Brain 3-methyoxytyramine varies inversely with blood glucose in decapitated rats

Concentrations of the dopamine metabolite, 3-methyoxytyramine, were decreased significantly in the corpus striatum and nucleus accumbens of rats 30 min after the IP injection of D-glucose (2 g/kg). Conversely, 90 min after the administration of regular insulin (6 U/kg), significant increases in the concentrations of 3-methoxytyramine were observed in these two brain regions. Brain levels of the major metabolites of dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid, did not correlate well with blood glucose concentration. The significant negative correlation of blood glucose with striatal and accumbens 3-methoxytyramine suggests an inverse relationship between dopamine metabolism and blood glucose concentration, that may be secondary to decapitation-induced anoxia.

Insulin and acivicin improve host nutrition and prevent tumor growth during total parenteral nutrition

The effect that a 14-day treatment program of total parenteral nutrition (TPN) combined with the glutamine antimetabolite, acivicin, and anabolic hormone, insulin, has on carcass weight and muscle sparing was investigated in tumor-bearing rats. Although TPN resulted in increased carcass weight gain as compared to chow-fed tumor-bearing rats, no savings in gastrocnemius muscle could be demonstrated. The combination of TPN with daily insulin treatment elicited significant increases in both carcass weight and muscle savings, with no alteration in tumor growth. Although combining acivicin with TPN halted tumor growth and increased carcass weight, the change in carcass weight was less than that observed with the insulin-TPN combination. No muscle savings were observed in the acivicin-TPN-treated rats. Yet when acivicin and insulin were combined with TPN, tumor growth was stopped, carcass weight was gained, and muscle mass was saved. Therefore, these experiments suggest that it is possible to add lean body tissue and stabilize tumor growth in rats that receive TPN through anabolic hormone treatment combined with an inhibitor of tumor metabolism.

Reduction of tumor growth following treatment with a glutamine antimetabolite

Assessment of arterial-venous differences across transplanted methylcholanthrene-induced sarcomas in rats revealed significant decreases in plasma concentrations of glutamine, serine and glucose. Treatment with the glutamine antimetabolite, acivicin, significantly reduced tumor weights by 65% at the conclusion of the experiment 34 days after tumor induction. These results suggest that glutamine is an essential metabolic substrate for tumor growth and that blockade of glutamine utilization can inhibit the growth of these transplantable sarcomas.

Reversal of neurochemical aberrations after tumor resection in rats

Assessment of biochemical parameters in methylcholanthrene sarcoma-bearing rats 2 days after the onset of anorexia revealed several biochemical aberrations in blood and brain. Plasma levels of glucose were decreased and lactate concentrations were increased. The plasma and brain amino acid profiles were also greatly altered in these rats, characterized by increased brain concentrations of glutamine and large neutral amino acids. Analysis of regional neurotransmitter and metabolite levels by high-performance liquid chromatography suggested increases in the neuronal activity of dopamine and serotonin in each brain region examined. Surgical removal of the tumors in another group of anorectic tumor-bearing rats was followed by the return of normal feeding within 6 days. Associated with the normalization of food intake was the reversal of these biochemical aberrations in blood and brain. It is hypothesized that the utilization of glutamine and excretion of ammonia by tumor tissue is the precursor of these alterations in brain amino acids and neurotransmitters, which may be causing anorexia.

Hyperammonemia in anorectic tumor-bearing rats

Plasma ammonia concentrations were significantly elevated by 150% in anorectic rats bearing methylcholanthrene sarcomas. Assessment of ammonia levels in blood draining these sarcomas indicated nearly a 20-fold increase as compared with venous blood in control rats, suggesting the tumor mass as the source of this increase in ammonia. Infusing increasing concentrations of ammonium salts produced anorexia and alterations in brain amino acids in normal rats that were similar to those observed in anorectic tumor-bearing rats. Therefore, these results suggest that ammonia released by tumor tissue may be an important factor in the etiology of cancer anorexia.

Acivicin reduces tumor growth during total parenteral nutrition (TPN)

Glutamine appears to be an important substrate for tumor growth. Since tumor growth rate may be stimulated by total parenteral nutrition (TPN), we investigated the effect of the glutamine antimetabolite, acivicin, on methylcholanthrene sarcoma growth in rats maintained on TPN or on rat chow. Acivicin treatment significantly reduced tumor growth by 67% in rats receiving TPN and by 71% in rats maintained on chow. Carcass weights were significantly increased by TPN in both acivicin-treated and saline solution-treated tumor-bearing rats. Tumor-carcass ratios were significantly decreased in both groups of acivicin-treated tumor-bearing rats. Acivicin treatment or a similar approach may therefore be useful for stabilizing tumor growth in patients receiving TPN.

A method for gene disruption that allows repeated use of URA3 selection in the construction of multiply disrupted yeast strains

In this paper, we describe a 3.8-kb molecular construct that we have used to disrupt yeast genes. The construct consists of a functional yeast URA3 gene flanked by 1.1-kb direct repeats of a bacterial sequence. It is straightforward to insert the 3.8-kb segment into a cloned target gene of interest and then introduce the resulting disruption into the yeast genome by integrative transformation. An appropriate DNA fragment containing the disruption plus flanking homology can be obtained by restriction enzyme digestion. After introducing such fragments into yeast by transformation, stable integrants can be isolated by selection for Ura+. The important feature of this construct that makes it especially useful is that recombination between the flanking direct repeats occurs at a high frequency (10(-4)) in vegetatively grown cultures. After excision, only one copy of the repeat sequence remains behind. Thus in the resulting strain, the Ura+ selection can be used again, either to disrupt a second gene in similar fashion or for another purpose.

Zinc-induced seizures: a new experimental model of epilepsy

Seizures produced by intracerebral injection of zinc sulfate in rabbits are a new chronic model of experimental epilepsy. The main features of this model are: the animals are easily controlled, the electrocorticogram is conveniently recorded, the endpoints are definite, and the rate of seizure is higher than with other methods. The commonly used antiepileptic drugs, such as phenobarbital (30 mg/kg), diphenylhydantoin (30 mg/kg), nitrazepam (3 mg/kg), and sodium valproate (300 mg/kg), have therapeutic effects in treating this experimental epilepsy, when they are given intravenously. But they can not protect the rabbits from death, except phenobarbital.