Biomedical subjects

I Ramirez

Publications and source records attributed to I Ramirez.

At least 37 records · Page 2Linked to original sources

PubMed1994

Chemosensory similarities among oils: does viscosity play a role?

It is widely thought that viscosity plays an important role in the perception of fats. Rats were conditioned to avoid oil suspensions by treating them with lithium chloride after they had ingested the oil suspension. Control rats received the same lithium chloride injection after they drank vehicle. Three, chemically different, oils were examined, triglyceride oil, silicone oil and mineral oil. Rats trained to avoid a 4% aqueous suspension of one of these oils, reliably avoided suspensions containing any of the other oils, although the rats could discriminate between the oils. The viscosity of the oil suspension was slightly greater than the viscosity of the vehicle alone. However, rats trained to avoid an oil suspension, did not avoid a fluid having a viscosity similar to that of the oil suspension. In order to assess the possibility that rats could sense the viscosity of the oil separately from that of the vehicle, rats were tested for their aversion to oils having viscosities much higher and much lower than that of the oil they were trained to avoid. Rats trained to avoid triolein having a viscosity of 67 cp, reliably avoided silicone oils having viscosities of 5 and 203 cp. However, rats trained to avoid oil did not avoid an oil-free fluid having a viscosity of 22-29 cp. A final experiment examined whether the use of viscous or non-viscous vehicles influenced the conditioned aversion. No significant effect of vehicle viscosity appeared. Thus, chemically-diverse oils are perceived, by rats, to have some perceptible attribute in common. It is proposed that this common physical attribute is boundary lubrication rather than viscosity.

Animals↗

PubMed1994

Stimulation of fluid intake by carbohydrates: interaction between taste and calories.

Rats were trained in an apparatus that infused water or nutritive fluids into their stomachs every time that they drank flavored fluids. Rats given saccharin to drink by mouth drank more fluid than rats given cherry-flavored water to drink. Furthermore, rats given saccharin to drink ingested much more fluid if they were given intragastric infusions of 6% carbohydrate than intragastric infusions of plain water. This stimulatory effect of carbohydrate infusion occurred within 1 or 2 days of training and was very large, amounting to > or = 70% increase in fluid intake compared with rats drinking saccharin and infused with water. On the other hand, infusions of 6% carbohydrate had no effect on the intake of rats given cherry-flavored water to drink. In an attempt to determine whether rats could be trained to respond to cherry flavor at all, rats were infused with a liquid diet whenever they drank cherry or saccharin-flavored water. When dry food was withheld, the rats learned to increase fluid intake so as to feed themselves. The rats given saccharin to drink acquired this task more readily than rats given cherry flavor to drink, but both groups took in normal amounts of food by the end of the 10-day training period. It is concluded that it is much easier to condition an increase in fluid intake with intragastric infusions of carbohydrate than with an arbitrary nonsweet flavor.

Animals↗

PubMed1994

High-dose mercaptopurine followed by intermediate-dose cytarabine in relapsed acute leukemia.

PURPOSE: This phase I/II study was designed to explore the feasibility, toxicity, and potential efficacy of administering high-dose continuous intravenous mercaptopurine (6MP) followed by intermediate-dose continuous intravenous cytarabine (Ara-C) to children with relapsed or unresponsive acute leukemia. PATIENTS AND METHODS: Twenty-three children with relapsed or unresponsive acute leukemia (13 myeloid, 10 lymphoid) were entered onto the study. After initial hydration and alkalinization, 1,000 or 1,250 mg/m2 of 6MP was administered by continuous intravenous infusion over 24 hours. Following another period of hydration, 500 mg/m2 of Ara-C was administered by continuous intravenous infusion daily for 4 days. In 17 children, plasma concentrations of 6MP were measured at hours 4, 24, and 27 of the 6MP infusions. Plasma concentrations of Ara-C were measured at hours 8, 24, 48, 72, and 96 of the Ara-C infusions. Intracellular Ara-C triphosphate (Ara-CTP) concentrations were measured in peripheral-blood leukemia cells of the five patients with sufficient cells for measurement. Children who developed remission received repeated courses of this regimen every 3 to 4 weeks until relapse or completion of 12 courses. RESULTS: Of 13 children with acute myeloid leukemia (AML), six developed complete remissions (CRs) lasting 7 months to nearly 4 years. Two children remain in CR with normal growth, development, and health 3 years after cessation of treatment. Of 10 children with acute lymphoid leukemia (ALL), one had a CR of 2 months' duration. Dose-limiting toxicity consisted of severe hematosuppression with fever, neutropenia, and serious infection. There were two toxic deaths. The mean steady-state plasma concentrations of 6MP were approximately 4 mumol/L and of Ara-C approximately 3 mumol/L. The median Ara-CTP concentration in peripheral-blood leukemia cells was 308 mumol/L at hour 8 of the Ara-C infusion. CONCLUSION: High-dose continuous intravenous 6MP followed by intermediate-dose intravenous Ara-C produced CRs of longer than 6 months in approximately half of children with relapsed or unresponsive AML. Further study of this drug regimen is justified.

Acute Disease↗

PubMed1993

Food deprivation reduces rats' oil preference.

Rats normally prefer dilute oil suspensions over vehicle, but this preference can be abolished by exposing them to dilute oil suspensions during a period of food deprivation. In the first series of experiments, rats were given a choice of 0.5-0.9% triolein vs. vehicle for 4 consecutive days each week for 3 weeks. Food was available ad libitum on days 1, 2 and 4; no food was available on day 3. Preference for oil suspension dropped sharply after, but not during, each occasion that food was withheld. Similar experiments using starch, Polycose, or sucrose did not show comparable deprivation-induced changes in preference. The second series of experiments included separate control and experimental groups. The experimental group was food deprived for 1 day when test fluids were available. The control group was food deprived the day after the test fluids were available. Food was returned and the test fluids were removed for a few days. Fluid preference was then retested with food available ad libitum. After this cycle of two preference tests was repeated 1-2 times, the experimental group showed substantially lower oil preference than did the control group. Similar results were obtained with 0.5% triolein, 0.5% soybean oil, and 5% soybean oil. A similar experiment in which a vanillin-citral flavor was used instead of oil did not show such an effect. However, preference for the vanillin-citral flavor was decreased in rats exposed to a mixture of this flavor and oil while they were food deprived. It is proposed that rats readily learn to associate oil flavor, but not other flavors, with the aversive effects of food deprivation.

Acyclic Monoterpenes↗

PubMed1993

Rats discriminate between starch and other substances having a similar texture.

Studies examined the contribution of textural factors to the ability of rats to sense starch. If rats sense the abrasive effects of starch suspensions, conditioned aversions to starch should generalize to substances having a similar texture. Two substances having a texture similar to that of starch were examined, polymeric dialdehyde (a product derived from starch) and inulin (a polymer of fructose). Rats were trained to avoid dilute suspensions of rice starch, potato starch, polymeric dialdehyde, or dahlia inulin, by injecting them with lithium chloride after they drank the test substance. Generalization tests revealed that rats trained to avoid rice or potato starch subsequently avoided corn starch, whereas rats trained to avoid polymeric dialdehyde or dahlia inulin did not avoid corn starch. Rats trained to avoid polymeric dialdehyde avoided this substance to a greater degree than did rats trained to avoid rice or potato starch. Rats trained to avoid dahlia inulin avoided this substance to a greater degree than did the rats in the other groups, but avoidance of dahlia inulin did not generalize to chicory inulin. Untrained rats showed little or no preference for dilute suspensions of polymeric dialdehyde or inulin, but did prefer starch over vehicle. It is concluded that tactile sensitivity does not play a large role in the perception of dilute starch suspensions.

Animals↗

PubMed1993

Relative preference for starch and sugar in rats.

When given a choice between fluids containing equal amounts of corn starch or glucose, Fischer rats preferred the fluid containing starch when the fluids contained 0.5%, 1%, 5%, or 20% carbohydrate, but not when the fluids contained 10% carbohydrate. Fischer rats preferred 0.5% sucrose over 0.5% starch on the first day of testing, but then switched to preferring starch. Rats of the CD strain also preferred 0.5% starch over 0.5% sucrose or 0.5% glucose, but showed no reliable preference when offered a choice of 5% starch vs. 5% sucrose or 5% glucose. Most experiments used corn starch, but rats prefer 1% rice, wheat, and tapioca starch over 1% glucose. Rats given only one substance to drink, drank more fluid if the fluid contained 1% starch than if it contained 1% glucose. Preexposing rats to either glucose or starch for 3 days did not influence subsequent preference for starch over glucose. Since the starch and glucose mixtures used in the present work had the same number of calories, preference for starch over glucose must be attributed to the hedonic effects of starch flavor rather than to the postingestive effects of starch.

Animals↗

PubMed1993

Role of olfaction in starch and oil preference.

Two different techniques were used to assess the role of olfaction in the preference rats show for dilute nutrient suspensions and solutions. Removal of the olfactory bulbs reduced but did not abolish preference for 1% starch and oil emulsions. Removal of the olfactory bulbs also reduced preference for sucrose, Polycose, and saccharin. In another experiment, rats were rendered anosmic with intranasal zinc sulfate. The degree of anosmia was evaluated by measuring preference for an aqueous solution of citral and vanillin. Rats whose avoidance of citral plus vanillin had been abolished by zinc sulfate continued to prefer a 1% starch suspension over vehicle, although starch preference was significantly reduced. It is concluded that starch and oil preference is mediated by both olfactory and nonolfactory cues.

Animals↗

PubMed1992

Neonatal extinction of liver lipoprotein lipase expression.

In contrast to the complete absence of lipoprotein lipase (LPL) mRNA in adult rat liver, fetal and neonatal rat liver contain substantial amounts of LPL mRNA, which is translated in active LPL protein as can be deduced from the presence of LPL activity in this organ. At this neonatal stage, both the relative abundance of LPL mRNA and LPL activity increased with starvation. During the suckling period, LPL mRNA and LPL activity gradually decreased until both parameters were undetectable. While the administration of L-thyroxine or hydrocortisone enhanced the disappearance of LPL mRNA, induced hypothyroidism delayed its disappearance. In adult animals induced hypothyroidism could not reactivate LPL mRNA production in the liver. The data presented suggest that liver LPL production responds to changes in the nutritional state and becomes extinguished during development, in a fashion reminiscent to the extinction of alpha-fetoprotein. This extinction of LPL gene expression is influenced by hormonal factors.

Animals↗

PubMed1992

Severe osteopenia and vertebral compression fractures after complete remission in an adolescent with acute leukemia.

Acute leukemia frequently presents with skeletal symptoms; however, the etiologies of bone pain and osteopenia are poorly understood. We present the case of an adolescent girl with acute leukemia who developed vertebral fractures after being in complete remission for 3 months. Bone mineral density was very low (less than 0.6 g/cm2) but remained stable during the subsequent 3 months despite continuation therapy with methotrexate and prednisone. Findings of a bone biopsy were consistent with a recent episode of aggressive bone resorption. We suggest that paracrine secretion of lymphokines may mediate loss of bone mass during the active phase of acute leukemia, although clinical bone disease may not develop until after complete remission is achieved.

Acute Disease↗

PubMed1992

Is starch flavor unitary? Evidence from studies of cooked starch.

Although starch is the world's most abundant nutritive carbohydrate, its sensory properties are not as well understood as those of sugars. Previous researchers have assumed that all starches have the same flavor. The present experiments examined flavor differences among starches. Untrained rats were offered a choice of suspensions containing raw versus cooked starch. For some starches (potato and rice), rats strongly preferred cooked over uncooked starch. For other starches (regular corn, corn amylopectin, and wheat), rats showed little or no preference for cooked over uncooked starch. In order to determine whether the greater preference for cooked starch reflects a difference in flavor intensity, rats were conditioned to avoid potato or corn amylopectin starches by pairing ingestion of these substances with lithium chloride injections. Rats trained to avoid raw starch also avoided cooked starch, indicating that cooked and raw starch have similar flavors. However, when these trained rats were offered a choice between cooked and raw starch, they avoided the raw starch; this result is inconsistent with the assumption that cooking enhances the intensity of starch flavor. Similar results were obtained with corn amylopectin and potato starch, even though these starches differ greatly with regard to the effects of cooking on preference in untrained rats. However, rats trained to avoid potato starch avoided this starch to a greater degree than did rats trained to avoid corn amylopectin; conversely, rats trained to avoid corn amylopectin avoided this starch to a greater degree than did rats trained to avoid potato starch. Therefore, the flavor of starch is complex; there are specific flavor notes related to species and cooking.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylopectin↗

PubMed1992

Malaise can condition avoidance of high-viscosity fluids.

Previous researchers have assumed that malaise-inducing drugs condition aversions to tastes more readily than to textural stimuli. The present report shows that rats given a single injection of lithium chloride after they have sampled a viscous fluid, subsequently showed greater avoidance of that fluid than did control rats. Rats learned this response even when the lithium chloride injection was given 60 min after they sampled the viscous fluid. The generalization gradient for viscous fluids is apparently very broad, because rats trained to avoid 11 or 95 cp fluids subsequently avoided 11 and 95 cp fluids to a similar degree. Nevertheless, this avoidance is based on textural cues because rats injected with lithium chloride after ingesting one viscous fluid subsequently avoided a wide variety of viscous fluids, including those made from carbohydrate polymers (algin, guar, xanthan), a modified carbohydrate (methyl cellulose), and a protein (methyl cellulose). However, the flavors of viscous gums may influence texture aversion.

Animals↗

PubMed1992

Chemoreception for fat: do rats sense triglycerides directly?

Rats given a choice between fluid containing 0.1-0.5% triglyceride oil and the same fluid without oil, generally preferred the fluid containing oil. Several experiments indicate that this preference is based on the detection of impurities rather than triglycerides per se. Rats preferred crude triolein to a greater degree than they did highly purified triolein or corn oil. Rats did not show any preference for or aversion to tristearin, a fat that does not decompose as readily as triolein. Rats that have been trained to avoid a dilute suspension of triolein, also avoided an aqueous extract of triolein. Since rats that had been trained to avoid triolein oil also avoided corn oil, it seems likely that different oils may possess similar impurities. Since training rats to avoid mineral oil did not reduce preference for triolein, these substances may have different flavors. It is proposed that rats use fat decomposition products to detect the presence of fats in foods.

Animals↗

PubMed1992

Does reducing the rate or efficiency of digestion reduce food intake?

Two strains of rats (Charles River CD and Lewis) were fed high-moisture (71% water) diets containing 50-300 mg acarbose/kg dry diet for 1-3 wk. Acarbose impaired carbohydrate digestion in both strains, as evidenced by increased fecal excretion and increased intestinal contents. For both strains the highest dose of acarbose tended to stimulate food intake, whereas an intermediate dose (100 mg/kg) inhibited food intake. The lowest dose (50 mg/kg) had no significant effect. In general the food intake-promoting effect of acarbose was more pronounced in CD rats, whereas the food intake-inhibiting effect of acarbose was more pronounced in Lewis rats. To determine whether increased intestinal bulk, due to undigested food, was responsible for the reduced food intake, another experiment was conducted in which Lewis rats were fed diets containing 5-25% cellulose. Although this level of cellulose should have increased fecal bulk to the same degree as acarbose, cellulose increased rather than decreased food intake. It is proposed that the presence of incompletely digested food in the digestive tract can inhibit food intake for several days. Because manipulating diet moisture altered energy intake without altering percentage of food excreted as feces, it is proposed that acarbose and diet moisture alter food intake by different mechanisms.

Acarbose↗

PubMed1991

Results of a changing treatment philosophy for children with stage I Hodgkin's disease: a 35-year experience.

Over the last four decades, significant changes have occurred in the management of childhood stage I Hodgkin's disease. Between 1949 and 1984, 50 children, ages 4 to 16 years, were treated for stage I Hodgkin's disease at The University of Texas M. D. Anderson Cancer Center. Nineteen children had clinically staged (CS) disease. Thirty-one patients were pathologically staged (PS). Thirty-four children were treated with radiotherapy only, 12 were treated with both radiotherapy and chemotherapy, and 3 patients were treated with combination chemotherapy alone. All patients were followed from 32 to 311 months (median 170 months). Five-, 10-, and 15-year actuarial survival rates for all patients were 94, 89, and 84%, respectively. The corresponding freedom from relapse (FFR) rates were 76, 69, and 69% respectively. The 10-year actuarial survival and FFR rates for CS patients were 79 and 42%. The corresponding rates for PS patients were 97 and 86%. In patients with PSI disease, actuarial 10-year FFR rates of 100% were obtained either with regional radiotherapy alone or with combination chemotherapy and involved field radiotherapy. The following delayed adverse effects of treatment were observed: growth abnormalities in 17, aspermia in 3, thyroid abnormalities in 11 (two carcinomas), and second malignancies beyond the radiotherapy fields in 2. We conclude with a recommendation of combined chemotherapy and involved field radiation for children who have not fulfilled their growth potential, to achieve high cure rates, while minimizing morbidity.

Adolescent↗

PubMed1991

Thresholds for starch and Polycose are lower than for sucrose in rats.

Detection thresholds for corn starch, Polycose and sucrose in water were assessed by a new technique. Rats were trained to avoid these carbohydrates by giving them fluid containing carbohydrate mixed with lithium chloride on some days, and fluid containing sodium chloride with no carbohydrate on other days. Rats trained by this procedure avoided the substance that they were trained to avoid, but did not avoid other substances. Thus rats trained to avoid starch avoided mixtures containing as little as 0.025% starch, but did not avoid Polycose, sucrose or sodium chloride. Rats trained to avoid Polycose avoided fluids containing as little as 0.01% Polycose, but did not avoid fluids containing starch or sucrose. Finally, rats trained to avoid sucrose avoided fluids containing as little as 0.05% sucrose, but did not avoid fluids containing starch or Polycose. Therefore, rats possess a keen sensitivity for starch, a substance that is commonly thought to be tasteless. Furthermore, starch, Polycose and sucrose are discriminable from each other.

Animals↗

PubMed1991

Influence of experience on response to bitter taste.

Sucrose octaacetate, which tastes bitter to humans, can reduce the energy intake of rats when added to their diet. The reduction in energy intake is transient, lasting no more than 5 weeks. Rats that no longer reduce intake in response to sucrose octaacetate still avoid food containing it in choice tests, although to a lesser degree than rats having no previous experience with sucrose octaacetate. The ability of sucrose octaacetate to reduce preference without reducing long-term intake accounts for the previous finding that a wet diet containing sucrose octaacetate can stimulate hyperphagia yet be less preferred than the control diet. Sucrose octaacetate was more effective in reducing intake of a wet than of a dry diet. This last observation indicates that adding water to a food makes it easier for an animal to taste its food.

Animals↗

PubMed1991

Does starch taste like Polycose?

Rats are capable of tasting or detecting maltooligosaccharides (e.g., Polycose) and starch in water, two substances that are bland to humans. Because both substances are glucose polymers, it has been suggested that they may be detected by the same mechanism. The present experiments examined whether rats conditioned to avoid one of these substances also avoid the other. Rats were injected with lithium chloride after being allowed to drink a 3% corn starch suspension. These rats subsequently avoided corn, potato, rice, and waxy maize (high-amylopectin) starch but did not avoid 0.1-3% Polycose Rats treated with lithium chloride after ingesting 3% Polycose avoided 3% and 0.5% Polycose, but they did not avoid 3% corn starch, 6% corn starch, or 3% waxy maize starch. These results indicate that rats can discriminate between starch and Polycose (maltooligosaccharides). It therefore seems likely that Polycose and starch have different sensory qualities.

Animals↗

PubMed1991

Strain differences in dietary hyperphagia: interactions with age and experience.

The development of susceptibility to dietary hyperphagia was examined in two strains of rats. Juvenile Lewis and CD rats fed a wet diet initially eat less energy than do rats fed the same diet in dry form. As the rats approach adulthood, rats fed the wet diet consume more energy than rats fed the dry diet. Lewis rats began displaying hyperphagia at an earlier age than did CD rats. However, Lewis rats, unlike CD rats, fed dry diet during the juvenile stage and subsequently switched to wet diets, displayed only transient hyperphagia. Variability between animals within a group was substantially smaller in Lewis than in CD rats, indicating that genetic factors may be responsible for the differences between the two strains. Thus, susceptibility to dietary hyperphagia is influenced by interactions between strain of rat, age of testing, and type of diet fed in the juvenile stage.

Aging↗