Drinking Ice-Cold Water Reduces the Severity of Anticancer Drug-Induced Taste Dysfunction in Mice

Taste disorders are common adverse effects of cancer chemotherapy that can reduce quality of life and impair nutritional status. However, the molecular mechanisms underlying chemotherapy-induced taste disorders remain largely unknown. Furthermore, there are no effective preventive measures for chemotherapy-induced taste disorders. We investigated the effects of a combination of three anticancer drugs (TPF: docetaxel, cisplatin and 5-fluorouracil) on the structure and function of mouse taste tissues and examined whether the drinking of ice-cold water after TPF administration would attenuate these effects. TPF administration significantly increased the number of cells expressing apoptotic and proliferative markers. Furthermore, TPF administration significantly reduced the number of cells expressing taste cell markers and the magnitudes of the responses of taste nerves to tastants. The above results suggest that anticancer drug-induced taste dysfunction may be due to a reduction in the number of taste cells expressing taste-related molecules. The suppressive effects of TPF on taste cell marker expression and taste perception were reduced by the drinking of ice-cold water. We speculate that oral cryotherapy with an ice cube might be useful for prophylaxis against anticancer drug-induced taste disorders in humans.

Identifying Treatments for Taste and Smell Disorders: Gaps and Opportunities

The chemical senses of taste and smell play a vital role in conveying information about ourselves and our environment. Tastes and smells can warn against danger and also contribute to the daily enjoyment of food, friends and family, and our surroundings. Over 12% of the US population is estimated to experience taste and smell (chemosensory) dysfunction. Yet, despite this high prevalence, long-term, effective treatments for these disorders have been largely elusive. Clinical successes in other sensory systems, including hearing and vision, have led to new hope for developments in the treatment of chemosensory disorders. To accelerate cures, we convened the "Identifying Treatments for Taste and Smell Disorders" conference, bringing together basic and translational sensory scientists, health care professionals, and patients to identify gaps in our current understanding of chemosensory dysfunction and next steps in a broad-based research strategy. Their suggestions for high-yield next steps were focused in 3 areas: increasing awareness and research capacity (e.g., patient advocacy), developing and enhancing clinical measures of taste and smell, and supporting new avenues of research into cellular and therapeutic approaches (e.g., developing human chemosensory cell lines, stem cells, and gene therapy approaches). These long-term strategies led to specific suggestions for immediate research priorities that focus on expanding our understanding of specific responses of chemosensory cells and developing valuable assays to identify and document cell development, regeneration, and function. Addressing these high-priority areas should accelerate the development of novel and effective treatments for taste and smell disorders.

Assessing taste and smell alterations in cancer patients undergoing chemotherapy according to treatment

PURPOSE

Taste and smell changes are common side effects in cancer patients undergoing chemotherapy treatments (CT). This can lead to a reduced food enjoyment and an inadequate nutrient intake with a high impact on nutritional status and quality of life. The aim of this study was to evaluate the self-reported chemosensory alterations of patients undergoing chemotherapy according to CT type.

METHODS

An observational study was conducted with 151 patients undergoing CT at Oncology Outpatient Unit from Onkologikoa Foundation. An interviewer-assisted questionnaire was designed to investigate chemosensory changes in patients undergoing CT.

RESULTS

Seventy-six percent patients reported taste disorders and 45% smell changes. Xerostomia is the most frequent symptom reported by patients receiving chemotherapy in our study (63.6%), and it is strongly associated to bad taste in mouth (OR = 5.96; CI = 2.37-14.94; p value = 0.000) and taste loss (OR = 5.96; CI = 2.37-14.94; p value = 0.000). Anthracyclines, paclitaxel, carboplatin, and docetaxel were the CT agents producing the highest taste disturbance rates. Cisplatin and 5-Fluorouracil are the CT resulting in the lowest complaints. Logistic regression revealed statistically significant associations between taste loss and carboplatin and docetaxel (OR = 3.50; CI = 1.12-10.90; p value = 0.031) and cold hypersensitivity and oxaliplatin (OR = 12.14; CI = 4.18-35.25; p value = 0.000). Not only platin-based CT such as carboplatin produced dysgeusia, but also anthracyclines and paclitaxel treatments.

CONCLUSIONS

The better knowledge of taste and smell alterations according to CT type may provide valuable information for the design of new strategies to tackle CT side effects. It is important to take into account taste and smell dysfunctions and other alterations such as xerostomia together.

Electrogustometry thresholds, tongue tip vascularization, and density and morphology of the fungiform papillae in diabetes

OBJECTIVES

The aim of this study was to investigate, in parallel, changes in electrogustometric (EGM) thresholds, the morphology and density of the fungiform papillae (fPap), and the shape and density of the vessels at the tip of the human tongue in patients with diabetes mellitus (DM).

METHODOLOGY

In 36 patients (19 females, 17 males; 12 subjects with type 1 DM and 24 subjects with type 2 DM), we recorded bilateral EGM-thresholds at the areas innervated by the chorda tympani, the glossopharyngeal nerves, and the greater petrosal nerves. We examined the morphology and density of the fPap and blood vessel density and morphology at the tip of the tongue with contact endoscopy (CE). A group of 36 healthy, age-matched, non-smoking individuals served as controls.

RESULTS

The fPap density measured by CE was significantly (p < 0.05) reduced in DM compared to control groups. EGM-thresholds were significantly higher in the DM group than in the control group (p < 0.05). Gender did not have a significant impact on CE and EGM findings within the DM group. Body mass index did not significantly affect EGM-thresholds or the morphology and vascularization of fPap.

CONCLUSION

These results suggested that DM significantly reduced gustatory function, based on EGM, and impaired the gustatory anatomical structures, based on CE. Both EGM and CE may be useful in clinical settings to monitor taste disorders in patients with DM.

Defects in the peripheral taste structure and function in the MRL/lpr mouse model of autoimmune disease

While our understanding of the molecular and cellular aspects of taste reception and signaling continues to improve, the aberrations in these processes that lead to taste dysfunction remain largely unexplored. Abnormalities in taste can develop in a variety of diseases, including infections and autoimmune disorders. In this study, we used a mouse model of autoimmune disease to investigate the underlying mechanisms of taste disorders. MRL/MpJ-Fas(lpr)/J (MRL/lpr) mice develop a systemic autoimmunity with phenotypic similarities to human systemic lupus erythematosus and Sjögren's syndrome. Our results show that the taste tissues of MRL/lpr mice exhibit characteristics of inflammation, including infiltration of T lymphocytes and elevated levels of some inflammatory cytokines. Histological studies reveal that the taste buds of MRL/lpr mice are smaller than those of wild-type congenic control (MRL/+/+) mice. 5-Bromo-2'-deoxyuridine (BrdU) pulse-chase experiments show that fewer BrdU-labeled cells enter the taste buds of MRL/lpr mice, suggesting an inhibition of taste cell renewal. Real-time RT-PCR analyses show that mRNA levels of several type II taste cell markers are lower in MRL/lpr mice. Immunohistochemical analyses confirm a significant reduction in the number of gustducin-positive taste receptor cells in the taste buds of MRL/lpr mice. Furthermore, MRL/lpr mice exhibit reduced gustatory nerve responses to the bitter compound quinine and the sweet compound saccharin and reduced behavioral responses to bitter, sweet, and umami taste substances compared with controls. In contrast, their responses to salty and sour compounds are comparable to those of control mice in both nerve recording and behavioral experiments. Together, our results suggest that type II taste receptor cells, which are essential for bitter, sweet, and umami taste reception and signaling, are selectively affected in MRL/lpr mice, a model for autoimmune disease with chronic inflammation.

Taste alterations in breast and gynaecological cancer patients receiving chemotherapy: prevalence, course of severity, and quality of life correlates

BACKGROUND

Taste alterations (TAs) are frequently reported by chemotherapy patients. However, research on this topic is very scarce. The etiologies of TAs are not fully known and prevalences may vary across tumour types and chemotherapy regimens. The aim of the present study was to longitudinally investigate TAs in patients with breast cancer or gynaecological cancers receiving chemotherapy, and to provide expected values for TAs for these patient populations.

PATIENTS AND METHODS

One hundred and nine cancer patients (32.1% gynaecological cancer, 67.9% breast cancer) receiving chemotherapy at the Department for Internal Medicine of Kufstein County Hospital were consecutively included in the study. At each visit the Quality of Life Questionnaire-Core30 and a screening scale for TAs, consisting of two validated questions taken from the European Organisation for Research and Treatment of Cancer item bank was administered. Statistical analysis was performed using mixed-effect models.

RESULTS

The prevalence of TAs in breast cancer and gynaecological cancer patients receiving chemotherapy was high (76.1%). There were differences in the extent of TAs as well as in their time course across treatment groups. The lowest TAs were found in breast cancer and gynaecological cancer patients treated with gemcitabine. The highest TAs were found in breast cancer patients treated with epirubicin/docetaxel/capecitabine. The steepest increase of TAs was found in patients treated with epirubicin/docetaxel. Moreover, significant associations between TAs and appetite loss as well as fatigue were found.

CONCLUSION

The results show that TAs are an issue in breast and gynaecological cancer patients receiving different chemotherapy regimens. There is a need for a more systematic investigation of TAs in chemotherapy patients in general as well as the need to address this issue in clinical practice.

Taste disorders in Australian Aboriginal and non-Aboriginal children

AIM

To assess the prevalence and type of taste disorders in Aboriginal and non-Aboriginal children matched for age, gender and living in the same general and educational environment.

METHODS

Taste function was assessed in 432 Aboriginal (n = 166) and non-Aboriginal (n = 266) children aged 8-12 years from six public schools in a rural township using a three-choice taste identification test and a cross-sectional design.

RESULTS

The prevalence of taste disorders was very high and significantly more common in Aboriginal (20/166; 12.0%) than in non-Aboriginal (21/266; 7.9%) children. Forty-one children had quality-specific disorders, of whom 27 (65.9%) had sweet disorders. Children often had more than one quality disorder.

CONCLUSION

The prevalence of taste disorders in children was high and exceeded the level (4%) designated by the World Health Organisation as requiring immediate action by health authorities. As the cause of the disorders is unknown, there is a need for a wider investigation of the causes and the consequences.

Inflammation activates the interferon signaling pathways in taste bud cells

Patients with viral and bacterial infections or other inflammatory illnesses often experience taste dysfunctions. The agents responsible for these taste disorders are thought to be related to infection-induced inflammation, but the mechanisms are not known. As a first step in characterizing the possible role of inflammation in taste disorders, we report here evidence for the presence of interferon (IFN)-mediated signaling pathways in taste bud cells. IFN receptors, particularly the IFN-gamma receptor IFNGR1, are coexpressed with the taste cell-type markers neuronal cell adhesion molecule and alpha-gustducin, suggesting that both the taste receptor cells and synapse-forming cells in the taste bud can be stimulated by IFN. Incubation of taste bud-containing lingual epithelia with recombinant IFN-alpha and IFN-gamma triggered the IFN-mediated signaling cascades, resulting in the phosphorylation of the downstream STAT1 (signal transducer and activator of transcription protein 1) transcription factor. Intraperitoneal injection of lipopolysaccharide or polyinosinic:polycytidylic acid into mice, mimicking bacterial and viral infections, respectively, altered gene expression patterns in taste bud cells. Furthermore, the systemic administration of either IFN-alpha or IFN-gamma significantly increased the number of taste bud cells undergoing programmed cell death. These findings suggest that bacterial and viral infection-induced IFNs can act directly on taste bud cells, affecting their cellular function in taste transduction, and that IFN-induced apoptosis in taste buds may cause abnormal cell turnover and skew the representation of different taste bud cell types, leading to the development of taste disorders. To our knowledge, this is the first study providing direct evidence that inflammation can affect taste buds through cytokine signaling pathways.

Genetic and pathological taste variation: what can we learn from animal models and human disease?

The study of patients with taste disorders (i.e. 'experiments of nature') suggests that the old tongue maps (e.g. sweet on the tip, bitter on the back) that often appear in textbooks are wrong. If they were correct, severing the taste nerves that innervate the front of the tongue would result in a loss of the ability to taste sweet, etc. This does not occur. Severing these nerves has little effect on everyday taste experience because taste nerves inhibit one another. Damaging one nerve abolishes its ability to inhibit others and the release-of-inhibition compensates for the damage. There is sometimes a clinical cost for this redundancy; release-of-inhibition can produce taste phantoms. Genetic variation in taste ability occurs across and within species. For example, about 25% of humans are relatively unresponsive to a variety of sweet and bitter compounds (non-tasters) while another 25% are unusually responsive (supertasters). Supertasters have about four times as many taste buds as non-tasters and have smaller and more densely packed fungiform papillae. Since there are pain fibres associated with taste buds, supertasters are unusually responsive to the oral burn of spices.

Atypical keratosis obturans

Keratosis obturans is a rare condition characterized by the accumulation of desquamated keratin material in the bony portion of the external auditory canal. Classically, it is reported to present with severe otalgia, conductive deafness and global widening of the canal. A case of keratosis obturans is described in which the principal symptom was a metallic taste and the main finding was extensive erosion of the hypotympanum with exposure of the facial nerve and the annulus of the tympanic membrane. This presenting symptom and resorption pattern are atypical of keratosis obturans and have not been documented previously.

Confocal microscopy of the peripheral gustatory system: comparison between healthy subjects and patients suffering from taste disorders during radiochemotherapy

OBJECTIVES

Laser-scanning microscopy (LSM) was used to compare taste buds and epithelia of fungiform papillae of healthy subjects with those of patients suffering from taste disorders during/after radiochemotherapy (RCT). Aim of the study was to investigate effects responsible for taste loss at a microscopic level.

STUDY DESIGN

Prospective study.

METHODS

Data from 12 healthy subjects (mean age 52.4, SD 9.5 years) were compared with those of 12 patients (mean age 54.7, SD 8.5 years) with head and neck cancer suffering from taste disorders during RCT. Four parameters from LSM were selected for analysis: 1) distance between the pore of the taste buds of fungiform papillae and the crest of the papillary vessels; 2) epithelial cells of each taste bud at 34 mum; 3), cell density, and 4) area of the taste pore at 4 mum. These data were correlated to measures of gustatory sensitivity obtained with both the validated "taste strips" test kit and electrogustometry.

RESULTS

Patients complaining from taste disorders during RCT exhibited a significant decrease of taste function assessed with both natural and electric stimuli. In these patients, we found thicker epithelia and smaller areas of the taste pores compared with healthy subjects. In 30% of those patients, no taste pores were detectable; in deeper sections, however, normal taste buds were present.

CONCLUSIONS

In conclusion, in RCT patients with taste disorders, LSM indicates changes of epithelia of fungiform papilla but no changes of the taste bud structure. Damage of the chorda tympani nerve by scattered rays, direct or indirect mucotoxic effects of chemotherapeutic agents, and covering of taste pores by epithelial cells are likely reasons for taste loss during RCT.

Taste Disorders in Acute Stroke

Background and Purpose— The aim of the study was to assess whether and how frequently patients with acute first-ever stroke exhibit gustatory dysfunction.

Methods— We performed a 1-year prospective observational study. Gustatory function was assessed using the standardized “taste strips” test. In addition, we assessed olfactory function, swallowing, stroke location, comorbidities, and the patients’ medication.

Results— A total of 102 consecutive patients were enrolled (45 female, 57 male; mean age, 63 years); 31 of them (30%) exhibited gustatory loss and 7 (6%) had lateralized impairment of taste function. Predictors of impaired taste function were male gender ( P =0.003), high National Institutes of Health Stroke Scale (NIHSS) score at admission ( P =0.009), coexisting swallowing dysfunction ( P =0.026), and a stroke of partial anterior circulation subtype (PACS) ( P =0.008). In particular, in hypogeusic patients the lesion was most frequently localized in the frontal lobe ( P =0.009). Follow-up examinations in 14 patients indicated improvement of taste sensitivity.

Conclusion— Taste disorders after stroke are frequent. A significant association was found for male gender, high NIHSS score, swallowing disorder, and PACS, particularly in the frontal lobe. Generally, taste disorders after stroke seem to have a good prognosis.

Morphometric evaluation of the human tractus solitarius

We measured the cross-sectional area (CSA) of the human tractus solitarius (HTS) with the help of an image-analyzer system on a cross section of the upper part of the medulla oblongata in 44 Japanese cadavers (22 males and 22 females) and examined the relationship between age, sex and whether the subjects were dentulous or edentulous. The results showed no significant differences between the left and right sides of the HTS in either male or female subjects. However, the size of HTS decreased slightly with age in males but not at all in females, whereas tooth loss had a definite incidence on the size of HTS in females but not in male, as the CSA was smaller in edentulous females but not in edentulous males. This would tend to indicate that a decreases in taste function is connected with the aging process in male, and with tooth loss in females.

[Contact endoscopic quantification of fungiform papillae--correlation to taste ability?]

BACKGROUND

Besides anamnestic data and taste test, the clarification of epithelial taste disorders makes macroscopic evaluation of the surface of the tongue necessary.

METHODS

In this article the contact endoscopy is evaluated for examination of the tongue epithelium and for quantification of the fungiforme papillae. These results are related to the results of the spatial taste test (1. chemical taste test with sodium chloride in 2 different suprathreshold concentrations and sucrose in also 2 different suprathreshold concentrations; 2. electrogustometry with a bipolar electrode).

PATIENTS

In a prospective study we performed contact endoscopy in 16 healthy volunteers from ages 7 to 68 years. The subjects were divided into 2 age groups (< or = 45 years and > 45 years) and 2 papillae density groups. In 34 patients with either taste disorders of unknown cause or in patients with macroscopic changes at the tongue surface, the spatial and whole mouth taste tests and contact endoscopy were used to clarify the cause of the complaints.

RESULTS

Density and shape of the fungiform papillae as well as the shape of the subepithelial vessels of the papillae vary among the investigated human subjects in the different age groups. No correlation between intensity ratings, papillae density und age was found after stimulation with 40 % sucrose at the tongue tip in the younger age group. Stimulation of the tongue edge with 15 % sodium chloride, however, showed a relationship between the two different density groups and the different age groups.

CONCLUSIONS

The contact endoscopy allows the evaluation of the epithelium in the oral cavity. It is a nondestructive method and is additionally easy to handle, but the evaluation of the observed epithelia needs interdisciplinary co-operation with pathologists. No relevant informations are supplied in diagnostics of taste disorders.

Postoperative taste and smell deficit after upper gastrointestinal cancer surgery--an unreported complication

BACKGROUND AND OBJECTIVES

Patients undergoing upper gastrointestinal cancer surgery were noted to suffer loss of taste and/or smell, a previously unreported problem. Our aim was to investigate the extent of this phenomenon, quantify recovery time, and identify potentially associated factors.

METHODS

In this retrospective study, a postal questionnaire was sent to all patients still alive after oesophagectomy or gastrectomy, with a minimum 1-year follow-up and no clinical or radiological evidence of recurrence. Data were analysed for prevalence of deficit in relation to operation, age, sex, respiratory complications, and disease stage.

RESULTS

A total of 109/119 (92%) patients completed the questionnaire: 50 gastrectomies and 69 oesophagectomies. Ten patients were excluded with prior sensory deficit. Overall, 45/99 patients (45%) suffered deficit (M:F = 1.6:1). No association was found with type of surgery: deficits for subtotal gastrectomy, total gastrectomy, and oesophagectomy were 44, 46 and 46% respectively (chi(2) = 0.355, 2 df P > 0.5). No other parameter was associated, and full recovery occurred in 30 patients (67%) within a mean of 6 months.

CONCLUSIONS

Loss of taste and smell occurs in nearly one-half of all cases after upper gastrointestinal surgery. The pathophysiology is unknown, but it resolves in most patients within 6-12 months. This complication should be discussed as part of informed consent for patients undergoing oesophagogastric cancer surgery.

Anatomy of the tonsillar bed: topographical relationship between the palatine tonsil and the lingual branch of the glossopharyngeal nerve

Taste disturbance may result from injury to the lingual branch of the glossopharyngeal nerve (LBGN) during tonsillectomy. Because an understanding of the anatomy of this nerve is required in order to avoid injuring it, a gross, histologic anatomic study was undertaken of the topographical relationship between the LBGN and the muscle layer of the palatine tonsillar bed. Evaluation of 107 sides of 83 Japanese adult cadavers (aged 27-88 years) confirmed that the muscular composition and lamination of the tonsillar bed do not change with age or pathological conditions such as inflammation. In about a quarter (23.4%) of cases, the LBGN traveled inferior to the styloglossus muscle and lateral to the superior constrictor pharyngeal muscle over its whole course to the base of the tongue, so that the palatine tonsil was clearly separated from the LBGN. In 55.1% of cases, however, the muscle lining of the tonsillar bed was discontinuous and thin muscle bundles, derived from the stylopharyngeus, palatopharyngeus or superior constrictor pharyngeal muscle, partially covered the tonsillar capsule externally. Moreover, in 21.5% of cases the LBGN was firmly adherent to the tonsillar capsule, due to the complete absence of muscles lining the tonsillar bed. In these cases, and also probably in a similar percentage of patients undergoing tonsillectomy, taste disturbance may occur on removal of the hypertrophic tonsillar capsule. Therefore, minimal disturbance of the tonsillar bed is recommended in all cases of tonsillectomy.

[Three-dimensional analysis of human Ebner's gland]

We analyzed changes in Ebner's gland with aging by 3-dimensional analysis to determine the relationship between the gland and the sense of taste. Samples were collected from Circumvallate papillae of the tongue in autopsied cases. After dehydration, samples were embedded in paraffin and cut into slices 5 microns thick for every 100 microns. Hematoxylin-Eosin staining was done. The section was photographed in black and white and printed. Three tissues, circumvallate papillae, epithelium, and Ebner's gland were identified and traced on an OHP sheet and imput to a computer. The cubic volume of Ebner's gland was measured by Cosmozone 2SA 3-dimensional analysis software by and acinar cell occupancy I-BAS one imaging analysis. A total of 60 cases from age groups in them 30s, 40s, 50s, 60s, 70s, and 80s were used. Each group contains 5 men and 5 women. The mean cubic volume of Ebner's gland in the 30s was 67.0 mm3, in the 40s was 64.6 mm3, in the 50s was 59.8 mm3, in the 60s was 39.2 mm3, in the 70s was 33.9 mm3, and in the 80s was 30.4 mm3. Statistical analysis showed a significant difference in Ebner's gland cubic volume between age groups at p < 0.01. In acinar cell occupancIEs the coefficient of correlation was -0.858 in men and -0.838 in women with the correlation diagram showing a negative correlation. The acinar cell occupancy decreases with age for the presumed acinar cell volume in the Ebner's gland, the coefficient of correlation was -0.929 in men and -0.854 in women, with the correlation diagram showing a negative correlation. The presumed acinar cell volume decreases with age. We concluded that Ebner's gland is concerned indirectly with diminished sensitivity of the sense of taste with aging.

[Gustatory nervous pathway syndromes]

Although the lingual nerve and the chorda tympani are the components of the classic peripheral gustatory pathway, loss of taste in patients after surgery for trigeminal neuralgia supports for the existence of an accessory gustatory pathway through the trigeminal sensory root and the gasserian ganglion. Bell's palsy is the most common pathology of the peripheral gustatory pathway. The central gustatory pathway ascends from the solitary tract nucleus in the medulla up to the upper pons in the ipsilateral central tegmental tract, rather than in the medial lemniscus as proposed in the past. It is not possible to specify whether the central gustatory pathway decussates or not at the lower midbrain level. Interruption of the gustatory pathway in the brainstem usually occurs with stroke or demyelination. The thalamic gustatory relay is located in the most medial aspect of the ventroposteromedial nucleus, immediately adjacent to the somatosensory area for the oral cavity and fingers. Therefore, ageusia associated with the sensory cheiro-oral syndrome may occur with a thalamic lesion. The laterality of the gustatory representation in the thalamus remains unresolved. Studies on epileptic gustatory aura have demonstrated that the insula and the anteromedial temporal lobe are the primary and secondary gustatory cortex, respectively. Taste perception results in patients with corpus callosum section and strokes or tumors involving the insula support the hypothesis that there is a gustatory representation of both hemitongues in the left cerebral hemisphere, whereas only the right hemitongue is represented in the right hemisphere.

Cases of two patients whose food aversions disappeared following severe traumatic brain injury

Following traumatic brain injury (TBI) the complete disappearance of food aversions was observed in the cases of two patients. In one of the cases, a young female, this change in her food aversion was manifested several months after the TBI, from the time when she was able to eat normally. The other patient, a young man, exhibited the disappearance of his food aversion immediately after recovery from his unconscious state following TBI. These results indicate that the disappearance of food aversions was a consequence of TBI.

Localization of the gustatory pathway in the human midbrain

The localization of the secondary gustatory pathway in the human brainstem still remains uncertain. Here we report two patients with small vascular lesions in the unilateral midbrain tegmentum who presented with taste disturbance on the ipsilateral side of the tongue. In both cases, the dorsomedial mesencephalic tegmental region lateral to the oculomotor nucleus, including the central tegmental tract and the ventral part of the periaqueductal gray, was involved commonly in the lesions. The secondary gustatory pathway arising from the nucleus of the solitary tract appears to run rostrally, without crossing, to the ipsilateral thalamic nucleus through the dorsomedial part of the tegmental region at the rostral level of the midbrain.

[Incidence of taste disorders following tonsillectomy]

Due to their course in the pharyngeal space, the gustatory nerves can be damaged during tonsillectomy. We describe 150 patients, the results of gustatory tests and the frequency of disorders of taste.

Electron microscopic observation of vallate taste buds of zinc-deficient rats with taste disturbance

Henkin et al. (1975) reported that there is a loss of the dense substance in the taste pore region, a loss of microvilli and a decrease of dark granules and microvacuolation in the taste pore buds of patients who complain of taste disturbance. In our experiment, we prepared artificially zinc-deficient rats by feeding a zinc-deficient diet and observed the same results in the taste buds of zinc-deficient rats with taste disturbance.

Assessment of taste disorders in rats by simultaneous study of the two-bottle preference test and abnormal ingestive behavior

Taste disorders were produced in rats by the administration of a zinc-deficient diet and assessed by two methods, i.e., observations of the subjects' behavior in terms of the two-bottle preference test and of their ingestive behavior in terms of taste differentiation. The findings of the two tests were compared, revealing a high degree of agreement. The results indicate that reliable data can be obtained from the two-bottle preference test, an examination procedure extensively applied to the study of taste disorders, as well as from observation of the rats' ingestive behavior. Thus, both methods can be used in parallel for assessing or confirming taste disorders in rats.

Primary pontine hemorrhage and gustatory disturbance: clinicoanatomic study

A clinicoanatomic study of 12 patients with tegmental-type primary pontine hemorrhage proved the presence of a gustatory disturbance among other clinical symptoms on the same side of the tongue as that of the pontine lesion, and suggested the secondary pathway of gustatory sensation from the solitary tract nucleus ascends without decussation in the homolateral pontine tegmentum. These results contradict textbook descriptions regarding the human secondary gustatory pathway.