Determinants of urea nitrogen production in sepsis. Muscle catabolism, total parenteral nutrition, and hepatic clearance of amino acids

The major determinants of urea production were investigated in 26 patients with multiple trauma (300 studies). The body clearances (CLRs) of ten amino acids (AAs) were estimated as a ratio of muscle-released AAs plus total parenteral nutrition-infused AAs to their extracellular pool. While clinically septic trauma (ST) patients without multiple-organ failure syndrome (MOFS) had a higher level of urea nitrogen production (25.6 +/- 13.4 g of N per day) compared with nonseptic trauma (NST) patients (14 +/- 7.5 g of N per day) and with ST patients with MOFS (4.28 +/- 1.5 g of N per day), in all groups urea N production was found to be a function of muscle protein degradation (catabolism), total parenteral nutrition-administered AAs, and the ratio between leucine CLR and tyrosine CLR (L/T) (r2 = .82, P less than .0001). Since tyrosine is cleared almost exclusively by the liver, the L/T ratio may be regarded as an index of hepatic function. The significant differences between urea N production in ST and NST patients lay in an increased positive dependence on muscle catabolism and increased negative correlation with L/T in the ST group. At any L/T ratio, urea N production was increased in ST patients over NST patients, but in ST patients with MOFS, it fell to or below levels of NST patients. These data show that the ST process is associated with enhancement of ureagenesis, due to increased hepatic CLR of both exogenous and endogenous AAs. In sepsis with MOFS, a marked inhibition of urea synthesis occurs, partially explained by a decreased hepatic CLR of non-branched-chain AAs.     

Fluctuating dental asymmetry as an indicator of the stressful prenatal effects of delta9-tetrahydrocannabinol in the laboratory rat

Different groups of pregnant laboratory rats were given oral doses of Δ⁹-tetrahydrocannabinol (THC) (5 or 20 mg/kg) or its vehicle (propyleneglycol). Additional nondosed groups were pair-fed with the high-dose group or were allowed continuous access to food. A previously tested technique was used to assess the stressful effects on the offspring. Increased fluctuating dental asymmetry was found in the mandibular dentition of the offspring of THC treated animals. As the experimental design was controlled for route of administration, drug vehicle, and drug-induced dietary variation, we concluded that THC was stressful. An alternative to placental transfer, behavioral stress is a possible explanation for this effect.     

Plasma catecholamine and cardiovascular responses following hypothalamic stimulation in the awake cat

Ninety-three hypothalamic sites were electrically stimulated, using constant parameters, in awake, restrained cats to determine those regions which maximally activated the sympatho-adrenal (SA) and cardiovascular (CV) systems. Plasma catecholamine levels were measured over time following hypothalamic stimulation; levels of norepinephrine (NE) and epinephrine (E) served as indices of adrenergic neural and adrenal medullary activities, respectively. CV parameters of heart rate (HR) and mean intra-arterial blood pressure (MAP) were continuously monitored. The greatest elevation in plasma catecholamines was elicited by stimulation of sites in the perifornical area, ventromedial nucleus, and medial forebrain bundle. Several sites were identified which preferentially elevated one of the sympatho-adrenal neurotransmitters. A differential increase in plasma E was most frequently obtained from sites around the border of the ventromedial nucleus and in the medial forebrain bundle. Differential elevation of plasma NE was observed following stimulation of sites in the anterior commissure, central preoptic area, and dorsal perifornical region posterior to the ventromedial nucleus. Sites which activated the CV and SA systems were not always coincident; those sites which activated the CV system alone tended to be located in the lateral hypothalamus.     

Reticular formation neurons related to tongue movement in the behaving cat

We have found a number of cells related to tongue movement in the medial brain stem reticular formation of the unanesthetized cat. These cells constituted less than 2% of the cells tested in this region and were distributed throughout several nuclei in the medulla and pons including nucleus reticularis pontis caudalis, nucleus reticularis gigantocellularis, and the border between nucleus reticularis paramedianus and nucleus interfascicularis hypoglossi. All observed tongue movement cells (N = 6) fired maximally during protrusive tongue movements. One medullary cell discharged primarily during the protrusive tongue movement to the ipsilateral side, whereas no lateral preference was detected in the other cells. Gustatory and mechanosensory stimulation of the tongue was unnecessary for inducing discharge in these cells. Tongue movement-related cells shared several characteristics that differentiated them from adjacent reticular formation cells, including absence of response to startle-inducing auditory stimuli and low levels of spontaneous waking and sleep activity. In two pontine cells located near the trigeminal motor nucleus, spike-triggered averages of tongue EMG revealed a short-latency (5 ms) inhibitory effect on the ipsilateral genioglossus muscle by the units' discharge. We suggest that neurons of this type might be involved in tongue-jaw coordination during mastication, licking, and grooming.