The determination of l-carnitine in several food samples

We designed this study to re-validate some methodological parameters of the radio-enzymatic assay, including phenomena of residual, non-carnitine radioactivity present in some assay mixtures of food samples. The second part of the paper presents l-carnitine concentrations (total-, free- and acyl-carnitine) in a wide range of food samples of animal and plant origin.     

Synthesis of ruminal microbial protein and volatile fatty acid production in vitro

Growth of a mixed ruminal population taken from a sheep on a protein-free (all urea) purified diet was estimated by an in vitro fermentation technique including precipitation of microbial protein by trichloracetic acid. Volatile fatty acid production in vitro was determined, and the associated a denosine triphosphate was estimated as moles volatile fatty acids X 2.4. On this basis, the quantity of microbial protein synthesized per mole of adenosine triphosphate increased at higher microbial growth rates.     

Embedded Sensors in Rubber and Other Polymer Components

Abstract: Many polymer components are susceptible to catastrophic failure or are critical to the performance of the products they comprise. Because of this, the capability to monitor structural failures or performance reduction in these components is beneficial. It is difficult to fabricate sensors for polymer components because they often have complex shapes or are assembled in isolated locations. To solve this problem, micro‐scale electronic sensors, embedded within polymer components, were developed at Purdue University. Conductive polymer materials were used as the primary sensing element in the sensors. Testing results reveal that embedded sensors in polymer components can successfully indicate significant signal changes more than 100 loading cycles prior to catastrophic failure. Multiple sensing methods and applications have been tested and more are being researched. These findings may open doors for future polymer sensors that can improve safety and provide useful measurements for polymer components.     

Hypocalcemia reduces endogenous glucose production in hyperketonemic sheep

In previous experiments it has been shown that hyperketonemia lowered plasma glucose concentration in sheep and depressed endogenous glucose production by approximately 30%. This facilitates the onset of pregnancy toxemia. In the last trimester of gestation, hyperketonemia in sheep is often associated with hypocalcemia. There is an indication that hypocalcemia exerts an additional depressive effect on endogenous glucose production. The present study was undertaken to examine the effect in sheep of hypocalcemia on endogenous glucose production in the presence of normo- and hyperketonemia. The experiments were carried out with seven multiparous sheep during three different reproductive states, i.e., during pregnancy (10 +/- 8 d prepartum), during lactation (21 +/- 8 d postpartum), and 4 wk after weaning of the lambs. Concentration of glucose in plasma, turnover of glucose and the rate constant of glucose turnover were measured by isotope dilution during normo- and hypocalcemia and in the presence of normal and elevated beta-hydroxybutyrate (BHB) concentrations. Hypocalcemia was induced by i.v. infusions of Na2EDTA. Hyperketonemia was maintained by i.v. infusion of DL-beta-hydroxybutyrate. The experiments showed that induction of hypocalcemia: 1) induced a decline in plasma glucose concentration in all reproductive states during normo- and hyperketonemia and 2) significantly lowered endogenous production of glucose in nonpregnant hyperketonemic and in lactating normoketonemic ewes. Pregnant normoketonemic ewes were able to compensate for the hypoglycemic effect of hypocalcemia and to keep endogenous production at the normocalcemic level. We concluded that hypocalcemia does not promote the onset of pregnancy toxemia per se but will facilitate the development of the disease when it is present in combination with hyperketonemia.     

Hyperketonemia impairs glucose metabolism in pregnant and nonpregnant ewes

The present study was undertaken to test the hypothesis that high ketone body concentrations suppress endogenous production of glucose and in pregnant sheep facilitate development of pregnancy toxemia. Rates of endogenous glucose production [mmol.min(-1)], and rate constants of glucose turnover [min(-1)] were measured in seven 12-h fasted sheep in the presence of normo- and hyperketonemia by use of D-2-[(3)H]-glucose. The measurements were carried out in the same sheep during the nonpregnant nonlactating state, during late pregnancy (10 +/- 7 d antepartum) and during lactation (19 +/- 6 d postpartum). Hyperketonemia (5 to 7 mmol.L(-1)), similar to that present in spontaneous ovine pregnancy toxemia, was induced by continuous intravenous 4-h infusions of DL-beta-hydroxybutyrate (DL-BHB). Glucose turnover [mmol.min(-1)] in the same 7 nonpregnant nonlactating, late pregnant, and lactating sheep was significantly greater during normoketonemia (0.80, 1.16, 1.76) than during hyperketonemia (0.66, 0.92, 1.16, respectively). The rate constants of glucose turnover were not altered by elevation of the BHB concentration. The results demonstrated that high BHB concentrations significantly suppressed endogenous glucose production but showed no effect on glucose utilization. The suppressive effect of hyperketonemia on hepatic glucose production resulted in a significant reduction of plasma glucose concentration and was qualitatively the same in all three reproductive states. The results indicate that hyperketonemia, which is regularly present in late twin pregnant hypoglycemic sheep contributes significantly to the reduction of available glucose. This effect of hyperketonemia may invoke sustained hypoglycemia and may render the ewe into a vicious cycle that probably makes the animal refractory to treatment in most cases.     

Renal and hepatic 1 alpha-hydroxylation of 25-hydroxyvitamin D3 in piglets suffering from pseudo vitamin D-deficiency rickets, type I

Research has shown that speech articulated in a clear manner is easier to understand than conversationally spoken speech in both the auditory-only (A-only) and auditory-visual (AV) domains. Because this research has been conducted using younger adults, it is unknown whether age-related changes in auditory and/or visual processing affect older adults' ability to benefit when a talker speaks clearly. The present study examined how speaking mode (clear vs conversational) and presentation mode (A-only vs AV) influenced nonsense sentence recognition by older listeners. Results showed that neither age nor hearing loss limited the amount of benefit that older adults obtained from a talker speaking clearly. However, age was inversely correlated with identification of AV (but not A-only) conversational speech, even when pure-tone thresholds were controlled statistically.     

Effect of insulin on glucose and and fat metabolism in ewes during various reproductive states in normal and hypocalcemia

Metabolic indicators of glucose and lipid metabolism, i.e. glucose turnover, insulin concentration in plasma, insulin clearance, concentrations of non-esterified fatty acids (NEFA), glycerol and potassium were investigated in nine ewes during three reproductive states in order to examine their importance for development of subclinical ketosis. The increase of insulin in plasma was measured after a continuous 60 min intravenous infusion of glucose (4.9 mmol.min-1). Turnover of glucose and insulin clearance were quantified during a combined euglycemic, hyperinsulinemic clamp. Insulin was consecutively infused in doses of 5 and 10 mU.kg-1.min-1 for about 2 1/2 hours, each. Plasma glucose concentration was adjusted to 5.3 to 5.8 mmol.l-1. The experiments were carried out during non-pregnancy and non-lactation, 4 weeks to 3 days before lambing and 3 to 4 weeks after lambing, each during normo- and hypocalcemia. Hypocalcemia (0.9 to 1.0 mmol Ca2+.l-1) was induced by continuous i.v. infusion of a 5% Na-EDTA solution. Infusion rate was continuously adjusted. The glucose induced increase in plasma insulin concentration was significantly lower during late pregnancy compared to peak lactation and non-pregnancy (46.3, 62.4 and 128 mU.l-1, respectively). The insulin clearance during a hyperinsulinemic clamp with 5 mU.kg-1.min-1 was significantly less during late pregnancy compared to peak lactation and non-pregnancy (3.7, 6.0, 4.8 ml.kg-1.min-1, respectively). The concentrations of NEFA and glycerol in plasma during the infusion of 5 mU insulin.kg-1.min-1 were significantly higher during late pregnancy than during non-pregnancy (NEFA: 0.41, 0.04 mmol.l-1; glycerol: 96, 29 mumol.l-1, respectively). The results showed that insulin responsiveness was significantly reduced in sheep during late pregnancy. The insulin-mediated uptake of glucose by muscle and fat tissues and the insulin-mediated inhibition of lipolysis were significantly reduced during late pregnancy compared to non-pregnancy and lactation. The diminished responsiveness of target tissue towards insulin during late pregnancy predisposed the animals for development of subclinical ketosis. Hypocalcemia exaggerated this situation by its inhibitory effect on hepatic gluconeogenesis and by enhancing insulin resistance of target tissues. The factors which are responsible for the altered responsiveness of target tissues towards insulin during late pregnancy are yet unknown. The potassium concentration in plasma showed a proportional increase with increase of the energy deficit of the target tissues. This effect could have been exerted by a decrease in cellular concentration of ATP and a concomitant reduction of the activity of Na(+)-K(+)-ATPase. The indicators of glucose and lipid metabolism which were examined in this study showed marked individual variation, particularly during late pregnancy. The marked changes of these indicators with reproductive stages as well as their great variation between individual sheep support the assumption that they are of significance for the development of pregnancy toxemia in sheep.     

Energetically consistent simulation of simultaneous impacts and contacts in multibody systems with friction

This paper presents a methodology for treating energy consistency when considering simultaneous impacts and contacts with friction in the simulation of systems of interconnected bodies. Hard impact and contact is considered where deformation of the impacting surfaces is negligible. The proposed approach uses a discrete algebraic model of impact in conjunction with moment and tangential coefficients of restitution (CORs) to develop a general impact law for determining post-impact velocities. This process depends on impulse–momentum theory, the complementarity conditions, a principle of maximum dissipation, and the determination of contact forces and post-impact accelerations. The proposed methodology also uses an energy-modifying COR to directly control the system’s energy profile over time. The key result is that different energy profiles yield different results and thus energy consistency should be considered carefully in the development of dynamic simulations. The approach is illustrated on a double pendulum, considered to be a benchmark case, and a bicycle structure.     

Generation of monoclonal antibodies against human prion proteins in PrP0/0 mice

BACKGROUND: Prion diseases belong to a group of neurodegenerative disorders affecting humans and animals. The human diseases include kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Str?ussler-Scheinker syndrome (GSS), and fatal familial insomnia (FFI). The pathogenic mechanisms of the prion diseases are not yet understood. Monoclonal antibodies provide valuable tools in the diagnosis, as well as in the basic research, of several diseases; however, monospecific antisera or monoclonal antibodies (mAbs) against human prion proteins were, until now, not available. MATERIALS AND METHODS: We have developed an immunization protocol based on nucleic acid injection into nontolerant PrP0/0 mice. DNA or RNA coding for different human prion proteins including the mutated sequences associated with CJD, GSS, and FFI were injected into muscle tissue. Mice were primarily inoculated with DNA plasmids encoding the prion protein (PRNP) gene and boosted either with DNA, RNA, or recombinant Semliki Forest Virus particles expressing PRNP. Hybridomas were then prepared. RESULTS: Different mAbs against human prion proteins were obtained, and their binding behavior was analyzed by peptide enzyme-linked immunosorbent assay, Western blot, immunofluorescence, and immunoprecipitation. Their cross-reactivity with prion protein from other species was also determined. Our mAbs are directed against four different linear epitopes and may also recognize discontinuous regions of the native prion protein. CONCLUSIONS: These antibodies should allow us to address questions concerning the nature of the prion protein as well as the initiation and progression of prion diseases. Moreover, these mAbs can now be used for the diagnosis of prion diseases of humans and animals.