Search PubMed⌕ Search

Biomedical subjects

A M Landel

Publications and source records attributed to A M Landel.

9 recordsLinked to original sources
PubMed1987

Observations on predicted brain influx rates of neurotransmitter precursors. Effects of tumor, operative stress with tumor removal, and postoperative TPN of varying amino acid compositions.

Effects of tumor, operative stress and tumor removal, and postoperative TPN of varying amino acid compositions on brain levels of tryptophan or tyrosine as predicted by their brain influx rates were studied in normals and in malnourished cancer patients. Concentrations of the large neutral amino acids (LNAA) were determined in patients before and after tumor removal, and in postoperative patients before and after receiving either a standard TPN solution (STD-TPN), or a branched-chain amino acid solution (BCAA-TPN). The LNAA were altered in all groups versus normals. Brain influx rates showed the following: in preoperative patients, predicted brain tryptophan levels were below normal (P less than 0.001), whereas tyrosine levels were within or above normal; no significant differences between pre- and postoperative tryptophan or tyrosine levels; postoperative STD-TPN did not change predicted brain tryptophan concentration from preinfusion values, but BCAA-TPN decreased it (P less than 0.001), underscoring the common transport carrier; and preinfusion predicted brain tyrosine levels were decreased (P less than 0.001) by both types of TPN solutions. These results imply low substrate levels for brain serotonin and catecholamine synthesis, possibly affecting functions dependent on their control.

Amino Acids↗
PubMed1985

Aspects of amino acid and protein metabolism in cancer-bearing states.

Overt malnutrition is seen in about 40% of patients hospitalized for treatment of cancer. In patients whose primary treatment modality is surgical, morbidity and mortality is twice as high in the malnourished group as in the normally nourished patients. This clinically important malnutrition is a consequence of obligatory parasitism by the tumor, which grows at its own genetically determined rate and which competes effectively with the host for the limited available nutrients. Administration of extra nutritional support as total parenteral nutrition (TPN) can alter the tumor-host nutritional balance so that host repletion may occur. Provision of a significant proportion of TPN calories as fat diminishes the incidence of glucose intolerance and reduces the incidence of abnormal liver function. In vitro and in vivo studies both show that leucine is the significant controlling branched-chain amino acid in the TPN mixture, and adequate leucine content is a crucial component of effective TPN. Variations in TPN content of large neutral amino acids have important effects on brain tyrosine and tryptophan availability and hence may also effect neurotransmitter activity. Although the usefulness of TPN for correcting malnutrition in cancer patients is clear, the optimal choices of constituents for the TPN mixture continue to evolve.

Adenosine Triphosphate↗
PubMed1984

Effect of elemental diet on albumin and urea synthesis: comparison with partially hydrolyzed protein diet.

Enhanced nitrogen utilization occurs when adults with gastrointestinal disease are fed partially hydrolyzed proteins instead of isonitrogenous, isocaloric crystalline amino acids. A controlled trial was conducted to determine if this difference was also seen in malnourished stressed cancer patients and to gain an understanding of the underlying mechanism. Sixteen malnourished patients with head and neck cancer were prospectively randomized to either crystalline amino acid-glucose (CAA-G) or partially hydrolyzed protein-glucose (PHP-G) diets. Patients were fed via an enteral tube for 10 days starting on the second postoperative day. Blood SMA-6 and amino acid levels were measured on Days 1 and 10. Daily calorie counts and fluid balance were obtained. Daily 24-hr urine and stools were analyzed for total N during the last 5 days of the study period. The daily positive N balance with both diets was the same (CAA-G = +7.8 +/- 0.8 vs PHP-G = +8.2 +/- 1.0 g; mean +/- SE) and 3-methylhistidine:creatinine ratio did not differ. Patients on PHP-G diet gained significantly more weight (+0.5 vs - 1.5 kg; P less than 0.01) and had significantly higher serum albumin (3.2 +/- 0.2 vs 2.8 +/- 0.1 g/dl; P = 0.5) by the end of the 10th study day. Weight changes were not due to fluid retention: serum Na+, K+, creatinine and mean fluid intake for the two groups remained the same during the study period. A significantly greater rise in BUN occurred on the CAA-G diet (from 9.2 +/- 1.7 to 15.4 +/- 1.4 mg/dl; P less than 0.05) while BUN remained unchanged on the PHP-G diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Urea Nitrogen↗
PubMedDate not supplied

Plasma carotenoid profiles in normals and patients with cancer.

Most human cancers arise in epithelial tissues, which are critically dependent on vitamin A for normal differentiation and proliferation. Dietary carotenoids consist of individual retinoids--pro-vitamin A precursors and non-pro-vitamin A precursors-displaying different biological activity. Although epidemiological data suggest that low serum vitamin A levels were associated with an increased risk of cancer, it is not known whether one specific or all vitamin A carotenoids are involved. To assess whether the plasma carotenoids are related to the nutritional or cancer-bearing state, a study was conducted to measure total and individual carotenoids in four groups: cancer-bearing, malnourished; cancer-bearing, well-nourished; non-cancer, malnourished; and well-nourished volunteers of comparable age and sex. There was no difference in total carotenoids and pro-vitamin A precursors between the well-nourished--both normal volunteers and cancer patients. Malnourished cancer and non-cancer patients had significantly (p less than 0.05) lower value of both. Most of the circulating carotenoids in all groups were the non-pro-vitamin A precursors. Both malnourished cancer and non-cancer patients had lower values than well-nourished (p less than 0.05). Differences were related to nutritional state, rather than presence of cancer.

Adult↗
PubMedDate not supplied

Taurine-supplemented total parenteral nutrition and taurine status of malnourished cancer patients.

The status of plasma taurine and whether its concentration can be influenced by total parenteral nutrition (TPN) was determined in 51 malnourished fasting cancer patients after surgery and 7-14 days after starting TPN providing 41 +/- 2 kcal, 0.30 +/- 0.02 g N kg-1.day-1 and 40 mg pyridoxine. Plasma taurine was 50% lower in patients than in control subjects. Plasma taurine was significantly greater than baseline only after 14 days of TPN. We also studied the effects of surgery and taurine supplementation (8.6 mg.kg-1.day-1) on plasma and urine taurine concentrations in 12 malnourished patients. Preoperatively, all patients had normal plasma taurine concentrations; postoperatively, it was in the deficient range in 4 patients. Taurine-supplemented patients initially had higher than baseline concentrations; by day 10, none had subnormal levels. Subnormal taurine concentrations commonly occur in malnourished postoperative cancer patients; surgery further precipitates their fall. Plasma concentrations were maintained only with taurine-supplemented TPN.

Adult↗