Altered taste in a 58-year-old patient.
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Phenylthiocarbamide tastes intensely bitter to some individuals, but others find it completely tasteless. Recently, it was suggested that phenylthiocarbamide elicits bitter taste by interacting with a human G protein-coupled receptor (hTAS2R38) encoded by the PTC gene. The phenylthiocarbamide nontaster trait was linked to three single nucleotide polymorphisms occurring in the PTC gene. Using the crystal structure of bovine rhodopsin as template, we generated the 3D structure of hTAS2R38 bitter taste receptor. We were able to map on the receptor structure the amino acids affected by the genetic polymorphisms and to propose molecular functions for two of them that explained the emergence of the nontaster trait. We used molecular docking simulations to find that phenylthiocarbamide exhibited a higher affinity for the target receptor than the structurally similar molecule 6-n-propylthiouracil, in line with recent experimental studies. A 3D model was constructed for the hTAS2R16 bitter taste receptor as well, by applying the same protocol. We found that the recently published experimental ligand binding affinity data for this receptor correlated well with the binding scores obtained from our molecular docking calculations.
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Dialysis patients generally have a poor appetite, do not enjoy eating, and complain of food, particularly protein, as being disagreeable. Twenty dialysis patients with the above symptoms were tested for taste acuity, serum zinc (Zn), Zn concentrations in hair samples (intracellular Zn), and daily caloric intake. A double-blind, cross-over study was instituted using a Zn supplement and a placebo. After supplementation with Zn, taste acuity markedly improved in 95% of patients and Zn concentrations in hair increased in 85% of patients. The patients' appetites were improved; the average caloric intake increased by 675 kcal/day, and intolerance to protein diminished. In addition 10 normal control subjects were studied pre- and post-Zn supplementation for fasting blood glucose, serum Zn levels, and hair Zn concentration. Side effects were noted, and these usually correlated with elevated serum Zn levels and were minimized or disappeared with decrease in dosage or cessation of therapy.
Subnormal plasma zinc levels and decreased zinc concentration in hair and leucocytes as well as increased plasma ammonia and ribonuclease activity in dialyzed and nondialyzed uremic patients indicate that zinc metabolism is abnormal in uremia and is not corrected by dialysis. The effect of oral supplementation with zinc acetate (12 patients) or placebo (12 patients) on the above biochemical parameters in hemodialysis patients was determined as a part of a double-blind study. The zinc-supplemented, but not the placebo, group demonstrated significant increases in mean (+/- SD), plasma zinc (80 +/- 9 to 110 +/- 14, micrograms/dl), leucocyte zinc (56 +/- 13 to 1098 +/- 18, micrograms/10(10) cells), hair zinc (140 +/- 12 to 190 +/- 16 micrograms/g), and decreases in plasma ammonia (76 +/- 10 to 40 +/- 6 micrograms/dl) and plasma ribonuclease activity (1.49 +/- 0.08 to 0.78 +/- 0.10, OD/min/ml). Abnormalities of taste and sexual function improved significantly in patients receiving zinc but not in those on placebo therapy. These improvements in biochemical as well as clinical parameters confirm and extend our earlier observations of improvement in taste and sexual function after zinc supplementation. Together, they suggest that zinc deficiency is a complicating feature of uremia and can be corrected by oral zinc supplementation.
It is difficult to determine the reason why a patient complains of a bitter taste when their mouth is empty. We examined a new diagnostic test using a bitterness masking substance. The bitterness masking substance, 'Benecoat BMI-60' (hereafter BMI-60), is a masking substance specific to the taste cells' bitterness receptors. After patients gargled with BMI-60 solutions, the phantom sensation of bitterness was masked in some patients, but was not masked in others. Bitter substances in saliva seemed to be masked by BMI-60, but bitterness did not seem to be masked when the locus of the phantom sensation was within the peripheral nerve and/or the brain. The bitterness masking test is useful for diagnosis of the phantom sensation of bitter taste.
Chlorhexidine, a bitter bis-biguanide antiseptic, is the only known blocker of the human salty taste. In order to characterize the effects of chlorhexidine on stimulus identification, taste confusion matrix (TCM) performance was measured for subjects treated with 1.34 mM chlorhexidine gluconate (n = 9) and water controls (n = 9). Ten stimuli [water, 0.1 M NaCl, 0.1 M KCl, 0.1 mM quinine-HCl (QHCl), 0.1 M monosodium glutamate (MSG), 3 mM citric acid, 0.3 M sucrose and mixtures of NaCl, QHCl and citric acid with sucrose] were presented in 10 replicates for identification from a list of 10 stimulus names. T(10), a measure of performance consistency from information theory, was lower for chlorhexidine-treated subjects (2.02 +/- 0.11 bits) than controls (2.73 +/- 0.11 bits) (P < 0.0001). T(2), an indirect measure of pairwise stimulus discrimination, approached chance levels (0.40 bit) in chlorhexidine-treated subjects for all possible pairs of NaCl, KCl, QHCl and water, as well as pairs composed of sucrose and the NaCl-sucrose and quinine-sucrose mixtures. In controls T(2) values approached perfect scores (1.00 bit) for all stimulus pairs except NaCl-KCl and NaCl-MSG. The results demonstrate a decreased ability to identify taste stimuli that is consistent with alterations in the ability of stimuli to elicit salty and bitter taste perceptions. As a selective, effective, persistent and reversible blocker of taste perceptions, chlorhexidine should prove useful in defining taste mechanisms in humans.
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Taste thresholds are known to rise with age, but the status of suprathreshold sensations is less clear. The present study assessed the perceived intensities of sodium chloride, sucrose, citric acid, and quinine hydrochloride with the method of magnitude matching. This method takes advantage of participants' ability to judge sensations from two sensory continua (in this case taste intensity and loudness) on a common intensity scale, in effect, matching them. Elderly and young adults matched most of the moderate and strong tastes to the same loudnesses. If the sounds were equivalently loud to elderly and young adults, then these results would mean that moderate and strong tastes were also equivalently strong, that is, taste sensation had not faded for our elderly adults. Water and dilute taste solutions were matched to louder sounds by elderly than young participants. This may reflect the presence of a mild dysgeusia (background taste).
Studies in several laboratories have shown that nutritional Zn deficiency in the rat causes a reduction in the activity of certain Zn-dependent enzymes in kidney, intestine, pancreas, etc. The present report deals with the effects of Zn-deficiency on submandibular gland of the rat. For the sake of comparison with previous studies, some assays on pancreas were included. Protein content, DNA, acid phosphatase, and acid protease activities were not affected in submandibular gland. Lactate dehydrogenase was unaffected in submandibular gland and showed increased activity in pancreas. Malate dehydrogenase was significantly decreased in both organs, the decrease being more marked in submandibular gland. Alkaline phosphatase activity in submandibular glands of control rats was about 10-fold higher than in pancreas. In the zinc-deficient rats, alkaline phosphatase was reduced to 59% of controls in the submandibular glands and to about 75% in pancreas. It is known from histochemical studies that in the submandibular gland this enzyme is confined to the myoepithelial cells. Recent studies attribute to salivary glands a role in the etiology of taste disturbances seen in clinical states of zinc deficiency. It is proposed that functional impairment of the myoepithelial cells might contribute to the disturbance of taste.
The appetite for specific foods and nutrients may be under neuroregulatory control. In animal studies, fat intake is increased by both opioids and galanin and reduced by enterostatin, whereas carbohydrate intake is increased by neuropeptide Y (NPY). However, what may be affected is the consumption of preferred foods rather than macronutrients. Fat and sugars are highly preferred whether consumed separately or as mixtures in foods. Studies suggest that sustained consumption of sugars and fats may have additional metabolic consequences; among these are neurochemical changes in brain sites involved in feeding and reward, some of which are also affected by drugs of abuse. Furthermore, the consumption of fats and sugars alters tissue expression of uncoupling proteins, which are also influenced by neuroregulatory peptides and may be markers of energy expenditure. These data suggest that these palatable nutrients may influence energy expenditure through changes in central neuropeptide activity. Fats and sugars could affect central reward systems, thereby increasing food intake, and might have an additional effect on energy expenditure. Such palatable substances may contribute to the observed increase in the body weight of populations from affluent societies during the past few decades.
Alterations in taste can occur as a result of cancer, cancer treatment, and from a variety of other causes. Cancer patients frequently experience taste alterations, which often go undetected in the clinical setting. This case presentation depicts a 90-year-old client with end-stage pancreatic cancer undergoing chemotherapy treatment with gemcitabine. The symptomatology of taste changes is described. Etiology and rationale for taste changes is presented for the cancer patient population, and for the general population. Review of the cancer literature, research instruments, and goals/outcomes are discussed. The author determined that interventional studies are lacking, and research is needed.
The use of an experimental liposoluble contrast agent-Ethiodized Oil Emulsion 13 (EOE 13)--is described in hepatic computed tomography (CT) of 23 oncologic patients. Without exception, all the hepatic metastases were better delineated in the EOE 13 enhanced scans. The postcontrast scans also detected an increased number of lesions but not all were malignant. There is no specificity to the increased lesion detection. Various splenic abnormalities were detected. Very few minor side effects and no major side effects were caused by the contrast media. We feel that with time, hepatic specific agents such as EOE 13 will become the contrast media of choice in hepatic CT examinations. Also, CT with hepatic specific agents may become the preoperative examination of choice in candidates for partial hepatectomy.
Zopiclone (7.5 mg), a cyclopyrrolone derivative with a 6.5 h half-life, and flurazepam (30 mg) were compared to placebo in a randomized double-blind study involving 36 adult patients suffering from insomnia. All previous psychotropic drugs were discontinued 1 week prior to the study. During 4 weeks, 12 patients received zopiclone, 12 flurazepam and the others placebo. Thereafter, all patients received single-blind placebo for 3 nights. Rapidity of sleep onset, sleep duration, frequency of nocturnal awakenings, psychomotor coordination and side-effects were assessed daily with a questionnaire and a symptom checklist. The results of the study suggest that zopiclone 7.5 mg was at least as potent as flurazepam 30 mg in inducing and maintaining sleep. Both drugs maintained their efficacy during the 4 weeks of treatment. However, the two drugs differed in that flurazepam impaired psychomotor coordination whereas zopiclone did not demonstrate daytime protracted effects on psychomotor performance. Upon discontinuation of drug treatment, score values of the different sleep parameters under study returned to the baseline values. Side-effects were mild and consistent with earlier studies.
Laser-assisted uvulopalatoplasty (LAUP) has become a widely used procedure for the treatment of snoring and mild sleep apnea in the United States. Between July 1993 and December 1994, the authors of this study prospectively evaluated 541 consecutive patients referred to their hospital for possible LAUP to treat loud disruptive snoring. Of the 541 patients, 275 patients had a total of 754 LAUP procedures. There were 26 complications (3.45%). These complications included postoperative hemorrhage in 16 patients (2.12%), local infection in 4 patients (0.53%), temporary palatal incompetence in 4 patients (0.53% , and temporary loss of taste in 2 patients (0.27%). None of the 16 patients with postoperative hemorrhage required a blood transfusion. Only 10 patients (1.3%) had hemorrhage that required medical attention; in the other patients, the bleeding stopped spontaneously. There were no cases of hypernasal speech, permanent palatal incompetence, nasopharyngeal stenosis, airway compromise, or death.
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We describe two patients who had Rocky Mountain spotted fever after they were admitted to the hospital for emergency and elective surgical procedures. We initially thought one patient had a hospital-acquired infection; the correct diagnosis was deduced from epidemiologic clues elicited by consultants. These two cases were also unusual in that one patient had a recurrent rash after an abbreviated course of low-dose doxycycline therapy and the other patient had transient and self-limiting postinfectious polyneuropathy. These cases illustrate that community-acquired infection with Rickettsia rickettsii can occur simultaneously with other disease processes and sometimes mimic a nosocomial infection.