Biomedical subjects

I Ramirez

Publications and source records attributed to I Ramirez.

At least 19 recordsLinked to original sources

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↗

PubMed1991

High-fat diets stimulate transient hyperphagia whereas wet diets stimulate prolonged hyperphagia in Fischer rats.

The effectiveness of several different kinds of diets in stimulating hyperphagia in Fischer strain rats was compared. Of three different high-fat diets examined, only one stimulated significant hyperphagia and stimulated weight gain; this diet was high in both fat and carbohydrate. However, this hyperphagia and increased weight gain was transient, lasting less than four weeks. A high-sucrose diet stimulated energy intake for only one week. In contrast, adding water to a high-starch diet or adding saccharin to a wet diet stimulated energy intake and weight gain for at least ten weeks. Once water or saccharin were removed from these diets, hyperphagia subsided or even turned into hypophagia, until body weights approached control levels. The degree of hyperphagia during the first week did not correlate with subsequent hyperphagia or weight gain. These results suggest that wet diets act by different mechanisms than do dry high-fat and high-sucrose diets.

Animals↗

PubMed1991

Starch flavor: apparent discrimination between amylopectin and amylose by rats.

Rats given a choice between dilute suspensions of corn amylopectin and corn amylose generally preferred amylopectin. The preference threshold for amylopectin was lower than the preference threshold for amylose (0.1% and 0.5%, respectively). Two sources of evidence indicate that the difference in preference for these two types of starch is due to an off-taste component in corn amylose rather than to an ability to discriminate between amylopectin and amylose per se: 1) rats given a choice of purified amylopectin and amylose from potato did not show a significant preference, and 2) aqueous extracts of amylose reduce preference for water and amylopectin, respectively. Extensive washing of corn amylose with ammonia-methanol, water and methanol did not completely remove the off-taste of corn amylose. Despite the difference in off-taste, rats trained to avoid amylopectin also avoided amylose. It is proposed that starch has two flavor components: a component due to starch itself that induces preference, and a component due to impurities that reduces preference.

Amylopectin↗

PubMed1991

High-dose cyclophosphamide-high-dose methotrexate with coordinated intrathecal therapy for advanced nonlymphoblastic lymphoma of childhood: results of a Pediatric Oncology Group study.

The Pediatric Oncology Group (POG) investigated a high-dose cyclophosphamide (CPM) high-dose methotrexate (MTX) regimen to determine therapeutic efficacy in confirmed advanced nonlymphoblastic non-Hodgkin's lymphoma (NHL) (stages III and IV) and B-cell acute lymphatic leukemia (B-ALL) in children. Another goal was to determine the comparative effectiveness of shortened maintenance treatment (2 versus 6 courses) in the study population. Systemic induction therapy included vincristine, prednisone, cyclophosphamide, and intermediate-dose MTX with leucovorin rescue. Superimposed intrathecal (IT) therapy included cytosine arabinoside for 2 successive days followed on day 3 by MTX. Intrathecal MTX was given 3 times during induction. At the end of induction, 2 days of triple (hydrocortisone, MTX, and cytosine arabinoside) therapy were given intrathecally (TIT). All patients then received a consolidation course of 4 doses of TIT, 2 doses of cyclophosphamide, and 4 more courses of vincristine and MTX with leucovorin rescue. Patients were then randomized to receive either 2 or 6 cycles of vincristine plus MTX with leucovorin rescue. The TIT was given with each cycle. Complete response rates by histology and Murphy stage (1) were as follows: undifferentiated lymphoma (DUL) stage III, 84/105 (80%): stage IV, 5/12 (42%); and other NHL [primarily large cell lymphoma (LCL)] stage III, 21/28 (75%); stage IV, 2/3 (67%). Event-free survival (EFS) at greater than 2 years was similar for patients with DUL and LCL, i.e., 65 and 61%, respectively. No significant difference in outcome was noted between patient groups receiving 2 or 6 maintenance treatments (p = .76). Treatment was notable for its modest toxicity following the early change to single-dose CPM therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1991

Chemoreception for an insoluble nonvolatile substance: starch taste?

Substances that are insoluble in both water and lipids, such as starch, are commonly assumed to be tasteless. Starch was suspended in water with a viscous gum. Rats given a choice of fluid containing starch and the same fluid without starch consistently preferred fluids containing starch. Rats were able to detect as little as 0.5% starch from several species of plants (corn, rice, wheat, and potato). In contrast, rats ignored comparable concentrations of cellulose suspended in water. Rats were also capable of choosing the fluid containing higher levels of starch when given a choice of 1 vs. 2% starch or 0.5 vs. 1% starch. This ability to detect starch did not appear to be mediated by salivary alpha-amylase because 1) raw starch is highly resistant to hydrolysis by salivary amylase, 2) starch preference was not correlated with the susceptibility of the starch to hydrolysis by salivary amylase, and 3) starch preference was not blocked by partial or extensive desalivation. Attempts to extract impurities with either organic solvents or water did not provide any evidence that such impurities contribute to starch preference. These experiments point to a seemingly novel form of chemoreception that could be useful to animals that need to identify starch-rich foods.

Amylases↗

PubMed1990

Establishment and characterization of human B-cell lymphoma cell lines using B-cell growth factor.

B-cell non-Hodgkin's lymphomas (NHL-B) have been difficult to establish in long-term cell culture using standard techniques. We report the establishment of five representative cell lines from high grade NHL-B using B-cell growth factor (BCGF). The five NHL-B cell lines display the morphologic, immunophenotypic, genotypic, and biologic characteristics of the lymphoma cells present in the original diagnostic specimen. The cell lines showed at least a sevenfold dose-dependent increase in proliferation in vitro over background in the presence of BCGF. Other putative B-cell growth-stimulating cytokines showed no significant proliferative activity or were inhibitory in some cases. NHL-B cell lines secreted growth factor(s) into culture supernatants that mediated at least a fivefold dose-dependent increase in cell proliferation in autochthonous lymphoma cells and a 10-fold or greater stimulation in growth factor-dependent normal B cell lines in vitro. The cell lines show monoclonal rearrangements of IgH genes and nonrandom chromosomal abnormalities characteristic of NHL-B, while the expression of Epstein-Barr virus associated antigen (EBNA-I) is present in two of the five cell lines. The studies show that lineage-specific growth factors may be used to establish neoplastic B cell lines in vitro, which are important experimental systems for cellular and molecular studies in the NHL-B.

Adolescent↗

PubMed1990

Dietary hyperphagia in rats: role of fat, carbohydrate, and energy content.

Dietary energy, fat and carbohydrate content were varied to determine the nutritional factors responsible for hyperphagia induced by feeding rats high-fat diets. In the first experiment, rats were fed isoenergetic high-fat or high-carbohydrate diets for 2 weeks. Weight gain and energy intake were lower in rats given the high-fat diet. When some of the rats were switched to a diet that was high in fat, carbohydrate and energy, gram food intake was initially unchanged, resulting in a substantial increase in energy intake and weight gain. Energy intake gradually declined over the 4 weeks following the switch to the high-energy diet. In the second experiment, rats were fed high-fat diets that were either high or low in carbohydrate content and either high or low in energy content (kcal/g). Rats fed a high-fat diet that was high in energy and carbohydrate ate the most energy and gained the most body weight and carcass fat. In the third experiment, rats were fed high-carbohydrate diets varying in fat and cellulose content. Energy intake and body weight gain varied directly as a function of caloric density regardless of the fat or cellulose content of the diets. It is concluded that hyperphagia induced by feeding high-fat diets is not due to the high dietary fat content alone. Rather, high levels of fat, carbohydrate, and energy interact to produce overeating and obesity in rats fed high-fat diets.

Animals↗

PubMed1990

What do we mean when we say "palatable food"?

The word palatability and related words have not been used in a consistent way. Palatability may be a property of a food, of the organism eating the food, or both. Investigators have failed to distinguish different possible meanings of the statement: "palatable foods increase intake". This may indicate: (1) a simple observation that some foods stimulate more intake than others, (2) an innate response to the taste of foods that alters appetite, (3) a correlate of food intake that does not itself affect intake, and (4) a link in a causal chain involving prior associations between foods and their postingestive consequences.

Appetite↗