Mapping of cytoskeletal components in the hippocampal formation of the tree shrew (Tupaia belangeri)

The distribution of the major cytoskeletal components in frontal cryosections of the hippocampal formation of adult male tree shrews (Tupaia belangeri) was immunohistochemically investigated by using commercially available antibodies. Actin-immunolabeling was evident in all layers of the dentate gyrus as well as in the regio superior (CA1) and the regio inferior (CA3). Neurofilament 160 was detected only in the molecular layer of the dentate gyrus and in the axons of the granule cells (mossy fibers). For beta-tubulin, the microtubule associated proteins (MAPs) MAP2AB, MAP2ABC and Tau, immunoreactivity was evident within the granule cells and within the somatodendritic compartment of pyramidal neurons. Granule cells and the somata of the pyramidal neurons were intensely labeled for kinesin. Our findings show the elaborate expression of cytoskeletal proteins in the hippocampal formation of the tree shrew, relatively similar to what is seen in other species but with also some important differences, such as the immunonegativity of the axonal compartment for Tau in the tree shrew, which is contrary to what we see in the mouse (unpublished data). These findings provide useful insights regarding the organization of the hippocampal formation of the tree shrew and are fundamental for further research in this field.

Distinctive compartmental organization of human primary visual cortex

In the primary visual area of macaques and other monkeys, layer 4A is a mosaic of separate tissue compartments related to the parvocellular (P) and magnocellular (M) layers of the lateral geniculate nucleus. This mosaic resembles a honeycomb, with thin walls that receive direct P inputs and cores consisting of columns of dendrites and cell bodies ascending from layer 4B, a layer that receives indirect M inputs. To determine whether apes and humans have a macaque-like layer 4A, we examined the primary visual area in humans, chimpanzees, an orangutan, Old World monkeys, and New World monkeys. Apes and humans lacked the dense band of cytochrome oxidase staining in layer 4A that marks the stratum of P-geniculate afferents in monkeys. Furthermore, humans displayed a unique arrangement of presumed M-related cells and dendrites in layer 4A, as revealed with antibodies against nonphosphorylated neurofilaments and microtubule-associated protein 2. Human 4A contained a large amount of M-like tissue distributed in a complex, mesh-like pattern rather than in simple vertical arrays as in other anthropoid primates. Our results suggest that (i) the direct P-geniculate projection to layer 4A was reduced early in the evolution of the ape-human group, (ii) the M component of layer 4A was subsequently modified (and possibly enhanced) in the human lineage, and (iii) the honeycomb model does not adequately characterize human layer 4A. This is the first demonstration of a difference in the cortical architecture of humans and apes, the animals most closely related to humans.

The cyclin-dependent kinase inhibitor p27Kip1 is localized to the cytosol in Swiss/3T3 cells

p27Kip1 plays an important role in cell cycle progression by negatively regulating the activity of cyclin-Cdk complexes. To understand how p27Kip1 functions, the level and subcellular location of p27Kip1 in Swiss/3T3 cells following serum stimulation of quiescent cells was examined. Surprisingly, p27Kip1 was observed exclusively in the cytosol throughout G1 and into early S phase. However, as expected, p27Kip1 in the cytosolic fraction was greatly reduced following serum stimulation and reached very low levels by late G1. The decline in the level of p27Kip1 corresponded in time to an increase in the nuclear level of both Cdk2 and cyclin E. In quiescent 3T3 cells Cdk2 was inactive and co-precipitated with p27Kip1. After serum stimulation, both nuclear and cytosolic Cdk2 was activated and this corresponded to the decline in p27Kip1. Overexpression of p27Kip1 allowed accumulation of the inhibitor in the nucleus but inhibited entry of Cdk2 into the nucleus following serum stimulation. The subcellular localization of p27Kip1 was also examined in a variety of other mammalian cells. In all the cell lines examined the preponderance of p27Kip1 was found in the cytosolic fraction. However, a substantial level of nuclear p27Kip1 was observed for several cell lines. In a primary mixed glial cell culture p27Kip1 was localized to the nucleus. The results suggest that cytosolic p27Kip1 has a functional role in regulating cell cycle progression, possibly through inhibiting transport of cyclin E-Cdk 2 complexes into the nucleus.

Lamina-specific synaptic activation causes domain-specific alterations in dendritic immunostaining for MAP2 and CAM kinase II

Polyribosomal complexes are selectively localized beneath postsynaptic sites on neuronal dendrites; this localization suggests that the translation of the mRNAs that are present in dendrites may be regulated by synaptic activity. The present study tests this hypothesis by evaluating whether synaptic activation alters the immunostaining pattern for two proteins whose mRNAs are present in dendrites: the dendrite-specific cytoskeletal protein MAP2 and the alpha-subunit of CAMKII. High-frequency stimulation of the perforant path projections to the dentate gyrus, which terminate in a discrete band on the dendrites of dentate granule cells, produced a two-stage alteration in immunostaining for MAP2 in the dendritic laminae. Five minutes of stimulation (30 trains) caused a decrease in MAP2 immunostaining in the lamina in which the activated synapses terminate. After more prolonged periods of stimulation (1-2 hr), there was an increase in immunostaining in the sideband laminae just proximal and distal to the activated band of synapses. The same stimulation paradigm produced a modest increase in immunostaining for alpha-CAMKII in the activated laminae, with no detectable changes in the sideband laminae. The alterations in immunostaining for MAP2 were diminished, but not eliminated, by inhibiting protein synthesis; the increases in CAMKII were not. These findings reveal that patterned synaptic activity can produce domain-specific alterations in the molecular composition of dendrites; these alterations may be caused in part by local protein synthesis and in part by other mechanisms.

Reduced expression of p27(Kip1) protein in relation to salivary adenoid cystic carcinoma metastasis

BACKGROUND

Adenoid cystic carcinoma (ACC) is a malignant tumor of salivary gland origin. It tends to grow slowly but shows frequent recurrence and metastasis, ultimately with a poor outcome. Reduced expression of a cyclin-dependent kinase inhibitor, p27(Kip1), has been reported to correlate with poor survival for patients with various types of carcinoma. However, there has been no previous study reported of p27(Kip1) expression in ACC, to the authors' knowledge.

METHODS

To evaluate p27(Kip1) as a prognostic marker, the authors examined the immunohistochemical expression of p27(Kip1) protein in 29 ACCs and correlated its expression with clinicopathologic findings. Eleven pleomorphic adenomas (PAs) were also examined to compare the p27(Kip1) expression in benign and malignant salivary gland tumors.

RESULTS

All PAs expressed p27(Kip1) at high levels, whereas 83% of ACCs (24 of 29) showed reduced expression of this protein. Furthermore, the expression levels were significantly lower in ACCs with metastasis than in those without metastasis. The authors also examined the expression of p27(Kip1) in 2 ACC cell lines (ACCh and ACC3) by Northern and Western blot analysis to elucidate the possible mechanism of p27(Kip1) reduction in ACC. Both ACCh and ACC3 expressed p27(Kip1) mRNA, but ACCh did not produce p27(Kip1) protein. In ACCh, the expression of p27(Kip1) protein was induced by treatment with a proteasome inhibitor.

CONCLUSIONS

Overall, these findings suggest that reduced expression of p27(Kip1) may correlate with the development and progression of salivary ACC and can be an indicator of its malignant behavior. They also suggest that increased proteasome-mediated degradation may play an important role in this reduction of p27(Kip1) expression.

Purification and analysis of authentic CLIP-170 and recombinant fragments

We have purified authentic CLIP-170 (cytoplasmic linker protein of 170 kDa) and fragments comprising functional domains of the protein to characterize the structural basis of the function of CLIP-170. Analysis of authentic CLIP-170 and the recombinant fragments by electron microscopy after glycerol spraying/low angle rotary metal shadowing reveals CLIP-170 as a thin, 135-nm-long molecule with two kinks in its central rod domain, which are approximately equally spaced from the two ends of the protein. The central domain consisting of heptad repeats, which is alpha-helical in nature and forms a 2-stranded coiled-coil, mediates dimerization of CLIP-170. The rod domain harbors two kinks, each spaced approximately 37 nm from the corresponding end of the molecule, thus providing mechanical flexibility to the highly elongated molecule. The N-terminal domain of CLIP-170 binds to microtubules in vitro with a stoichiometry of one dimeric head domain per four tubulin heterodimers. Authentic CLIP-170 binds to microtubules with lower stoichiometry, indicating that the rod and tail domains affect microtubule binding of CLIP-170. These results document that CLIP-170 is a highly elongated polar molecule with the microtubule-binding domain and the organelle-interacting domains at opposite ends of the homodimer, thus providing a structural basis for the function of CLIP-170 as a microtubule-organelle linker protein.

Synaptic control of glycine and GABA(A) receptors and gephyrin expression in cultured motoneurons

We have evaluated the influence of the secretory phenotype of presynaptic boutons on the accumulation of postsynaptic glycine receptors (GlyRs), type A GABA receptors (GABA(A)Rs), and gephyrin clusters. The cellular distribution of these components was analyzed on motoneurons cultured either alone or with glycinergic and/or GABAergic neurons. In motoneurons cultured alone, we observed gephyrin clusters at nonsynaptic sites and in front of cholinergic boutons, whereas glycine and GABA(A) receptors formed nonsynaptic clusters. These receptors are functionally and pharmacologically similar to those found in cultures of all spinal neurons. Motoneurons receiving GABAergic innervation from dorsal root ganglia neurons displayed postsynaptic clusters of gephyrin and GABA(A)Rbeta but not of GlyRalpha/beta subunits. In motoneurons receiving glycinergic and GABAergic innervation from spinal interneurons, gephyrin, GlyRalpha/beta, and GABA(A)Rbeta formed mosaics at synaptic loci. These results indicate that (1) the transmitter phenotype of the presynaptic element determines the postsynaptic accumulation of specific receptors but not of gephyrin and (2) the postsynaptic accumulation of gephyrin alone cannot account for the formation of GlyR-rich microdomains.

Regulation of the hepatocyte cell cycle by type I collagen matrix: role of cyclin D1

Rat hepatocytes adherent to a rigid film of type I collagen will spread and enter S phase, while those attached to collagen gel or a dried collagen substrate remain round and quiescent. The current studies were initiated to determine the mechanism by which these different substrates differentially influence cell cycle progression. Cyclin D1 mRNA and protein expression and associated kinase activity was low on dried collagen relative to collagen film. In contrast, cyclin E and cdk2 protein levels were similar on the two substrates. Although cyclin E and cdk2 were present, cells on dried collagen lacked cdk2 kinase activity. p27 protein levels did not differ between dried collagen and film, but more p27 was associated with cdk2 in cells on dried collagen than those on collagen film. Cyclin D1 expression on collagen film was inhibited by cytochalasin D and exoenzyme C3, suggesting a role for the GTP-binding protein, Rho, in regulating cyclin D1 expression. Cyclin D1 over-expression induced hepatocytes into S phase in the absence of cell shape change on dried collagen or collagen gel. These results demonstrate a novel, substrate-dependent mechanism for cyclin D1 expression in hepatocytes, and also demonstrate that cyclin D1 over-expression allows shape-independent S phase entry.

A novel role for the cyclin-dependent kinase inhibitor p27(Kip1) in angiotensin II-stimulated vascular smooth muscle cell hypertrophy

Angiotensin II (Ang II) has been shown to stimulate either hypertrophy or hyperplasia. We postulated that the differential response of vascular smooth muscle cells (VSMCs) to Ang II is mediated by the cyclin-dependent kinase (Cdk) inhibitor p27(Kip1), which is abundant in quiescent cells and drops after serum stimulation. Ang II treatment (100 nM) of quiescent VSMCs led to upregulation of the cell-cycle regulatory proteins cyclin D1, Cdk2, proliferating cell nuclear antigen, and Cdk1. p27(Kip1) levels, however, remained high, and the activation of the G1-phase Cdk2 was inhibited as the cells underwent hypertrophy. Overexpression of p27(Kip1) cDNA inhibited serum-stimulated [(3)H]thymidine incorporation compared with control-transfected cells. This cell-cycle inhibition was associated with cellular hypertrophy, as reflected by an increase in the [(3)H]leucine/[(3)H]thymidine incorporation ratio and by an increase in forward-angle light scatter during flow cytometry at 48 hours after transfection. The role of p27(Kip1) in modulating the hypertrophic response of VSMCs to Ang II was further tested by antisense oligodeoxynucleotide (ODN) inhibition of p27(Kip1) expression. Ang II stimulated an increase in [(3)H]thymidine incorporation and the percentage of S-phase cells in antisense ODN-transfected cells but not in control ODN-transfected cells. We conclude that p27(Kip1) plays a role in mediating VSMC hypertrophy. Ang II stimulation of quiescent cells in which p27(Kip1) levels are high results in hypertrophy but promotes hyperplasia when levels of p27(Kip1) are low, as in the presence of other growth factors.

Sequence of neurodegeneration and accumulation of phosphorylated tau in cultured neurons after okadaic acid treatment

Within neurofibrillary tangles and dystrophic neurites of Alzheimer's disease (AD), the cytoskeletal protein tau is abnormally hyperphosphorylated. In the present study, we examined the effect of okadaic acid (OA), a protein phosphatase inhibitor, in rat cultured neurons. Low concentrations of OA induce degeneration of neurites, rounding of cell bodies, detachment from the substratum, and eventual neuronal death. During OA-induced degeneration, SMI-31 immunoreactivity became punctate in neurites at 6 h after OA treatment, and over time, accumulated in cell bodies and dystrophic neurites. Hyperphosphorylation of tau and marked loss of MAP-2-positive dendrites occurred after 6 h of treatment with OA. Thereafter, AT-8 and PHF-1 immunoreactivity accumulated in cell bodies and subsequently appeared in distal axon-like neurites. These results demonstrate that OA treatment induced hyperphosphorylation of tau and preferential dendritic damage, with subsequent accumulation of phosphorylated tau in cell bodies and dystrophic axon-like neurites. OA-induced neurodegeneration may provide a useful model to study AD.

SV40 small T antigen enhances progression to >G2 during lytic infection

The infection of monkey kidney (CV-1) cells with simian virus 40 (SV40) stimulates the cells into successive rounds of DNA synthesis without an intervening mitosis, leading to the acquisition of a >G2 DNA content. To elucidate the role of small t antigen in cell cycle progression and in viral replication during infection, studies were performed using an SV40 mutant (dl888) that lacks the ability to produce small t. Initially dl888-infected cells move through the first S phase at roughly the same rate as wild-type infected cells. Upon reaching G2, however, the dl888-infected cells progressed to >G2 at a reduced rate relative to wild-type. The slower rate of entry into >G2 of dl888-infected cells is associated with a decrease in total pRb and an increase in the ratio of hypophosphorylated to hyperphosphorylated pRb. The expression of cyclin D1 and p27(kip1) were elevated in dl888-infected cells compared to wild-type-infected CV-1 cells. Taken together, these results indicate that small t antigen plays a role in stimulating entry into >G2 in SV40-infected CV-1 cells, possibly by affecting the regulation of key cell cycle proteins.

Two compartments for insulin-stimulated exocytosis in 3T3-L1 adipocytes defined by endogenous ACRP30 and GLUT4

Insulin stimulates adipose cells both to secrete proteins and to translocate the GLUT4 glucose transporter from an intracellular compartment to the plasma membrane. We demonstrate that whereas insulin stimulation of 3T3-L1 adipocytes has no effect on secretion of the alpha3 chain of type VI collagen, secretion of the protein hormone adipocyte complement related protein of 30 kD (ACRP30) is markedly enhanced. Like GLUT4, regulated exocytosis of ACRP30 appears to require phosphatidylinositol-3-kinase activity, since insulin-stimulated ACRP30 secretion is blocked by pharmacologic inhibitors of this enzyme. Thus, 3T3-L1 adipocytes possess a regulated secretory compartment containing ACRP30. Whether GLUT4 recycles to such a compartment has been controversial. We present deconvolution immunofluorescence microscopy data demonstrating that the subcellular distributions of ACRP30 and GLUT4 are distinct and nonoverlapping; in contrast, those of GLUT4 and the transferrin receptor overlap. Together with supporting evidence that GLUT4 does not recycle to a secretory compartment via the trans-Golgi network, we conclude that there are at least two compartments that undergo insulin-stimulated exocytosis in 3T3-L1 adipocytes: one for ACRP30 secretion and one for GLUT4 translocation.

Prenatal exposure to aluminum reduces expression of neuronal nitric oxide synthase and of soluble guanylate cyclase and impairs glutamatergic neurotransmission in rat cerebellum

Exposure to aluminum (Al) produces neurotoxic effects in humans. However, the molecular mechanism of Al neurotoxicity remains unknown. Al interferes with glutamatergic neurotransmission and impairs the neuronal glutamate-nitric oxide-cyclic GMP (cGMP) pathway, especially in rats prenatally exposed to Al. The aim of this work was to assess whether Al interferes with processes associated with activation of NMDA receptors and to study the molecular basis for the Al-induced impairment of the glutamate-nitric oxide-cGMP pathway. We used primary cultures of cerebellar neurons prepared from control rats or from rats prenatally exposed to Al. Prenatal exposure to Al prevented glutamate-induced proteolysis of the microtubule-associated protein-2, disaggregation of microtubules, and neuronal death, indicating an impairment of NMDA receptor-associated signal transduction pathways. Prenatal exposure to Al reduced significantly the content of nitric oxide synthase and guanylate cyclase and increased the content of calmodulin both in cultured neurons and in the whole cerebellum. This effect was selective for proteins of the glutamate-nitric oxide-cGMP pathway as the content of mitogen-activated protein kinase and the synthesis of most proteins were not affected by prenatal exposure to Al. The alterations in the expression of proteins of the glutamate-nitric oxide-cGMP pathway could be responsible for some of the neurotoxic effects of Al.

Microtubule alterations in cultured taiep rat oligodendrocytes lead to deficits in myelin membrane formation

The taiep rat is a myelin mutant in which hypomyelination and progressive demyelination of the CNS are accompanied by an accumulation of microtubules within oligodendrocytes. To investigate whether and how the myelin defects were caused by microtubule abnormalities, we have established a taiep oligodendrocyte culture system in which mutant cells produce abnormally high levels of tubulin and microtubule-associated proteins and exhibit myelin defects. The studies show that abnormal microtubule accumulation and tight microtubule bundles developed in the taiep oligodendrocytes, with a higher ratio of minus-end-distal to plus-end-distal microtubules in their processes. Initially, in culture, immature taiep oligodendrocytes which have higher levels of tubulin than controls extend roughly twice as much membrane sheet as controls. The membrane sheets of the mature taiep oligodendrocytes which display the microtubule accumulation, however, grew much less rapidly compared to controls. By the fifth day in culture, a majority of the taiep oligodendrocytes had ceased the expansion of their membrane sheets and in some cases the sheets retracted. The levels of the myelin proteins, proteolipid protein and myelin-associated glycoprotein, were also markedly diminished in the mature taiep oligodendrocytes. Treatment with the microtubule depolymerizing drug nocodazole prevented not only the accumulation of microtubules but also restored the normal distribution of proteolipid proteins within the taiep oligodendrocytes. These data demonstrate that myelin synthesis in the oligodendrocyte cultures relies on the formation of a normal microtubule array, and the microtubule abnormalities are directly responsible for the myelin deficit in the taiep oligodendrocytes.

The neuroprotective effects of intrathecal administration of the selective N-type calcium channel blocker ziconotide in a rat model of spinal ischemia

PURPOSE

Spinal cord ischemia and resulting paraplegia represent a major complication associated with surgical repair of the thoracoabdominal aorta. Although the mechanism of spinal neuronal degeneration during ischemia is unclear, it may involve excessive calcium influx via N-type voltage-sensitive calcium channels (VSCCs). The neuroprotective capacity of intrathecal (IT) administration of the selective N-type VSCC blocker ziconotide, previously shown to be potently analgesic, was studied.

METHODS

In a rat aortic occlusion model, spinal cord ischemia was induced for 8, 9, or 10 minutes by occluding the descending thoracic aorta. Ziconotide was administered IT as (1) a continuous infusion of 300 or 600 ng/kg/h initiated 24 hours before ischemia and continuing an additional 24 hours or (2) a 0.3 microgram bolus injected 45 minutes before the induction of ischemia. Animals were allowed to live for 24 hours, and recovery of motor function was evaluated during this period. Spinal cords were processed using a silver impregnation technique and microtubule-associated protein type II (MAP2) immunohistochemistry.

RESULTS

Continuous IT infusion of ziconotide provided significant protection against 8- and 9-minute occlusions, but not 10-minute occlusions, as indicated by recovery of motor function, degree of spinal neuronal degeneration, and loss of MAP2 immunoreactivity. Acute IT pretreatment with ziconotide provided transient protection during the initial 4 hours of reperfusion; however, this protective effect was no longer present at 24 hours.

CONCLUSION

These data implicate N-type VSCC activation in spinal neuronal degeneration caused by transient spinal ischemia, because selective blockade of this channel by continuous IT infusion of ziconotide was protective against injurious intervals of spinal ischemia. Based on these findings, ziconotide may provide both neuroprotection and preemptive analgesia for aortic aneurysm surgery.

[Correlation between clinical aggressiveness of thymic epithelial tumors and expression of tumor suppressor gene products (p53, p27)]

It is impossible to predict malignant potential of thymomas by conventional histopathological examination. In order to find a malignant marker of thymoma, we immunohistochemically examined the expression of the products of p53 and p27kip1, potential tumor suppressor genes in thymic epithelial tumors. The thymic epithelial tumors examined in the present study included 13 non-invasive thymomas, 7 invasive thymomas, and 4 thymic carcinomas. The thymic epithelial cells showed abnormal accumulation of p53 protein in 2 of 13 non-invasive thymomas (15.4%), 4 of 7 invasive thymomas (50%), and 3 of 4 thymic carcinomas (75%). The frequency of p53-expression paralleled with clinical aggressiveness. On the other hand, p27 showed no correlation with clinical aggressiveness. In conclusion, the present results suggest that the presence of p53-positive epithelial cells might be a useful indicator to predict malignant potential of thymoma.

A cell cycle alteration precedes apoptosis of granule cell precursors in the weaver mouse cerebellum

A missense mutation in the gene coding for the G-protein-activated inwardly rectifying potassium (GIRK) channel, GIRK2, is responsible for apoptosis in the external germinal layer (EGL) of the cerebellum and a nonapoptotic death of midbrain dopaminergic neurons in the weaver (wv) mouse. Failure of axonogenesis and migration are considered to be the primary consequences of GIRK2 channel malfunction in the cerebellum. We investigated whether a disruption of the cell cycle precedes the failure of migration and axonogenesis and leads to massive apoptosis. To this end, immunohistochemistry and immunoblotting for PCNA, Cdk4, cyclin D, cyclin A, and the Cdk inhibitor p27/kip1, as well as in situ end-labeling for apoptotic DNA fragmentation, were applied to cerebella of P7-P21+/+, wv/+, and wv/wv mice. In +/+ and wv/+ mice, the expression of cell cycle proteins was limited to the outer, premigratory zone of the EGL. Antibodies to p27, a marker of cell differentiation, gave a reverse staining pattern. Due to migration delay, patches of p27-positive cells persisted in the outer EGL in P21 wv/+ mice. On the contrary, marked cell cycle up-regulation and absence of p27 occurred throughout the EGL at all ages in wv/wv mice, indicating an inability to switch off the cell cycle. Mitotic index evaluation showed that cell cycle activation was unrelated to proliferative events. Cell cycle proteins were not expressed in the substantia nigra, suggesting that nonapoptotic death of mature dopaminergic neurons is not preceded by abortive cell cycle re-entry. Our data show that abnormalities of the cell cycle in wv/wv cerebellum represent a major and early consequence of GIRK2 channel malfunction and may strongly influence the susceptibility of EGL cells to apoptosis. These observations may help in understanding the pathogenesis of human neurological channelopathies.

Platelet-activating factor (PAF) acetylhydrolase activity, LIS1 expression, and seizures

Lissencephaly patients are born with severe brain malformations and suffer from recurrent seizures. LIS1, the gene mutated in isolated lissencephaly patients, is a subunit of the heterotrimeric cytosolic enzyme platelet-activating factor acetylhydrolase (PAF-AH), interacts with tubulin, and affects microtubule dynamics. In order to gain molecular insights into the possible involvement of LIS1 in seizures in lissencephaly patients, we induced seizures in rats by injection of kainate. PAF-AH activity was markedly reduced as early as 30 min following initiation of seizures, making this parameter a sensitive indicator of seizure events. PAF-AH activity returned to and surpassed control values 1 week following initiation of seizures. Expression of LIS1 in the dentate gyrus changed significantly in a manner similar to that of PAF-AH enzymatic activity. This is the first correlation found between LIS1 expression and PAF-AH activity. Furthermore, the expression of the alpha2 catalytic subunit, which is the major PAF-AH catalytic subunit in rat adult brain, changed in a dramatic fashion. An additional higher-mobility LIS1 cross-reactive band was detected in samples isolated a week following seizure occurrence. This LIS1 isoform was enriched in the microtubule-associated fraction. We propose that LIS1 expression is an important factor in regulation of PAF-AH activity. We postulate that reductions in LIS1 protein levels found in lissencephaly patients may render them more susceptible to seizures.

Stimulation of neonatal and adult brain neurogenesis by subcutaneous injection of basic fibroblast growth factor

Mounting evidence indicates that extracellular factors exert proliferative effects on neurogenetic precursors in vivo. Recently we found that systemic levels of basic fibroblast growth factor (bFGF) regulate neurogenesis in the brain of newborn rats, with factors apparently crossing the blood-brain barrier (BBB) to stimulate mitosis. To determine whether peripheral bFGF affects proliferation during adulthood, we focused on regions in which neurogenesis persists into maturity, the hippocampus and the forebrain subventricular zone (SVZ). In postnatal day 1 (P1) rats, 8 hr after subcutaneous injection (5 ng/gm body weight), bFGF increased [(3)H]thymidine incorporation 70% in hippocampal and SVZ homogenates and elicited twofold increases in mitotic nuclei in the dentate gyrus and the dorsolateral SVZ, detected by bromodeoxyuridine immunohistochemistry. Because approximately 25% of proliferating hippocampal cells stimulated in vivo expressed neuronal traits in culture, bFGF-induced mitosis may reflect increased neurogenesis. bFGF effects were not restricted to the perinatal period; hippocampal DNA synthesis was stimulated by peripheral factor in older animals (P7-P21), indicating the persistence of bFGF-responsive cells and activity of peripheral bFGF into late development. To begin defining underlying mechanisms, pharmacokinetic studies were performed in P28 rats; bFGF transferred from plasma to CSF rapidly, levels rising in both compartments in parallel, indicating that peripheral factor crosses the BBB during maturity. Consequently, we tested bFGF in adults; peripheral bFGF increased the number of mitotic nuclei threefold in the SVZ and olfactory tract, regions exhibiting persistent neurogenesis. Our observations suggest that bFGF regulates ongoing neurogenesis via a unique, endocrine-like pathway, potentially coordinating neuron number and body growth, and potentially providing new approaches for treating damaged brain during development and adulthood.

Role of polysialic acid on outgrowth of rat olfactory receptor neurons

Towards elucidating the role of polysialic acid (PSA) in developing olfactory neuron of the rat, we injected neuraminidase (endo-N) into the olfactory nerve pathway under whole embryo culture, then employed immunohistochemistry to (i) detect expression of highly sialylated neural cell adhesion molecules (NCAM-H) and (ii) identify olfactory neurons via anti-microtubule-associated protein 1B (MAP1B) antibody. Olfactory axonal outgrowth from basal lamina occurred at the 31-somite stage and reached the olfactory bulb primordium at the 42-somite stage, being coincident with the timing and expression of NCAM-H immunoreactivity. Enzymatic removal of PSA by endo-N remarkably affected developmental processes of axonal outgrowth, extension, and pathfinding, i.e. individual axons appeared to have become stuck in the mesenchyme. Results indicate that PSA is critically involved with anti-adhesion cues associated with individual axonal growth during olfactory system development.

Expression and prognostic roles of the G1-S modulators in hepatocellular carcinoma: p27 independently predicts the recurrence

Expression of cell-cycle modulators at the G1-S boundary, retinoblastoma gene product (pRb), p21, p16, p27, p53, cyclin D1, and cyclin E was investigated with 104 hepatocellular carcinomas (HCC), as well as 90 of their adjacent noncancerous lesions and 9 normal liver control specimens. The labeling indices (LI) of pRb, p21, p16, and p27 were higher in HCC lesions than in the adjacent noncancerous lesions and normal controls. Especially, p27 LI in noncancerous lesions was significantly higher than that in normal livers (P =.011). Aberrant p53 expression and cyclin D1 and E overexpression were observed exclusively in HCC lesions. pRb was positive in 85.6% of the HCC cases and was not related to any clinicopathological parameters. The p21 LI was generally low (average, 5.5 +/- 9.8). Although a negative regulator, p21 LI was higher in cases with intrahepatic metastasis (P =.0359). The p16 LI was significantly decreased (P =.0121) in cases with advanced stage. p27 LI was significantly decreased in cases with portal invasion (P =.0409), poor differentiation (P <.0001), larger size (P =.0421), and intrahepatic metastasis (P =.0878, borderline significance). On the other hand, aberrant p53 expression showed positive relationships with poor differentiation (P =.0004) and Ki-67 LI (P =. 0047). Cyclin D1 overexpression was found in 32.6% of the cases and occurred more frequently in those with high Ki-67 LI (P =.0032), pRb expression (P =.0202), poor differentiation (P =.0612, borderline significance), and intrahepatic metastasis (P =.0675, borderline significance). Cyclin E was overexpressed in 35.5% and had positive relationships with Ki-67 LI (P =.0269) and stage (P =.0125). In univariate analysis, cases with p27 LI < 50 (P =.0004), cyclin D1 overexpression (P =.0041), and cyclin E overexpression (P =.0572, borderline significance) showed poorer outcomes for disease-free survival (DFS). In multivariate analysis, p27 expression could be recognized as an independent prognostic marker for DFS. These findings suggest that in HCC: 1) p27 is active against HCC progression in early phases and, possibly, hepatocarcinogenesis as a negative regulator and can be a novel prognostic marker for DFS; and 2) cyclin D1 predominantly works for cell-cycle progression at the G1-S boundary.

p27KIP1 is abnormally expressed in Diffuse Large B-cell Lymphomas and is associated with an adverse clinical outcome

Cell cycle progression is regulated by the combined action of cyclins, cyclin-dependent kinases (CDKs), and CDK-inhibitors (CDKi), which are negative cell cycle regulators. p27KIP1 is a CDKi key in cell cycle regulation, whose degradation is required for G1/S transition. In spite of the absence of p27KIP1 expression in proliferating lymphocytes, some aggressive B-cell lymphomas have been reported to show an anomalous p27KIP1 staining. We analysed p27KIP1 expression in a series of Diffuse Large B-cell Lymphoma (DLBCL), correlating it with the proliferative index and clinical outcome, to characterize the implications of this anomalous staining in lymphomagenesis in greater depth. For the above mentioned purposes, an immunohistochemical technique in paraffin-embedded tissues was employed, using commercially available antibodies, in a series of 133 patients with known clinical outcomes. Statistical analysis was performed in order to ascertain which clinical and molecular variables may influence outcome, in terms of disease-free survival (DFS) and overall survival (OS). The relationships between p27KIP1 and MIB-1 (Ki-67) were also tested. An abnormally high expression of p27KIP1 was found in lymphomas of this type. The overall correlation between p27KIP1 and MIB-1 showed there to be no significant relationship between these two parameters, this differing from observations in reactive lymphoid and other tissues. Analysis of the clinical relevance of these findings showed that a high level of p27KIP1 expression in this type of tumour is an adverse prognostic marker, in both univariate and multivariate analysis. These results show that there is abnormal p27KIP1 expression in DLBCL, with adverse clinical significance, suggesting that this anomalous p27KIP1 protein may be rendered non-functional through interaction with other cell cycle regulator proteins.

Loss of P27Kip1 expression correlates with tumor grade and with reduced disease-free survival in primary superficial bladder cancers

p27Kip1 is a member of the Cip1/Kip1 family of cyclin-dependent kinase inhibitors and is a potential tumor suppressor gene. We previously reported a deregulated expression of p27Kip1 in a series of human cancer cell lines and in primary breast and colon cancers. Moreover, p27Kip1 has been reported as an important prognostic factor in primary lung, breast, colon, and prostate cancers. In this study, we evaluated the prognostic value of p27Kip1 in a series of 96 superficial (pTa-1) human bladder carcinomas. High (>50% positive cells), moderate (25-50%), and low (<25%) p27Kip1 staining was observed in 39 (41%), 19 (20%), and 38 (39%) of the 96 primary superficial bladder cancers, respectively. No significant association was found between the expression level of p27Kip1 and tumor stage. Decreased p27Kip1 staining correlated with higher tumor grade (P = 0.001). Interestingly, a significant association was observed between increased expression of p27Kip1 and positivity for p53 (>20% positive cells; P < 0.001). A significant correlation was also observed between low expression of p27Kip1 and decreased disease-free survival (P = 0.0003 by log-rank test) and overall survival (P = 0.01 by log-rank test). Furthermore, on multivariate analysis, low p27Kip1 protein expression was an independent predictor of reduced disease-free survival (P = 0.018; relative risk = 1.95) second only to tumor stage. These data indicate that p27Kip1 protein is frequently expressed at low level in poorly differentiated tumors and suggest that this protein might represent a useful prognostic marker for disease recurrence and overall survival in superficial bladder carcinomas.

Expression of p27 is associated with Bax expression and spontaneous apoptosis in oral and oropharyngeal carcinoma

p27Kip1, a cyclin-dependent kinase inhibitor, is a negative regulator of the cell cycle, and apoptosis is a genetically encoded program of cell death. To clarify the relationship between the cell cycle and apoptosis, we investigated expression of p27, cyclin D1 and apoptosis-related proteins (p53, Bax, Bcl-2 and c-Myc) in 60 cases of oral and oropharyngeal squamous-cell carcinoma (SCC) using an immuno-histochemical approach, and evaluated spontaneous apoptosis in vivo. Our most notable finding was that spontaneous apoptosis in the p27-positive group was significantly higher than that in the p27-negative group (p = 0.028). In addition, the percentage of p27-positive cells was clearly correlated with that of Bax-positive cells (gamma = 0.288, p = 0.028) and with that of cyclin D1-positive cells (gamma = 0.416, p = 0.002). Expression of p27 was inversely associated with the clinical stage of total tumor progression (p = 0.027). However, no correlation was found between p27 expression and the following parameters: gender, tumor size, lymph node metastasis, overall survival and disease-free survival. Our results give evidence that the action of the cell-cycle regulator p27 is closely linked with apoptosis in clinical samples from patients and indicate that over-expression of p27 might induce apoptosis in cancer cells through elevation of Bax expression, thereby acting on tumor progression.

Expression of p21(Cip1/Waf1/Sdi1) and p27(Kip1) cyclin-dependent kinase inhibitors during human hematopoiesis

Expression of p21 and p27 cyclin-dependent kinase inhibitors is associated with induced differentiation and cell-cycle arrest in some hematopoietic cell lines. However, it is not clear how these inhibitors are expressed during normal hematopoiesis. We examined various human hematopoietic colonies derived from cord blood CD34(+) cells, bone marrow, and peripheral blood cells using a quantitative reverse transcription-polymerase chain reaction assay, immunochemistry, and/or Western blot analysis. p21 mRNA was expressed increasingly over time in all of the colonies examined (granulocytes, macrophages, megakaryocytes, and erythroblasts), whereas p27 mRNA levels remained low, except for erythroid bursts. Erythroid bursts expressed both p21 and p27 mRNAs with differentiation but expressed neither protein, whereas both proteins were expressed in megakaryocytes and peripheral blood monocytes. In bone marrow, p21 was immunostained almost exclusively in a subset of megakaryocytes and p27 protein was present in megakaryocytes, plasma cells, and endothelial cells. In megakaryocytes, reciprocal expression of p27 to Ki-67 was evident and an inverse relationship between p21 and Ki-67 positivities was also present, albeit less obvious. These observations suggest that a complex lineage-specific regulation is involved in p21 and p27 expression and that these inhibitors are involved in cell-cycle exit in megakaryocytes.