Inhibition of the Raf-1 kinase by cyclic AMP agonists causes apoptosis of v-abl-transformed cells.

Here we investigate the role of the Raf-1 kinase in transformation by the v-abl oncogene. Raf-1 can activate a transforming signalling cascade comprising the consecutive activation of Mek and extracellular-signal-regulated kinases (Erks). In v-abl-transformed cells the endogenous Raf-1 protein was phosphorylated on tyrosine and displayed high constitutive kinase activity. The activities of the Erks were constitutively elevated in both v-raf- and v-abl-transformed cells. In both cell types the activities of Raf-1 and v-raf were almost completely suppressed after activation of the cyclic AMP-dependent kinase (protein kinase A [PKA]), whereas the v-abl kinase was not affected. Raf inhibition substantially diminished the activities of Erks in v-raf-transformed cells but not in v-abl-transformed cells, indicating that v-abl can activate Erks by a Raf-1-independent pathway. PKA activation induced apoptosis in v-abl-transformed cells while reverting v-raf transformation without severe cytopathic effects. Overexpression of Raf-1 in v-abl-transformed cells partially protected the cells from apoptosis induced by PKA activation. In contrast to PKA activators, a Mek inhibitor did not induce apoptosis. The diverse biological responses correlated with the status of c-myc gene expression. v-abl-transformed cells featured high constitutive levels of expression of c-myc, which were not reduced following PKA activation. Myc activation has been previously shown to be essential for transformation by oncogenic Abl proteins. Using estrogen-regulated c-myc and temperature-sensitive Raf-1 mutants, we found that Raf-1 activation could protect cells from c-myc-induced apoptosis. In conclusion, these results suggest (i) that Raf-1 participates in v-abl transformation via an Erk-independent pathway by providing a survival signal which complements c-myc in transformation, and (ii) that cAMP agonists might become useful for the treatment of malignancies where abl oncogenes are involved, such as chronic myeloid leukemias.

Deoxyribonuclease II purified from the isolated lysosomes of porcine spleen and from porcine liver homogenates. Comparison with deoxyribonuclease II purified from porcine spleen homogenates.

Porcine spleen DNase II (EC 3.1.22.1), one of the best-characterized DNases II, is subcellularly located in lysosomes because the enzyme is co-sedimented with two of the lysosomal marker enzymes, cathepsin D and acid phosphatase. The physicochemical properties, including the subunit structure, sensitivity to iodoacetate inactivation, native molecular weight and chromatographic behavior, of the DNase II purified from the isolated lysosomes of porcine spleen are indistinguishable from those of the same enzyme purified from the whole porcine spleen homogenate. DNase II can also be extracted from porcine liver with 0.05 M H2SO4 or 0.1 M NaCl and purified from either extract by a series of column chromatographies. The purified liver DNase II from either extract has the same subunit structure (alpha-chain, Mr 35,000 and beta-chain, Mr 10,000) as the purified DNase II of porcine spleen. The two liver extracts as well as the extracts of spleen and gastric mucosa contain DNase II with very similar properties on Sephadex G-100 gel filtration, on acid polyacrylamide gel electrophoresis under non-denaturing conditions, and on isoelectric focusing. The data strongly suggest that, for the same species of animal, the DNase II activities in various tissues are associated with protein molecules of identical structure.

Using biosensors to detect the release of serotonin from taste buds during taste stimulation.

CHO cells transfected with high-affinity 5HT receptors were used to detect and identify the release of serotonin from taste buds. Taste cells release 5HT when depolarized or when stimulated with bitter, sweet, or sour tastants. Sour- and depolarization-evoked release of 5HT from taste buds is triggered by Ca2+ influx from the extracellular fluid. In contrast, bitter- and sweet-evoked release of 5HT is triggered by Ca2+ derived from intracellular stores.

Migrating esophageal foreign bodies.

UNLABELLED: Ingested foreign bodies which migrate extraluminally, although rare in occurrence, are fraught with the potential to cause life-threatening complications. PURPOSE OF THE STUDY: To discuss the management of this pathology. MATERIAL AND METHODS: A series of four patients with such occurrences is presented. CONCLUSION: A discussion on the safe management of such seemingly innocuous foreign bodies allows the authors to propose a therapeutical algorythm.

Morphological changes induced by prostaglandin E in cultured rat osteoblasts.

Prostaglandin E (PGE)-induced morphological changes of osteoblasts and its possible mechanisms were investigated in cultured calvaria and isolated osteoblasts from long bone fragments of neonatal rats. The control osteoblasts, either on the calvaria or isolated from the long bone fragments, were flat, polygonal in shape, and arranged in a monolayer under scanning electron microscopy (SEM) or phase contrast microscopy. Treatment with 1 mumol/L of prostaglandin E2 (PGE2, 2 h) caused these bone cells to contract a soma, whereas 10 and 100 mumol/L PGE2 (2 h) caused 18%-30% of the bone cells to elongate and expose the undersurface. Incubation of the cultured osteoblasts with PGE2 at different time periods showed a bell-shaped pattern with the optimal response at 2 h of incubation. A similar reaction can be induced by treatment with prostaglandin E1 (PGE1) or dibutyryl cyclic adenosine monophosphate (DBcAMP) in combination with 3-isobutyl-1-methylxanthine (IBMX). Furthermore, we assessed the percentage of responsive isolated bone cells to investigate interactions with other agents. The morphological changes induced by PGEs were inhibited by H-8, a protein kinase inhibitor. On the other hand, elevated intracellular calcium enhanced the PGE-induced morphological changes. Fluorescence labeling showed that PGEs caused the breakdown of the actin microfilaments, but spared the microtubules and vimentin filaments in the isolated osteoblast-like cells. These results suggest that the morphological changes of osteoblasts induced by PGEs may be related to the intracellular cAMP and calcium levels.

Electron probe x-ray microanalysis of small granulated cells in rat sympathetic ganglia after sequential aldehyde and dichromate treatment.

Rat adrenal medulla and celiac-mesenteric sympathetic ganglia were fixed by a glutaraldehyde/formaldehyde-potassium dichromate-osmium treatment sequence and plastic-embedded. Fine sections were examined by electron probe x-ray microanalysis. Comparable peaks for chromium (Kalpha = 5.4 keV) were obtained from cytoplasmic fields containing membrane-bounded inclusion granules in both adrenomedullary noradrenaline cells and a type (type II) of sympathetic small granulated cell whose inclusion granules closely resemble those of the adrenomedullary noradrenaline cell. Chromium was not detected in granules within adrenomedullary adrenaline cells nor in two other sympathetic small granualted cell types. In no material was chromium detected in agranular cytoplasmic or nuclear fields. Since chromium binds to the Schiff monobase formed by glutaraldehyde and noradrenaline during fixation, we infer that noradrenaline is present in the granules of the type II sympathetic small granulated cell, as well as in adrenomedullary noradrenaline cells.

ZIO impregnation and cytochemical localization of thiamine pyrophosphatase and acid phosphatase activities in small granule-containing (SGC) cells of rat superior cervical ganglia.

Cytochemical relationship between Golgi complex and dense-cored granules (DCGs) of small granule-containing (SGC) cells in rat superior cervical ganglia was examined in electron microscopy by zinc-iodide-osmium tetroxide (ZIO) method and by enzyme cytochemistry for thiamine pyrophosphatase (TPPase) and acid phosphatase (ACPase). After ZIO impregnation, all the saccules of Golgi apparatus and some of tubular rough endoplasmic reticulum (rER) were stained. DCGs in periphery of SGC cells were not stained, but varying degrees of dense deposits occurred in the DCGs in vicinity of Golgi trans-saccules. Both TPPase and ACPase activities were localized in one or two stacked layers of saccules on the trans side of the Golgi complex. No reaction products were demonstrated in the DCGs. From these results, we suggest that the DCGs of SGC cells in rat superior cervical ganglia are derived from the Golgi complex, and that lysosomal cleavage of protein contents in the DCGs may occur in the trans Golgi saccules.

Chromaffinity, uranaffinity and argentaffinity of small granule-containing (SGC) cells in rat superior cervical ganglia.

A systemic examination on the small granule-containing (SGC) cells in rat superior cervical ganglia was conducted by conventional and cytochemical electron microscopy including chromaffin, argentaffin and uranaffin reactions. According to the fine structure of dense cored vesicles (DCVs) in the cytoplasm, three types of small granule-containing (SGC) cells were revealed--Type I: 90-160 nm vesicles with cores of moderate or low electron density; Type II: 130-330 nm vesicles, polymorphic with highly electron dense cores; Type III: elongated vesicles (170 nm x 60 nm) with cores of moderate to low electron density. The majority of SGC cells were the Type I cells (78%) and Type II and III cells made up 13% and 9% of SGC cell population, respectively. Cytochemical results demonstrated that only the Type II cells displayed a positive chromaffin reaction and all three types of SGC cells showed argentaffinity and uranaffinity. The present study is the first to demonstrate the argentaffin reaction at ultrastructural level in SGC cells of sympathetic ganglia. Based on the results of the present study we also concluded that (1) the DCVs of Type II SGC cells contained noradrenaline and (2) biogenic amines and nucleotides (ATPs) coexisted in the DCVs of all three types of SGC cells.

The permeability of capillaries among the small granule-containing cells in rat superior cervical ganglia: an ultrastructural lanthanum tracer study.

The permeability of blood capillaries associated with small granule-containing (SGC) cells in rat superior cervical ganglia was investigated at ultrastructural level by employing ionic lanthanum as an electron dense tracer. In rat superior cervical ganglia, the majority of blood capillaries were nonfenestrated. Both fenestrated and nonfenestrated capillaries were observed in the area associated with SGC cells. Lanthanum tracer was observed in the luminal surface, the interendothelial cleft and the subendothelial perivascular spaces of both fenestrated and nonfenestrated capillaries associated with SGC cells. The external lamina of the Schwann cell which surrounded the neurons, nerve fibres and SGC cells were clearly delineated by the lanthanum tracer. Furthermore, the perineuronal space, the periaxonal space, and the pericellular space of the SGC cells were readily accessible to the lanthanum ion. The results demonstrated an absence of blood-nerve barrier, blood-ganglionic and blood-SGC cell barrier to the lanthanum ion in the parenchymal area of the SGC cells in rat superior cervical ganglia. It is proposed that lanthanum may pass through the endothelial cells via 1) the fenestrae of fenestrated capillaries, 2) the intercellular junctions of both fenestrated and nonfenestrated capillaries, i.e., a paracellular pathway; and 3) the process of endocytosis/exocytosis, i.e., a transcellular pathway, to reach the subendothelial space and be distributed in the parenchyma of SGC cells in rat superior cervical ganglia.

Ultrastructural studies on myofibrillogenesis and neogenesis of skeletal muscles after prolonged traction in rabbits.

Little is known about the morphological response of muscle after long term traction. The purpose of this study was to investigate the morphological changes of skeletal muscle during limb lengthening. After application of mini-extraskeletal fixator, the hindlimb of New Zealand white rabbit was osteotomized and then slowly lengthened at the rate of 1 mm/day up to a 20 mm gain in length. The muscles of hindlimbs were perfused and dissected. Morphological studies were performed at electron microscopic level. Transmission electron microscopy revealed foci of microtrauma at the myotendinous junction. The distance between the muscle fibers and tendon parenchyma increased, with numerous primitive mesenchyme-like cells interposed within this gap. The cytoplasmic space of these cells was devoid of myofibril formation at the ends of stretched fibers. Within the satellite near the myotendinous junction myofilament production was observed in various gradations of maturation. It is concluded that myofibrillogenesis with traction neogenesis of skeletal muscle during limb lengthening does exist and occurs mainly near the myotendinous junction. The myotendinous junction in mature skeletal muscle actively participated in the process of limb lengthening.

Analysis of neogenesis in rabbit skeletal muscles after chronic traction.

After application of a modified Orthofix mini-extraskeletal fixator, the hind limb of New Zealand White rabbits was osteotomized and then slowly lengthened at a rate of 1 mm/day. After a 20 mm gain in length, the net weight and the length of muscular and tendinous portions were measured and histological examination was carried out in triceps surae muscles. Quantitative analysis showed a significant increase in the gained length of the muscular portion (28.05% to 30.65%). Histological studies of these lengthened muscles showed a generalized increase in cellularity with scanty inflammatory cell infiltration near the myotendinous junction. The increased cellularity is due to the presence of muscle precursor cells characterized by large, oval and pale-stained vesicular nuclei and two prominent nucleoli. The nuclei of these precursor cells were larger and more numerous near the myotendinous junction, and gradually changed into a flattened and more condensed form at a distance from the junction. Occasionally, chains of centrally-located nuclei of primitive myoblasts were also visible. It is concluded that traction neogenesis of the skeletal muscle during limb lengthening does exist and occurs mainly near the myotendinous junction.

Biochemical and histopathological changes in the mortality caused by acute ischemic limb injury: a rabbits' model.

Restoration of blood flow to an acute ischemic extremity may deteriorate the ischemic injury, lead to multiple organ dysfunction or even death. This paradox of continuing injury during reperfusion is not completely understood. The role of multi-organ damage in the mortality caused by ischemic limb injury is also still not clarified. The purpose of this study is to determine the biochemical and histopathological changes in the mortality caused by ischemic limb injury. After anesthesia, the hindlimbs of 14 New Zealand white rabbits were made ischemic and set into 8 hours or 12 hours of ischemia. Blood samples were obtained then the creatine kinase (CK) levels were determined and CK isoenzymes analyzed. All rabbits with 8 hours' ischemia survived well, and 5 of the 7 rabbits with 12 hours' ischemia expired within 8 hours after reperfusion. CK elevation was correlated most strongly with the time of the ischemic insults. The percentage of CK-MB isoenzyme remained unchanged after 8 hours' ischemia-reperfusion insult, while increased significantly after 12 hours' ischemia-reperfusion insult. Histologic examinations showed that the major systemic manifestation was massive destruction of the liver and kidney. The injuries are more obvious in areas with the greatest blood flow during reperfusion. We concluded that the ratio of CK-MB isoenzyme is most useful for distinguishing the risk of mortality caused by acute ischemic limb injury, and the cause of systemic complications are attributed to the multi-organ failure.

Electron microscopic immunocytochemistry of glutamate-containing nerve fibers in the taste bud of mudpuppy (Necturus maculosus).

The presence of glutamate immunoreactivity (glu-IR) in the nerve fibers of the mudpuppy taste bud was investigated by electron microscopy. Pre-embedding staining with avidin-biotin-peroxidase complex (ABC) and post-embedding staining with 5 nm colloid gold conjugates were used separately to identify immuno-stained structures. We have found the following: 1) the majority of the nerve fibers innervating the mudpuppy taste bud are unmyelinated; 2) about 85% of nerve fibers located at the base of the taste bud and about 60% of the nerve fibers located between the taste cells show glu-IR by pre-embedding staining; 3) there is a preferential staining of the glu-IR in the nerve fibers of the mudpuppy taste bud; and 4) the distribution of the colloidal gold particles in the nerve fibers is 1.5 to 2 times denser than that of the staining in the connective tissue background or cellular profiles of taste cells. From the distribution and pattern of the nerve fibers obtained in the thick and thin sections, we conclude that the mudpuppy taste bud is innervated by glutamate-containing unmyelinated nerve fibers.

Reserpine-induced catecholamine depletion from small cells in rat sympathetic ganglia.

Two reserpine dosage schedules were applied to Wistar rats (a) 5 mg/kg i.p. 6 hr before sacrifice and (b) 5 mg/kg i.p. at 36, 24 and 12 hr prior to sacrifice. Control animals were correspondingly sham-injected. The coeliac-mesenteric ganglion complex was removed and processed either for the Falck-Hillarp fluorescence histochemical technique or fixed in glutaraldehyde followed by 3.5% potassium dichromate for a chromaffin-type reaction. After a single reserpine injection there was a statistically significant (p less than 0.001) reduction in the percentage of 'chromaffin-positive' cells and a statistically significant (p less than 0.001) increase in the percentage of 'chromaffin-negative' cells compared with controls. No obvious reduction in fluorophore emission from small intensely fluorescent (SIF) cells was observed. After prolonged reserpinization (3 x 5 mg/kg) there was a highly significant reduction in the percentage of 'chromaffin-positive' small cells and also a significantly lower (by a factor of 2) level of fluorescent emission from SIF cells. The catecholamine-releasing potential of small cells is demonstrated by these results.

Age-related changes in locomotor behavior induced by MPTP in rats.

Effect of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on gait was studied in young (4 weeks) and old (21 months) male rats. No significant alteration in stride length (SL) or stride width (SW) was observed 30 min after single dose MPTP treatment (3 mg/kg, i.p.) in both young and old rats. Multidose treatment with MPTP (3 mg/kg, i.p. daily for 8 days) resulted in a marked decrease in SL in old rats compared to that of old control group, while an increase in SL was found in both MPTP-treated and control young rats. In contrast, multidose MPTP administration caused no changes in SW in either young or old rats. The present result of behavioral analysis suggests that multidose MPTP neurotoxic effect on locomotor activity may be age dependent in rats and that the old rat is an appropriate model for MPTP studies.

Differential permeability of blood microvasculatures in various sympathetic ganglia of rodents.

The ultrastructure of capillaries and their permeability to lanthanum ion and horseradish peroxidase (HRP) in various rodent sympathetic ganglia were investigated in this study. Electron microscopic observation revealed that most capillaries surrounding the principal neurons in these ganglia were of the continuous (non-fenestrated) type, while the fenestrated capillaries were consistently associated with the small granule-containing (SGC) cells in rat and hamster superior cervical ganglia and the coeliac-mesenteric ganglia (CMG) complex. Both of the capillaries surrounding the principal neurons and adjacent to SGC cells in various gerbil sympathetic ganglia or in rat and hamster thoracic ganglia were of the non-fenestrated type. After lanthanum perfusion, lanthanum tracer was limited to the blood-vessel lumen but was apparently obstructed by the tight junctions of capillaries. No lanthanum was visible in the extravascular space surrounding the principal neurons of rodent superior cervical and thoracic ganglia. By contrast, lanthanum extravasation was observed in the luminal, abluminal and perivascular surface of capillaries in the CMG complex and near SGC cells in the superior cervical ganglion. Injecting HRP showed that all blood vessels in various sympathetic ganglia were impermeable to HRP. HRP-DAB reaction product was limited to the lumen of capillaries, blocked by tight junctions and obstructed by fenestral diaphragms of fenestrated capillaries close to SGC cells. We conclude that: (1) the capillaries surrounding the principal neurons in rodent superior cervical and thoracic ganglia are more restrictive to HRP and lanthanum ion than those anywhere in the CMG complex or in regions containing SGC cells of superior cervical ganglia; (2) according to the results of lanthanum and HRP experiments, the existence of different blood-barrier properties are present among different rodent sympathetic ganglia or within the same ganglion.

TUNEL staining and electron microscopy studies of apoptotic changes in the guinea pig vallate taste cells after unilateral glossopharyngeal denervation.

On the basis of our previous report that unilateral glossopharyngeal neurectomy in the guinea pig resulted in degeneration and disappearance of taste buds in ipsilateral vallate papillae (Huang and Lu 1996), it is reasonable to speculate that gustatory denervation may enhance apoptosis of taste bud cells, with taste buds decreasing in number and ultimately disappearing after neurectomy. We were therefore determined to investigate apoptosis of taste bud cells in guinea pig vallate papillae after unilateral glossopharyngeal neurectomy using both terminal deoxynuleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) at the light microscopic level and by conventional electron microscopy. A total of 34 adult guinea pigs were unilaterally glossopharyngeal-neurectomized and sacrificed at 3, 6, 12 h and 1, 3 and 7 days after surgery. The results revealed that only a very few TUNEL-positive nuclei indicating apoptosis were present in normal taste buds, but in surgically denervated papillae, they increased in number from 6 h-12 h after surgery, reached at peak on day 1 and then gradually decreased. In apoptotic cells from normal taste buds, electron microscopy revealed condensation of the chromatin against the nuclear envelope, changes in the nuclear envelope, and fragmentation of the nucleus, but the integrity of the plasma membrane and organelles was maintained. Neurectomized taste cells were also characterized by condensed and fragmentary nuclei, compactness of the cytoplasmic organelles, and the appearance of pedunculated protuberances on the cell surface. From these observations, we conclude that: (1) glossopharyngeal neurectomy enhanced apoptosis of vallate taste bud cells in guinea pig; (2) appropriate gustatory nerve innervation is an essential component for the maintenance of the taste bud, and may play a role in apoptosis of taste cells.

The distribution of PGP9. 5, BDNF and NGF in the vallate papilla of adult and developing mice.

The development and innervation of vallate papillae and taste buds in mice were studied using antibodies against the neuronal marker, protein gene product 9.5 (PGP 9.5), and against nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). PGP 9.5 immunohistochemical studies revealed that the earliest sign of median vallate papilla formation was an epithelial bulge at embryonic day 13 (E13), and at E14, a dense nerve plexus was found within the connective tissue core of the papilla. Thin nerve fibers penetrated the apical and medial trench wall epithelium of the papilla at E16 and a few of these began to invade the lateral trench wall epithelium at E17. At postnatal day 1 (P1), the newly formed taste buds were recognizable and a small number of PGP 9.5-immunoreactive (IR) cells appeared on the medial trench wall epithelium. The number of PGP 9.5-IR taste bud cells then increased gradually and reached the adult level at postnatal week 2. PGP 9.5 immunoreactivity increased systematically with age. NGF and BDNF immunoreactivity was first seen at the boundary between the columnar cells in the apical epithelium of the developing vallate papilla at E13, then in the medial and lateral trench walls at E15 (BDNF) or E18 (NGF). At P1, BDNF immunoreactivity was exclusively present in the newly formed taste buds of the medial trench wall. The number of BDNF-IR taste bud cells then increased gradually, reaching the adult level at P7. Similar degrees of NGF and BDNF immunoreactivity were seen in the developing vallate papilla. In the present study, we found that the vallate papilla was formed prior to its innervation, and we propose that initiation of papilla formation does not require any direct influence from the specific gustatory nerve. We also suggest that neurotrophins in the early developing vallate papillae might act as local tropic factors for the embryonic growth of nerve fibers to induce differentiation of the taste buds.

[Ultrastructure changes of the remnant regenerating hepatocytes after partial hepatectomy in rats].

In spite of its highly functionally differentiated characteristics, the remnant liver has the capability of regeneration after massive hepatectomy either in human beings or in experimental animals. This experiment was performed to study the ultrastructural changes of the regenerated hepatocytes after massive hepatectomy. Male Wistar rats weighing around 200g were used in this study. Partial hepatectomy with resection of the median and left lateral lobes (67.31%) was performed. The rats were sacrificed at 6, 24, 48 and 72 hours after the operation. The remnant liver was inspected under a light and electron microscope. We found that: (1) the glycogen in the cytoplasm of hepatocyte nearly disappeared 6 hours after hepatectomy, with a decrease of rough endoplasmic reticulum (RER) and an increase of smooth endoplasmic reticulum (SER) and lysosomes were noted; (2) 24 hours after hepatectomy, (the nuclear membrane became zigzag shaped and the reappearance of glycogen and an increase of RER, autophagosome and lipid droplets were noted. (3) the number of mitosis increased markedly at 48 hours postoperatively; and (4) 72 hours after hepatectomy, the lysosome and RER returned to preoperative condition with some RER became dilated; SER was hardly found and lipid droplets became bigger and increased; and the nuclear membrane shape was still a zigzag at this time.

Effects of zinc deficiency on the vallate papillae and taste buds in rats.

BACKGROUND AND PURPOSE: Zinc deficiency is associated with multiple clinical complications, including taste disturbance, anorexia, growth retardation, skin changes, and hypogonadism. We investigated the zinc-deficiency-induced morphologic changes in the vallate taste buds of weanling and young adult male Wistar rats. METHODS: A total of 24 weanling and 30 young adult rats were used. Each age group was further divided into a control group fed a zinc-adequate (50 ppm) diet, a zinc-deficient (< 1 ppm) diet group, and a zinc-adequate pair-fed group who were fed the same amount of food as that taken by the zinc-deficient group. Weanling rats were fed for 4 weeks and young adult rats were fed for 6 weeks. The morphometry and morphologic changes of vallate taste buds were analyzed using light and transmission electron microscopy. RESULTS: Light microscopy revealed no significant difference in papilla size and morphology among the various groups. In both weanling and young adult rats in the zinc-deficient diet and pair-fed groups, the number of taste buds per papilla (per animal) and the average profile area of the taste bud were significantly smaller than those of the corresponding controls (p < 0.05). Ultrastructural changes were seen only in the taste buds of weanling rats fed the zinc-deficient diet, with derangement of the architecture of the taste bud and widening of the intercellular space between taste bud cells. The proportion of type I taste bud cells in the taste buds of weanling rats fed the zinc-deficient diet decreased from 59% to 39%, and that of type II taste bud cells decreased from 25% to 12%. No obvious changes in the ultrastructure of type III taste bud cells were observed. CONCLUSIONS: The main effects of zinc deficiency in weanling and young adult rats and in adequate diet pair-fed rats were changes in the number and size of taste buds, and fine structure changes in the taste bud cells, especially during the accelerated growth stage after weaning.