Investigation of morphological changes in absorptive cells in young adult and infant mice fed different amounts of iron for a long-term

The changes in fine structure of the intestinal tract in young adult (4 week-old) and infant (2 week-old) mice fed a diet containing different amounts of iron salt (Fe-0, Fe-2.5, Fe-25: 0, 2.5 and 25 mg Fe/100 g diet, respectively) for a long-term (1 or 2 weeks) were investigated. The hepatic iron levels in infant mice fed Fe-25 for 2 weeks were significantly higher than those observed after 1 week of feeding, but there was no such increase in young adult mice during the feeding period. Observations of fine structure indicated typical signs of impairment of enterocytes due to excess iron such as the opening of intercellular junctions between adjacent epithelial cells and the marked appearance of eosinophilic leukocytes outside the basement membrane in young adult and infant mice fed Fe-25. The frequency of the opening in intercellular junctions increased in young adult mice fed Fe-25 for 2 weeks, but decreased in infant mice. On the contrary, under iron-deficient conditions, the frequency in infant mice was higher than that in young adult mice. The appearance of eosinophilic leukocytes indicated that some immunological reaction was elicited in both groups of mice fed Fe-25 for 2 weeks.

A dynamic neural network with temporal coding and functional connectivity

A neural network model capable of altering its pattern classifying properties by program input is proposed. Here the "program input" is another source of input besides the pattern input. Unlike most neural network models, this model runs as a deterministic point process of spikes in continuous time; connections among neurons have finite delays, which are set randomly according to a normal distribution. Furthermore, this model utilizes functional connectivity which is dynamic connectivity among neurons peculiar to temporal-coding neural networks with short neuronal decay time constants. Computer simulation of the proposed network has been performed, and the results are considered in light of experimental results shown recently for correlated firings of neurons.

Silver-stained nucleolar organizer regions in hypertrophic and keloid scars

Silver-stained nucleolar organizer regions (AgNORs) have been widely used as a marker of cellular activity and proliferation. In a retrospective study, we investigated the potential value of AgNORs in 12 hypertrophic and 24 keloid scar tissues. Ten normal skin tissues served as controls. A standard silver-staining method was used, and the mean AgNOR count of dermal fibroblastic cells in each tissue was determined. In normal skin, the mean AgNOR count of dermal fibroblasts was 1.79+/-0.55, whereas fibroblastic cells in hypertrophic and keloid scars had mean AgNOR counts of 3.18+/-0.56 and 5.10+/-0.97, respectively. There was a statistically significant difference between the mean AgNOR counts of fibroblastic cells from normal skin, hypertrophic scar, and keloid scar [one-factor analysis of variance (ANOVA), p < 0.0001]. Our findings suggest that AgNOR count may be a useful marker for assessment of fibroblastic cell activity in hypertrophic and keloid scars, which may have potential value for histologic and biologic characterization of the two lesions.

Inhibitory effects of insulin on intracellular calcium and aggregatory response of platelets are impaired in hypertensive subjects with insulin resistance

To determine the effects of insulin on intracellular calcium and platelet aggregatory responses in hypertensive subjects with insulin resistance, we measured insulin sensitivity in terms of glucose disposal rate (GDR) by the hyperinsulinemic euglycemic clamp technique (GC) in 14 non-diabetic untreated hypertensive subjects, and determined basal ([Ca2+]i) and thrombin-stimulated (T-[Ca2+]i) platelet-free calcium concentrations and thrombin-stimulated platelet aggregatory response (AG) before (PRE[Ca2+]i, T-PRE[Ca2+]i, and PRE AG, respectively) and during (POST[Ca2+]i, T-POST[Ca2+]i, and POST AG, respectively) GC. As a control for GC, vehicle (normal saline) was infused on another day. No significant difference was observed between PRE[Ca2+]i and POST[Ca2+]i, T-PRE[Ca2+]i and T-POST[Ca2+]i, or PRE AG and POST AG, GDR inversely correlated with delta[Ca2+]i (POST [Ca2+]i-PRE[Ca2+]i, r = -0.75, p < 0.02), delta T-[Ca2+]i, (T-POST[Ca2+]i-T-PRE[Ca2+]i, r = -0.63, p < 0.02) and delta AG (POST AG-PRE AG, r = -0.67, p < 0.01). No significant changes were observed in these variables during vehicle infusion. [Ca2+]i, T-[Ca2+]i, and AG decreased during GC as compared with baseline in hypertensive subjects with normal insulin sensitivity, but were unchanged in those with insulin resistance, suggesting that the vasodilatory and anti-platelet aggregatory effects of insulin are impaired in patients with insulin-resistant hypertension.

Mucin carbohydrate antigens (T, Tn, and sialyl-Tn) in human ovarian carcinomas: relationship with histopathology and prognosis

Altered glycosylation of mucins leading to the expression of T, Tn, and sialyl-Tn antigens has been shown in ovarian carcinoma, but its relationship with prognosis is still unclear. We investigated immunohistochemically the expression of these antigens in 38 (17 serous and 21 mucinous) ovarian carcinomas to assess their potential prognostic value as compared with stage of disease, histopathology of tumors, and survival time of patients. Eight benign ovarian tumors (four serous and four mucinous), and four normal ovarian tissues also were studied. Of the 38 carcinomas, 25 (66%) expressed T, 27 (71%) expressed Tn, and 33 (87%) expressed sialyl-Tn antigens. Most cases (83%) expressed two or all of the three types of antigens simultaneously. Normal ovarian epithelia showed no staining for these antigens, and benign ovarian tumors were either negative or occasionally expressed weak staining in less than 25% of epithelial cell areas. Statistical analyses showed strong associations between Tn and sialyl-Tn antigen expressions and disease stage as well as histological grade. In 19 ovarian carcinoma patients with available survival data, the overall survival times of patients with high Tn or sialyl-Tn antigen expression were significantly worse than those of the patients with negative and low expression (P < .05 and P < .01). In multivariate stepwise regression analysis, disease stage (P = .000) and Tn antigen expression (P = .02) were found to be significant independent parameters associated with the overall survival time. These findings suggest that, with exception of T antigen expression, the expression of Tn and sialyl-Tn antigens in ovarian carcinomas may provide additional prognostic information on patient outcome.

Characterization of melanosomes and melanogenesis in cells cultured from Ota's nevus

Cells from dermis and epidermis of Ota's nevus lesions were cultured to obtain the pigment producing cells that are specific epidermal and dermal melanocytes of nevus Ota. The following media were used: Eagle's minimum essential medium, fortified or not fortified with cholera toxin and phorbol ester. Both epidermal melanocytes and dermal melanocytes grew in the Eagle's minimum essential medium fortified with cholera toxin and phorbol ester. The melanocytes were characterized by 14C-tyrosine uptake and by identification of melanosomes and status of melanogenesis in comparison with those reported in dysplastic nevi and melanomas, as well as those found in Ota's nevus tissue in situ. Eumelanosomes, pheomelanosomes and secondary lysosomal melanosomes appeared in epidermal melanocytes. Pheomelanosomes and melanolysosomes, or myelinosiderosomes appeared predominantly in the dermal melanocytes. These melanosomes seemed to be related to the peculiar skin color of nevus Ota. Some of the abnormal types of melanosomes were very similar to those found in dysplastic nevi and melanomas.

[Histopathological and autoradiographical studies of experimental brain tumors after continuous local chemotherapy--acute stage in rat models]

Continuous local chemotherapy has been evaluated as being an effective administration method and as a possible adjuvant therapy in the sensitivity aspect of the cell cycle for malignant glioma. However, neurotoxicity of anti-cancer agents in the normal brain and non-effective methods for the deeper part of the tumor seem to be the most serious problems. This study was initiated to evaluate histological findings, the uptake distribution, and neurotoxicity of the continuous local administration of isotope labeled anti-cancer agents in the brain tumor of rats. The experimental brain tumor of rats and the method of continuous local chemotherapy were as follows. The tumor was produced by intracerebral inoculation of cultured cells derived from rat brain tumor induced by Rous sarcoma virus (Kumanishi et al. strain). One week later Fluorouracil (5-6-3H) (17.7 Ci/m mol) and methotrexate (L-glutamyl 3-4-3H) (41.0 Ci/m mol) were administered into the brain tumors of rats utilizing a mini osmotic pump (Alzet Model 2001), respectively. We used five rats of various groups. The rats were sacrificed at various time intervals (6 hrs, 12 hrs, 24 hrs, 48 hrs, 72 hrs and 7 days). The tumor tissues for light microscopic autoradiography were fixed in 10% formalin for 24 hours. Sections for the light microscopic autoradiography were cut at 4 mu thick and coated with Sakura NR-M2 drips. Following exposure for one week at 4 degrees C, the sections were stained with Konidol X. Six hours after administration, slight radioactivity was distributed in the subarachnoid space and subpial brain tissue in the vicinity of the inserted tube. Twenty-four hours after administration, high radioactivity was clearly present in many tumor cells and phagocytes at the tube tip, but no radioactivity was observed in the deeper part of the tumor or normal brain tissue. In the vicinity of necrosis foci, acute toxic inflammation was also observed. In conclusion, this experimental study shows that these anti-cancer agents are capable of direct penetration into the neoplastic cells of an intracerebral tumor following continuous local administration. However, necrotic foci were small in size. The most serious side effect seemed to be the presence of acute toxic inflammation in the vicinity of the necrotic foci.

Prognostic value of proliferative activity of ovarian carcinoma as revealed by PCNA and AgNOR analyses

Proliferative activity of a malignant tumor is known to reflect its biologic aggressiveness. Proliferating cell nuclear antigen (PCNA) is a marker of cellular proliferation, and silver-stained nucleolar organizer regions (AgNORs) have been shown to correlate with ploidy and proliferative activity of cells depending on the method of assessment; the mean number of AgNORs per nucleus reflects ploidy, whereas the mean percentage of nuclei with five or more AgNORs per nucleus indicates proliferative activity. In ovarian carcinoma, the prognostic value of these markers has not been well defined. We studied PCNA expression and the AgNOR count in 43 ovarian carcinomas (25 serous, 13 mucinous, and 5 clear cell types) to assess their potential prognostic significance compared with the stage of disease and histopathologic features of the tumors. Eight benign (four serous and four mucinous) and six normal ovarian tissues were also evaluated. A standard colloidal silver staining and an immunohistochemical method were used. The mean percentage of PCNA positivity (PCNA index), the mean number of AgNORs per nucleus (mAgNOR), and the mean percentage of nuclei with more than five AgNORs per nucleus (pAgNOR) for each lesion were determined. In univariable analysis, PCNA indexes and mAgNOR and pAgNOR values were significantly higher in benign ovarian tumors compared with normal ovarian tissues and in adenocarcinomas compared with benign ovarian tumors. In multivariable analysis, PCNA indexes were significantly associated with histologic grade (P=.003), whereas associations of mAgNOR and pAgNOR values were highly significant with both histologic grade and disease stage (P=.0001). Histologic grade, but not subtype, was also associated with disease stage at a significant level (P=.008). Our findings indicate that differences in biologic behavior of ovarian carcinomas may, in part, be defined by differences in their ploidy and proliferative activity, and that whereas PCNA expression is of limited value, assessment of AgNORs holds promise in providing valuable prognostic information on the biologic behavior of the tumors.

A clinicopathological study of malignant glioma done after local administration of chemotherapeutic agents

Light and electron microscopic studies on tumor tissue from 5 autopsied and 7 rebiopsied patients with malignant glioma after receiving intratumor administration of anti-neoplastic agents were made. Four patients were correlated with their serial MRI. After craniotomy 0.5 mg of adriamycin was administered using an Ommaya reservoir into the tumor bed. Light microscopy of the recurrent tumor and adjacent necrotic tissue revealed massive coagulation necrosis which was aspirated into the tip of the Ommaya tube. Around the massive coagulation necrosis and cystic cavity, abundant reactive collagenous tissues, gliomesenchymal tissue, infiltrating lymphocytes, and a small amount of foreign body giant cells were found concomitantly with organized necrotic tissue. The electron microscopic study of the above mentioned tissue showed deposits of lipofuscin, lipid droplets, lysosomes in the tissue as well as abundant disintegrated myelin figures and fibrous strands. Furthermore, marked histological necrosis was found mainly at the tip of the Ommaya tube. These morphological findings corresponded to the high signal intensity areas on the gadolinium-enhanced T1-weighted MRI. These facts may indicate that the antineoplastic agents administered directly to a tumor per se cause morphological alternations. Moreover, these facts may suggest a therapeutic effect in the residual tumor cells which would be facilitated by formation of coagulation necrosis and collagenous tissue.

Pruning of rat cortical taste neurons by an artificial neural network model

1. Taste qualities are believed to be coded in the activity of ensembles of taste neurons. However, it is not clear whether all neurons are equally responsible for coding. To clarify the point, the relative contribution of each taste neuron to coding needs to be assessed. 2. We constructed simple three-layer neural networks with input units representing cortical taste neurons of the rat. The networks were trained by the back-propagation learning algorithm to classify the neural response patterns to the basic taste stimuli (sucrose, HCl, quinine hydrochloride, and NaCl). The networks had four output units representing the basic taste qualities, the values of which provide a measure for similarity of test stimuli (salts, tartaric acid, and umami substances) to the basic taste stimuli. 3. Trained networks discriminated the response patterns to the test stimuli in a plausible manner in light of previous physiological and psychological experiments. Profiles of output values of the networks paralleled those of across-neuron correlations with respect to the highest or second-highest values in the profiles. 4. We evaluated relative contributions of input units to the taste discrimination of the network by examining their significance Sj, which is defined as the sum of the absolute values of the connection weights from the jth input unit to the hidden layer. When the input units with weaker connection weights (e.g., 15 of 39 input units) were "pruned" from the trained network, the ability of the network to discriminate the basic taste qualities as well as other test stimuli was not greatly affected. On the other hand, the taste discrimination of the network progressively deteriorated much more rapidly with pruning of input units with stronger connection weights. 5. These results suggest that cortical taste neurons differentially contribute to the coding of taste qualities. The pruning technique may enable the evaluation of a given taste neuron in terms of its relative contribution to the coding, with Sj providing a quantitative measure for such evaluation.

Electron microscopical studies of the cell population in nasal secretions

The purpose of this study is to identify the cell types and ultrastructural changes of the cells in nasal secretions, and to understand the pathology of allergic and infectious rhinitis. Nasal secretions from 20 patients with allergic rhinitis and 15 patients with infectious rhinitis have been observed by transmission electron microscopy. The cell population of the allergic group consists of (in order of predominance): epithelial cells, eosinophils, neutrophils, lymphocytes, basophilic cells (basophil leukocytes and mast cells), and macrophages. In the infectious group the population contains: neutrophils, epithelial cells, macrophages, and lymphocytes. Marked degranulation has been observed in the granules of eosinophils in allergic nasal secretions together with granule fusion, vacuolation, and signs of phagocytosis. Increased numbers of basophil leukocytes and mast cells are also a feature of the allergic nasal secretion. Degranulation of neutrophils is markedly increased in the infectious group as compared to the allergic group. Clustered epithelial cells are observed in the allergic group more often than in the infectious group. Four types of lymphocytes with different morphological features are observed in both groups, i.e. small lymphocyte, T-lymphocyte-like cells, large granular lymphocyte-like cells, and plasma cells. The results of the present study show special ultrastructural characteristics in the cell population of allergic nasal secretions, i.e., an increase in the number of degranulated eosinophils and basophilic cells, clustered epithelial cells, and large granular lymphocytes, while an increase in degranulated neutrophils and macrophages with marked phagocytosis are characteristic for infectious nasal secretions.

Synthetic study of 2-[(6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9- yl)-sulfinyl]-1H-benzimidazole analogs and their biological properties as novel proton pump inhibitors

A series of 2-[(cycloalka[b]pyridinyl)sulfinyl]-1H-benzimidazoles (11) was synthesized and tested for antisecretory activity against pentagastrin-induced gastric acid secretion in rats. A novel benzimidazole derivative containing a cyclohepta[b]pyridine moiety was found to be the most potent among the congeners, which included five- to eight-membered cycloalka[b]pyridine ring systems. Some 2-[(6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin-9-yl)sulfinyl]-1H- benzimidazole analogs (14) with various substituents on the aromatic rings showed superior properties to omeprazole (1) in biological examinations in vivo. A diastereoisomer, TY-11345 (28Ba), was selected as a promising agent for further evaluation.

Nizofenone, a neuroprotective drug, suppresses glutamate release and lactate accumulation

It was investigated whether nizofenone, 2'-chloro-2-(2-diethylaminomethyl-1- imidazolyl)-5-nitrobenzophenone fumarate, shows neuroprotective effect by inhibiting glutamate release and lactate accumulation in rats. Nizofenone (10 mg/kg i.p.) significantly inhibited neuronal cell death in the hippocampus CA1 pyramidal cells 7 days after 15 min of ischemia caused by 4-vessel occlusion. The extracellular level of glutamate and lactate increased in the hippocampus during ischemia. Upon reperfusion, the glutamate level decreased rapidly but, in contrast, the lactate level increased further and reached a maximum at 15 min following reperfusion. Nizofenone (10 mg/kg i.p.) completely inhibited the ischemic glutamate increase and post-ischemic lactate increase. These results suggest that the inhibition of ischemic release of glutamate and post-ischemic accumulation of lactate could contribute greatly to the neuroprotective effect of nizofenone.

[Interleukin-1 in cancer therapy]

The therapeutic potentials of interleukin-1 (IL-1) in the cancer therapy are supposed to be; 1) anti-tumor activity, 2) immunostimulating activity, and 3) hematopoietic activity. We observed that IL-1 beta revealed a directly cytostatic activity to certain tumor cells in vitro. Intratumoral or subcutaneous injection of IL-1 beta caused a complete regression and lifespan elongation of tumor-bearing mice by augmenting of the anti-tumor effects mediated by host immune responses indirectly. We have observed IL-1 beta to accelerate the recovery of the numbers of granulocytes and platelets by inducing the production of colony stimulating factors, and by stimulating the hemopoietic progenitor cells. In the phase II clinical study, IL-1 beta was proved to be effective against cutaneous T cell lymphoma (CTCL). In the hematopoietic stimulating activity of IL-1 beta, it was reported in many clinical cases that IL-1 beta accelerated the recovery of the numbers of granulocytes and platelets in myelosuppressed patients.

Effects of NG-monomethyl-L-arginine, indomethacin, and aspirin on the vasodepressor response to low doses of endothelin-1 and endothelin-3 in rats

Low doses (< or = 100 pmol/kg) of endothelin-1 (ET-1) and endothelin-3 (ET-3) elicited a fall in mean arterial pressure (MAP) and a dose-related reduction in hindquarter vascular resistance in anesthetized rats. The depressor response to low doses of ET-1 or ET-3 was short-lived (about 10 sec) and reversible. High doses (> or = 200 pmol/kg) of ET-1 and ET-3 elicited a biphasic response; an initial fall in MAP followed by a gradual increase in MAP. The pressor response to large doses of ET-3 was less than that to large doses of ET-1. On the other hand, the depressor response to low doses of ET-3 was similar to that to low doses of ET-1. Both ET-1 and ET-3 at low doses exhibited primarily a vasodilatory activity. Pretreatment with NG-monomethyl-L-arginine (L-NMMA), a compound that inhibits nitric oxide (NO) production by endothelial cells, attenuated the hypotensive and hindquarter vasodilating effects of low doses of these isopeptides, indicating that the hindquarter vasodilating responses to these peptides depend upon the release of NO from endothelial cells. On the other hand, pretreatment with either aspirin or indomethacin did not alter the hypotensive or the hindquarter vasodilating effects of either ET-1 or ET-3, indicating that cyclooxygenase products may not be involved in the vasodepressive mechanisms of these peptides. L-NMMA attenuated the vasodilating effects of these peptides, but did not completely inhibit the response, suggesting that NO production by endothelial cells plays only a partial role in the vasodilation of ET in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Doxazosin improves insulin sensitivity in hypertensive patients

Insulin sensitivity in terms of glucose disposal rate was measured by the hyperinsulinemic/euglycemic clamp technique in 10 hypertensive patients and 7 normotensive control subjects before and after 12 weeks of doxazosin therapy. Supine blood pressure fell significantly, from 150/98 mmHg before treatment to 136/90 mmHg after treatment (systolic P < 0.001/diastolic P < 0.01). The average dose of doxazosin at the end of the study was 3.3 +/- 0.4 mg/day. The glucose disposal rate during the last 30 minutes of the glucose clamp procedure was significantly increased, from 5.8 +/- 0.7 mg/kg/min before to 7.8 +/- 0.7 mg/kg/min after treatment (P < 0.02). Insulin sensitivity was 8.7 +/- 0.4 mg/kg/min in the normotensive subjects, which represented a significant difference when compared with that of the hypertensive subjects before treatment (P < 0.01). Steady-state serum insulin concentrations, as measured during the glucose clamp procedure, were 172 +/- 10.4 microU/ml before and 176 +/- 13.5 microU/ml after doxazosin treatment; these levels were significantly higher than the 137 +/- 7.0 microU/ml reading obtained in the normotensive subjects (P < 0.05). Study results show that hypertensive patients tend to be insulin resistant and that treatment with doxazosin improves insulin sensitivity.

Biochemical and pharmacological properties of a newly synthesized proton pump (H+/K(+)-ATPase) inhibitor, TY-11345 in experimental animals

We investigated the effects of the newly synthesized proton pump inhibitor TY-11345, (+/-)-2-[(4-methoxy-6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridin- 9-yl)sulfinyl]-1H-benzimidazole sodium salt, on gastric mucosal proton pump (H+/K(+)-ATPase) activity, gastric acid secretion and gastro-duodenal lesions in experimental animals. TY-11345 potently inhibited H+/K(+)-ATPase activity in isolated rabbit gastric mucosal microsomes; and the inhibitory effect was enhanced under weak acid conditions, the IC50 (concentrations that inhibit the enzyme activity by 50%) being 5.8 microM and 9.9 microM at pH 6.0 and pH 7.4, respectively. In Ghosh & Schild rats, intravenous injection of TY-11345 significantly inhibited gastric acid secretion stimulated by tetragastrin; the effect of TY-11345 was twice as potent as that of omeprazole. In pylorus ligated rats, TY-11345 inhibited basal gastric acid secretion by both the intraduodenal and oral routes, with ED50 values of 1.2 and 4.0 mg/kg, respectively. These effects were 9 and 5 times more potent than those of omeprazole, respectively. Moreover, the antisecretory effect of TY-11345 persisted for more than 24 hr in pylorus ligated rats. In experimental ulcer models, TY-11345 prevented the formation of water-immersion stress, ethanol or indomethacin-induced gastric lesions and mepirizole-induced duodenal lesions in rats. The antiulcer effects of TY-11345 were 3 to 15 times more potent than those of omeprazole. These results suggest that TY-11345 has potent antisecretory and antiulcer effects which are exerted by suppression of H+/K(+)-ATPase activity in gastric parietal cells, so that TY-11345 should be useful for the clinical treatment of peptic ulcer diseases.

Purification and characterization of recombinant human macrophage colony-stimulating factor expressed in Chinese hamster ovary cells

We expressed human macrophage colony-stimulating factor (M-CSF) in Chinese hamster ovary (CHO) cells by introducing an expression plasmid coding for a 554-amino-acid M-CSF precursor and dihydrofolate reductase (DHFR) gene, and by amplifying the sequence. A cell line was obtained that secreted approximately 200,000 units/ml after 6 days in culture. The expressed recombinant human M-CSF (rhM-CSF) primarily consisted of two molecular species, a main 80-90 kD M-CSF as a homodimer and a molecular form higher than 150 kD. Purification of a main rhM-CSF gave an apparently homogeneous protein disulfide-bonded from 42-kD subunits, but one of the purified rhM-CSFs was composed of two subunit species with molecular masses of 44 and 42 kD. These purified rhM-CSFs had substantially the same specific activity (1 to 4 x 10(7) units/mg protein). Deglycosylation experiments with the latter rhM-CSF using chemical (trifluoromethanesulfonic acid) and enzymatic methods found a terminal neuraminic acid in addition to N- and O-glycosylation, but the two subunit species did not coalesce into a single molecule.

Application of corrosion cast method for scanning electron microscopic observation of mouse embryo vasculature

We described a method for making vascular corrosion casts of mouse embryos and applied it to study the vasculature of the whole body mouse embryo at 13.5 days (body length 9-11 mm) to 18.5 days (body length 18-23 mm), as well as that of its respective organs. The Mercox resin was perfused via the umbilical vessels using a special needle made by pulling the hematocrit tube (caliber 100-200 microns). The specimens were treated with 10% NaOH, rinsed, dried, coated with gold and observed under a scanning electron microscope. Visceral organs of a 13.5 day embryo were rather immature, but the liver vasculature was relatively well developed. In a 15.5 day embryo, the whole body vasculature was relatively well developed and the features of respective organs could be identified. In a 18.5 day embryo, almost all organs and extremities were well developed, but sensory organs in some parts showed immature development.

A novel method to analyse response patterns of taste neurons by artificial neural networks

Despite several notions on the gustatory code proposed over three decades, investigators have not yet reached a consensus. This paper describes a new approach to analyse gustatory neural activities. Three-layer neural networks were trained by the back-propagation learning algorithm, to classify the neural response patterns to four basic taste qualities. The discrimination by the trained networks on taste qualities in the response patterns of rat chorda tympani fibres (CT) and cortical taste neurons (CN) was consistent both with the correlation analysis and with behavioural experiments. By examining the connection weights of each neuron, some input neurons representing CN were 'pruned' without deteriorating the ability of the network to discriminate taste. This characteristic of the network is contrary to a previous hypothesis, that taste neurons are of equal importance in the neural coding.