated for 24 h in ruminal fluid and buffer with 100:0, 50:50, and 10:90 forage-concentrate diets. Monensin (.5 ppm of the fluid) increased (P < .05) the molar proportion of propionate in the 50 and 100% forage diets but not in the high concentrate diet. At the same level of addition, 2,2-dichloroacetamide increased (P < .05) the molar proportion of propionate only in the 50:50 forage-concentrate diet. Relative to control cultures, monensin and 2,2-dichloroacetamide numerically decreased methane production in the 10 and 100% forage diets and decreased (P < .05) methane in the 50% forage diet. Hydrogen production was unaffected by treatment. Lack of an effect on fermentation end products in the high concentrate diet was probably a result of the low dose levels. In general, increasing levels of 9,10-anthraquinone (.5, 1.0, and 5.0 ppm) reduced total VFA concentration and the molar proportion of acetate, and increased propionate, butyrate and valerate. Increasing levels of 9,10-anthraquinone caused linear and quadratic decreases (P < .05) in methane production, and increases (P < .05) in hydrogen. There were no consistent effects on ammonia concentration in culture fluid from any of the compounds. In continuous culture of a 10:90 forage-concentrate diet, addition of 9,10-anthraquinone (10 ppm of the fluid/12 h) caused changes similar to those observed in batch culture with the exception of a decreased (P < .05) molar percentage of propionate, which may have been due to the high dose. The data are interpreted to indicate that 9,10-anthraquinone has the ability to alter in vitro microbial fermentation.

Acetamides↗

PubMed1996

An enzyme additive for corn silage: effects on silage composition and animal performance.

Whole-plant corn was harvested at the soft dough stage of maturity, was left untreated or was treated with an enzyme additive containing cellulase and hemicellulase, and was ensiled in bag or mini silos. Silage fermentation was not markedly altered by treatment, regardless of silo type; however, enzyme treatment reduced NDF and ADF contents of silage and reduced in vitro NDF digestibility after 196 d of storage in mini silos. For corn silage stored in bag silos, enzyme treatment had no effect on fibrous components; however, for ruminal continuous cultures, a diet containing treated silage decreased the acetate to propionate ratio. Nutrient digestion was not different in lambs fed untreated or treated corn silage, but N retention was greater in lambs fed the latter. Treatment of corn silage with the enzyme additive had no effect on DMI, milk production, milk composition, or feed efficiency when silage was fed at 43% (DM basis) of the total mixed diet of the dairy cows. Enzyme treatment had minimal effects on silage fermentation, inconsistent effects on fibrous components of silage, and improved N retention in lambs but had no effect on production of dairy cows.

Animal Nutritional Physiological Phenomena↗

PubMed1996

Effects of an enzyme additive on composition of corn silage ensiled at various stages of maturity.

Corn forage at the milk, soft dough, and black layer stages of maturity (22, 28, and 44% DM, respectively) was treated with an enzyme additive at 1, 10, or 100 times the recommended dose and ensiled in laboratory silos at 26 degrees C. By in vitro assay, the additive contained a full complement of cellulase and hemicellulase activities. The pH and temperature optima for cellulase and hemicellulase activities were 4.8 and 50 degrees C, respectively. Regardless of dose, the additive had no effect on fermentation acids or nitrogenous compounds in silage at any maturity; however, high doses increased the glucose content of silage at the milk stage of maturity and increased ethanol content at the soft dough stage. Across maturities, addition of the enzyme additive resulted in a linear decrease in ADF, NDF, and hemicellulose content of corn silage but decreased the acid detergent lignin content of silage only at the milk and black layer stages of maturity. The enzyme additive had no consistent effect on in vitro NDF digestion.

Cellulase↗

PubMed1995

Differential activity of trans-acting hammerhead ribozymes targeted to beta amyloid peptide precursor mRNA by altering the symmetry of helices I and III.

In order to determine whether distributing the pairing bases in helices I and III of a hammerhead ribozyme asymmetrically would enhance the cleavage of trans-acting ribozymes designed to degrade cellular mRNAs, we measured the cleavage properties of symmetric and asymmetric ribozymes targeted to the amyloid peptide precursor (beta APP) mRNA. Five ribozymes were formed from three beta APP synthetic mRNA analogs and two ribozyme RNA core sequences. Symmetric ribozymes beta 133/Rz133 and beta 125/Rz133 contained 8 bp in helix I and 7 bp in helix III. Asymmetric ribozyme beta 125/Rz125 had 13 bp in helix I and 4 bp in helix III, asymmetric ribozyme beta 123/Rz125 had 11 bp in helix I and 4 bp in helix III, while asymmetric ribozyme beta 133/Rz125 contained 8 bp in helix I and 4 bp in helix III. The ability of each ribozyme to cleave its substrate RNA was first assessed under single-turnover conditions at 37 degrees C. These studies revealed that only symmetric ribozyme, beta 133/Rz133, and asymmetric ribozyme beta 123/Rz125 effectively cleaved their substrates. Further studies using a 80 degrees C, 1-min-->37 degrees C, 1-min temperature cycling paradigm were performed to increase the cleavage efficiency of the ribozymes. Under these conditions ribozymes beta 133/Rz133, beta 125/Rz125, and beta 123/Rz125 were kinetically well behaved. Therefore, the fact that the symmetric ribozyme beta 133/Rz133 was more active than its asymmetric counterparts indicates that symmetrically distributing the pairing bases in helices I and III around this cleavage site is preferred.

Amyloid↗

PubMed1995

Preventing in vitro lactate accumulation in ruminal fermentations by inoculation with Megasphaera elsdenii.

In vitro fermentations containing a mixed culture of ruminal bacteria (ruminal fluid from a hay-fed steer), buffer, and primarily rapidly degradable substrates (starch, glucose, cellulose, cellobiose, and trypticase) were inoculated with an overnight culture of Megasphaera elsdenii B159. Triplicate flasks were either uninoculated or inoculated to obtain a final concentration of 8.7 x 10(5) and 8.7 x 10(6) colony forming units of M. elsdenii per milliliter of culture fluid. Inoculation with M. elsdenii prevented an accumulation of lactic acid and excessive drop in pH. Lactate peaked at more than 40 mM in untreated cultures. In cultures inoculated with a low dose of M. elsdenii, lactate concentration peaked at approximately 25 mM at 5 h of fermentation but decreased rapidly to less than 5 mM by 7 h of fermentation. With the addition of the high dose of M. elsdenii, lactate was never greater than 2 mM (P < .05) throughout fermentation. Cultures treated with M. elsdenii had greater amounts (P < .05) of isobutyrate, butyrate, isovalerate, and valerate than untreated cultures. After 24 h of fermentation, one-half of the culture fluid was transferred to an equal volume of fresh buffer with substrate but was not inoculated with further quantities of M. elsdenii. Six hours after transfer, cultures that had been originally treated with M. elsdenii had lower (P < .05) amounts of lactate than untreated cultures. Inoculation with M. elsdenii has potential to prevent lactate accumulation in diets containing readily fermentable carbohydrates.

Animals↗