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Biomedical subjects

R O Brown

Publications and source records attributed to R O Brown.

At least 55 records · Page 3Linked to original sources
PubMed1990

Use of selected visceral protein measurements in the comparison of branched-chain amino acids with standard amino acids in parenteral nutrition support of injured patients.

Twenty injured patients in the intensive care unit were randomized to receive parenteral nutrition with either 21% (STD) or 46% (HBC) branched-chain amino acids to compare the response of nitrogen balance (NB), somatomedin-C/insulin-like growth factor I (SMC), circulating fibronectin (FBN), and prealbumin (PA). NB was measured and serum collected for SMC, FBN, and PA on days 1, 4, 7, 14, and 21 of nutritional intervention. The treatment groups did not differ significantly for age, weight, injury severity score, trauma score, Apache II score, acute-phase protein concentrations, or type of injury. Comparison of baseline measurements revealed no significant differences in SMC, FBN, or PA. Both groups received similar doses of nonprotein energy and nitrogen. Baseline urea nitrogen excretion was slightly higher in the STD group (216 +/- 55 vs 268 +/- 54 mg/kg/day p = 0.049). Although NB was significantly improved over baseline during subsequent study days, there were no differences between groups after the day-1 measurement. SMC increased significantly from baseline on day 4 in the STD group, on day 7 in the HBC group, and on days 14 and 21 in both groups. There was no significant difference in SMC concentrations between groups on any day. Each group demonstrated a significant increase in PA from baseline on days 7, 14, and 21; however, no difference was seen when groups were compared. FBN increased significantly from baseline on day 14 in the HBC group and on days 7 and 14 in the STD group. FBN measurements were significantly different between groups on day 14 (STD, 179 +/- 71 vs HBC, 229 +/- 59 micrograms/ml; p less than 0.05). NB, PA, SMC, and FBN improve significantly during parenteral nutrition of traumatized patients. With the measured variables, there appears to be no significant difference between STD or HBC amino acids when used as part of parenteral nutrition in injured patients.

Amino Acids↗
PubMed1989

Use of fibronectin and somatomedin-C as nutritional markers in the enteral nutrition support of traumatized patients.

Enteral nutrition support was provided to 12 critically ill, traumatized patients by continuous NG infusion with a nutritionally complete formula for at least 7 consecutive days. Serum for fibronectin (Fn) and somatomedin-C (Sm-C) was collected and nitrogen balance (NB) was measured on days 1, 4, 7, 14, 21, and 28 of the study period. Estimated energy and protein requirements were based, respectively, on the patient's calculated basal energy expenditure multiplied by a stress factor and urea nitrogen excretion (plus 4) during 24-h urine collections. Enteral feedings were started 5.3 +/- 3.8 days after injury; patients received an average of 33.2 +/- 3.9 kcal/kg.day and 1.5 +/- 0.4 g protein/kg.day. Fn concentrations increased significantly (p less than .05) from baseline on study days 7, 14, 21, and 28, whereas NB increased significantly (p less than .05) on study days 4, 7, 14, 21, and 28. Significant correlations were found between Fn and NB (r = .52, p less than .005), Fn and cumulative caloric intake (r = .54, p less than .005), and Fn and cumulative nitrogen intake (r = .62, p less than .005). There were no significant changes observed with Sm-C concentrations during the study period. Measurement of Fn concentrations appears to have potential as a nutrition support marker in traumatized patients, particularly in monitoring short courses of nutrition support. The role of Sm-C as a nutrition marker requires further investigation.

Adolescent↗
PubMed1989

Neuroendocrine bag cells of Aplysia are activated by bag cell peptide-containing neurons in the pleural ganglion.

1. The generation of egg-laying behavior in the marine mollusk Aplysia involves a prolonged burst discharge in the neuroendocrine bag cells, which secrete neuropeptides derived from the egg-laying hormone/bag cell peptide (ELH/BCP) precursor protein. 2. Besides the bag cells, which are located in the abdominal ganglion, small clusters of neurons in the cerebral and pleural ganglia also express the ELH/BCP neuropeptides. We made intracellular recordings from 32 of these ELH/BCP cells in right pleural ganglia, in 18 preparations, to characterize their physiological properties and their functional relationship to the bag cells. 3. The identification of these ELH/BCP cells was confirmed by pressure injection of Lucifer yellow and subsequent immunocytochemical processing for alpha-BCP immunoreactivity. 4. The basic electrophysiological properties of the pleural ELH/BCP cells were similar to those of the bag cells. These pleural cells were directly demonstrated to be electrically coupled, and direct intracellular stimulation of individual pleural ELH/BCP cells initiated prolonged, synchronous burst discharges in the entire cluster through a positive feedback mechanism. 5. Burst discharges elicited in the pleural ELH/BCP cells consistently initiated burst discharges in the bag cells. Bag cell burst discharges were less effective in initiating burst discharges in the pleural ELH/BCP cells, indicating that there were reciprocal but asymmetrical connections. 6. The results show that the pleural ELH/BCP cells are functionally coupled to the bag cells. They support the hypothesis that the pleural ELH/BCP cells are part of the descending pathway that initiates bag cell activity and egg-laying behavior, in vivo.

Action Potentials↗
PubMed1989

Parenteral nutrition in the critically ill patient.

The metabolic alterations, nutritional and metabolic assessment, and nutritional requirements of critically ill patients are discussed, and parenteral nutrition support therapies are reviewed. Physiological alterations in the metabolism of the injured or septic patient are mediated through the interactions of neuroendocrine, cardiovascular, toxic, and starvation responses. These responses cause mobilization of nutritional substrates in an effort to maintain vital organ function and immune defenses. A patient's nutritional status can be determined from anthropometric measurements, creatinine excretion rate, and evaluations of protein stores and immune reserves and function; body weight is a poor indicator. Nitrogen-balance calculations are also useful for determining the adequacy of nutritional intake and the degree of metabolic stress. Early assessments of nutritional status may assist in identifying those patients for whom nutritional support interventions are needed. Nutritional requirements are altered by the metabolic responses to injury and sepsis. Studies suggest that use of nutrient solutions enriched for branched-chain amino acids may enhance nitrogen retention and that energy expenditures in injured or septic patients are only moderately elevated. Most nonprotein calories in parenteral nutrient solutions are provided as glucose, but lipids are an important source of energy in the critically ill patient who has high energy requirements or carbohydrate intolerance; however, clearance of lipids may be decreased. Fluid, electrolyte, and mineral status must be evaluated frequently. Critically ill patients have unique nutritional requirements, and parenteral nutrition support therapies for these patients are being investigated and refined.

Critical Care↗
PubMed1989

Positive feedback by autoexcitatory neuropeptides in neuroendocrine bag cells of Aplysia.

Neurohormones are often secreted in large amounts from neuroendocrine cells during episodes of synchronous, repetitive spike activity. We report evidence that this pattern of activity in the neuroendocrine bag cells of Aplysia involves positive feedback by autoexcitatory transmitters. Intracellular stimulation of individual bag cells caused slow depolarizing afterpotentials and synchronous afterdischarges in the entire population of bag cells. Application of the bathing medium collected during bag cell activity mimicked these responses. Application of alpha-, beta-, or gamma-bag cell peptides (BCPs), 3 structurally related neuropeptides released from bag cells, also mimicked these responses. These autoexcitatory BCPs fulfill most of the strict criteria necessary for classification as neurotransmitters in this system. This is the first biological activity reported for beta- and gamma-BCPs and brings to 4 the number of bag cell neuropeptides derived from the egg-laying hormone/BCP precursor that are putative cotransmitters. Positive feedback by autoexcitatory transmission may provide a general mechanism for the generation of episodic activity in neuroendocrine systems.

Animals↗
PubMed1988

Effect of albumin supplementation during parenteral nutrition on hospital morbidity.

Because several studies have shown a significant inverse correlation between depressed serum concentrations of albumin and hospital morbidity, a study with central total parenteral nutrition (TPN) with normal serum albumin (NSA) in hypoalbuminemic patients was conducted. Sixty-one patients who required central TPN were randomized into one of two groups: group 1 (n = 31) received TPN plus NSA (25 to 37.5 g/day) until their measured serum albumin was greater than 3 g/dl, and group 2 (n = 30), who received TPN alone. All patients were followed for hospital complications until discharge or death. The groups were well matched for age, sex, major diagnoses, initial serum albumin concentrations, hospital complications before TPN, and number of operative procedures. Both groups received comparable doses of energy (37.2 +/- 89 vs. 3.30 +/- 6.2 kcal/kg.day) and protein (1.6 +/- 0.4 vs. 1.6 +/- 0.3 g/kg.day). After initiation of TPN, there were significantly more hospital complications in group 2 (1 = 1.1 +/- 1.4, n = 33; 2 = 2.6 +/- 3.0, n = 80, p less than .01). When complications in the patient groups were stratified, significantly more patients in group 2 developed pneumonia (18 vs. 9, p less than .05) and septicemia (11 vs. 2, p less than .05). Increasing serum albumin concentrations with NSA in hypoalbuminemic patients receiving central TPN appears to be associated with a reduction in hospital morbidity.

Adult↗
PubMed1987

Central actions of R15, a putative peptidergic neuron in Aplysia.

We report that the bursting pacemaker neuron R15 has central actions on other identified neurons in the abdominal ganglion of Aplysia california. The follower cells are located on the dorsal surface of the left lower quadrant of the ganglion and include members of the LC cell cluster. A spontaneous burst of impulses in R15 produces a slow, graded, excitatory potential of up to 8 mV in follower cells. The response begins about 2-3 s after the first impulse in an R15 burst, and reaches its peak at about 4-6 s (corresponding approximately to the end of the R15 burst). In some preparations a biphasic response was seen composed of the early depolarization followed by a slower excitatory or inhibitory phase. All the responses were blocked when R15 was hyperpolarized to prevent spiking. The magnitude of the response was reduced in a graded fashion by prematurely terminating the R15 burst with hyperpolarizing current and was increased when depolarizing current was injected into R15 during a burst. Central actions of R15 were observed in only 28% of our preparations, and their presence may depend on unknown physiological factors. The effects are likely to be mediated by R15 neuropeptides. The accessibility of both R15 and its targets in this preparation should facilitate further analysis of this interaction.

Abdomen↗
PubMed1986

Isolation and primary structure of the califins, three biologically active egg-laying hormone-like peptides from the atrial gland of Aplysia californica.

The atrial gland of the marine mollusk Aplysia californica contains several biologically active peptides that are thought to be important in reproductive function. In the present study, three novel peptides, which we named califin A, B, and C, were purified from extracts of atrial glands by high performance liquid chromatography, and their primary structures were determined. Each consists of a 36-residue subunit bound by a single disulfide bond to an 18-residue subunit. The large subunits differ from each other by one or two residues, whereas the small subunits are identical. The large subunits are 78-83% homologous to egg-laying hormone (ELH), a 36-residue peptide synthesized by the neuroendocrine bag cells of Aplysia. Like ELH, the califins excite LB and LC cells of the abdominal ganglion and cause egg laying when injected into sexually mature animals. Based on previously described DNA sequence data, each califin is likely to be derived from one of several precursor proteins that are encoded by members of the ELH gene family. Califin A is encoded on the peptide A precursor, and califin B may be encoded on the peptide B precursor. No gene encoding califin C has been sequenced. Because peptides A and B are also biologically active, the precursors encoding them and califins A and B are polyproteins. The possible role of atrial gland peptides as pheromones is discussed.

Amino Acid Sequence↗
PubMed1986

Chromium deficiency after long-term total parenteral nutrition.

A 63-year-old female developed unexplained hyperglycemia and glycosuria during administration of a total parenteral nutrition regimen on which she had been stable for several months. Because the patient had no history of diabetes or evidence of an infection, chromium deficiency was considered. Plasma chromium level was 0.1 microgram/dl (laboratory reference interval: 1.8-3.8 micrograms/dl). Fourteen days of supplemental intravenous chromium chloride (200 micrograms/day) allowed complete withdrawal of exogenous insulin with no further hyperglycemia or glycosuria. Correction of unexplained glucose intolerance following vigorous chromium supplementation indicates that the patient had chromium deficiency. Subsequent plasma chromium levels remained unchanged, possibly reflecting the sensitivity limits of the assay that was used, the uncertainty that exists regarding appropriate reference intervals for this element, and the fact that plasma levels do not always correlate with total body stores. The patient did not manifest peripheral neuropathy, which was present in one of the two previously reported cases, nor encephalopathy, which was reported in the other. We conclude that this patient developed chromium deficiency as a result of inadequate administration of chromium in the parenteral formula (6 micrograms/day) plus excessive enteric losses, and she presented with glucose intolerance as the only clinical manifestation of the deficiency. Caution should be exercised when interpreting plasma chromium in patients with suspected deficiency.

Blood Glucose↗
PubMed1986

Plasma protein fraction and albumin use: the effect of medical staff education.

A 6-week audit evaluating the use of plasma protein fraction and albumin was conducted and study data demonstrated that these colloids were being inappropriately prescribed. The P & T Committee decided to use educational rather than restrictive methods to improve colloid prescribing. Follow-up audits were performed, one immediately following staff education and another 1 year after the first audit. Although the educational actions employed in this drug utilization review appeared to have an immediate impact, the effect was not sustained long-term, indicating the need for periodic medical staff education. Methods of effective educational intervention as reported in the literature are discussed.

Colloids↗