Heterogeneity in the molecular composition of excitatory postsynaptic sites during development of hippocampal neurons in culture

To determine their roles in the assembly of glutamatergic postsynaptic sites, we studied the distributions of NMDA- and AMPA-type glutamate receptors; the NMDA receptor-interacting proteins alpha-actinin-2, PSD-95, and chapsyn; and the PSD-95-associated protein GKAP during the development of hippocampal neurons in culture. NMDA receptors first formed nonsynaptic proximal dendrite shaft clusters within 2-5 d. AMPA receptors were diffuse at this stage and began to cluster on spines at 9-10 d. NMDA receptor clusters remained partially nonsynaptic and mainly distinct from AMPA receptor clusters until after 3 weeks in culture, when the two began to colocalize at spiny synaptic sites. Thus, the localization of NMDA and AMPA receptors must be regulated by different mechanisms. alpha-Actinin-2 colocalized with the NMDA receptor only at spiny synaptic clusters, but not at shaft nonsynaptic or synaptic clusters, suggesting a modulatory role in the anchoring of NMDA receptor at spines. PSD-95, chapsyn, and GKAP were present at some, but not all, nonsynaptic NMDA receptor clusters during the first 2 weeks, indicating that none is essential for NMDA receptor cluster formation. When NMDA receptor clusters became synaptic, PSD-95 and GKAP were always present, consistent with an essential function in synaptic localization of NMDA receptors. Furthermore, PSD-95 and GKAP clustered opposite presynaptic terminals several days before either NMDA or AMPA receptors clustered at these presumptive postsynaptic sites. These results suggest that synapse development proceeds by formation of a postsynaptic scaffold containing PSD-95 and GKAP in concert with presynaptic vesicle clustering, followed by regulated attachment of glutamate receptor subtypes to this scaffold.

Differential regional expression and ultrastructural localization of alpha-actinin-2, a putative NMDA receptor-anchoring protein, in rat brain

Fast chemical neurotransmission is dependent on ionotropic receptors that are concentrated and immobilized at specific postsynaptic sites. The mechanisms of receptor clustering and anchoring in neuronal synapses are poorly understood but presumably involve molecular linkage of membrane receptor proteins to the postsynaptic cytoskeleton. Recently the actin-binding protein alpha-actinin-2 was shown to bind directly to the NMDA receptor subunits NR1 and NR2B (), suggesting that alpha-actinin-2 may function to attach NMDA receptors to the actin cytoskeleton. Here we show that alpha-actinin-2 is localized specifically in glutamatergic synapses in cultured hippocampal neurons. By immunogold electron microscopy, alpha-actinin-2 is concentrated over the postsynaptic density (PSD) of numerous asymmetric synapses where it colocalizes with NR1 immunoreactivity. Thus alpha-actinin-2 is appropriately positioned at the ultrastructural level to function as a postsynaptic-anchoring protein for NMDA receptors. alpha-Actinin-2 is not, however, exclusively found at the PSD; immunogold labeling was also associated with filaments and the spine apparatus of dendritic spines and with microtubules in dendritic shafts. alpha-Actinin-2 showed marked differential regional expression in rat brain. For instance, the protein is expressed at much higher levels in dentate gyrus than in area CA1 of the hippocampus. This differential regional expression implies that glutamatergic synapses in various parts of the brain differ with respect to their alpha-actinin-2 content and thus, potentially, the extent of possible interaction between alpha-actinin-2 and the NMDA receptor.

The ability of human Schwann cell grafts to promote regeneration in the transected nude rat spinal cord

Advances in the purification and expansion of Schwann cells (SCs) from adult human peripheral nerve, together with biomaterials development, have made the construction of unique grafts with defined properties possible. We have utilized PAN/PVC guidance channels to form solid human SC grafts which can be transplanted either with or without the channel. We studied the ability of grafts placed with and without channels to support regeneration and to influence functional recovery; characteristics of the graft and host/graft interface were also compared. The T9-T10 spinal cord of nude rats was resected and a graft was placed across the gap; methylprednisolone was delivered acutely to decrease secondary injury. Channels minimized the immigration of connective tissue into grafts but contributed to some necrotic tissue loss, especially in the distal spinal cord. Grafts without channels contained more myelinated axons (x = 2129 +/- 785) vs (x = 1442 +/- 514) and were larger in cross-sectional area ( x = 1.53 +/- 0.24 mm2) vs (x = 0.95 +/- 0.86 mm2). The interfaces formed between the host spinal cord and the grafts placed without channels were highly interdigitated and resembled CNS-PNS transition zones; chondroitin sulfate proteoglycans was deposited there. Whereas several neuronal populations including propriospinal, sensory, motoneuronal, and brainstem neurons regenerated into human SC grafts, only propriospinal and sensory neurons were observed to reenter the host spinal cord. Using combinations of anterograde and retrograde tracers, we observed regeneration of propriospinal neurons up to 2.6 mm beyond grafts. We estimate that 1% of the fibers that enter grafts reenter the host spinal cord by 45 days after grafting. Following retrograde tracing from the distal spinal cord, more labeled neurons were unexpectedly found in the region of the dextran amine anterograde tracer injection site where a marked inflammatory reaction had occurred. Animals with bridging grafts obtained modestly higher scores during open field [(x = 8.2 +/- 0.35) vs (x = 6.8 +/- 0.42), P = 0.02] and inclined plane testing (x = 38.6 +/- 0. 542) vs (x = 36.3 +/- 0.53), P = 0.006] than animals with similar grafts in distally capped channels. In summary, this study showed that in the nude rat given methylprednisolone in combination with human SC grafts, some regenerative growth occurred beyond the graft and a modest improvement in function was observed.

Down-regulation of IL-4 gene transcription and control of Th2 cell differentiation by a mechanism involving NFAT1

Transcription factors of the NFAT family play a critical role in the immune response by activating the expression of cytokines and other inducible genes in antigen-stimulated cells. Here we show that a member of this family, NFAT1, is involved in down-regulating the late phase of IL-4 gene transcription, thus inhibiting T helper 2 responses. Whereas stimulated T cells from wild-type mice show a transient increase and then a rapid decline in the steady-state levels of IL-4 mRNA in vitro, the levels of IL-4 gene transcripts in NFAT1-deficient T cells are maintained at high levels under the same conditions. Consistent with this observation, NFAT1-/- mice are more susceptible to infection with Leishmania major. This report provides evidence that NFAT proteins regulate not only the initiation but also the termination of gene transcription.

Regression by differentiation in the Sinclair swine model of cutaneous melanoma

The spontaneous regression of melanoma in Sinclair miniature swine involves the replacement of tumours by pigmented cells, hitherto interpreted as pigment-laden macrophages (PLMs). We hypothesized that these residual cells are terminally differentiated melanoma cells, not monocyte-derived macrophages. Swine melanoma explants with no regression were transplanted into severe combined immunodeficient (SCID) mice. Harvested transplant sites were examined by routine light and electron microscopy techniques. Paraffin sections were also stained with Hoeschst dye and examined by fluorescence microscopy. All but one site had completely regressed and were replaced by PLM-like cells. Hoeschst staining indicated they were of swine, not mouse, origin. The ultrastructural features of the single, partially regressed lesion demonstrated many premelanosomes in these cells. We conclude that tumour differentiation is an important mechanism of regression in the Sinclair swine melanoma model.

Differential responses in anterior pituitary luteinizing hormone (LH) content and LH beta- and alpha-subunit mRNA, and plasma concentrations of LH and testosterone, in bulls treated with the LH-releasing hormone agonist deslorelin

Anterior pituitary gland contents of LH and LH beta- and alpha-subunit mRNAs, and circulating concentrations of LH and testosterone, were determined in bulls treated with the LH-releasing hormone (LHRH) agonist deslorelin. Brahman (Bos indicus) bulls (14-month-old) were allocated to two groups and received the following: Control (n = 5), no treatment; Deslorelin (n = 4), four deslorelin implants (approximately 200 micrograms total deslorelin/day) for 36 d. Plasma concentrations of LH were higher in bulls treated with deslorelin on Day 1, had returned to typical levels by Day 8, and did not differ for control bulls and bulls treated with deslorelin from Day 8 to Day 29. Pituitary content of LH on Day 36 was reduced (P < 0.001) in bulls treated with deslorelin (33 +/- 4 ng/mg) compared with control bulls (553 +/- 142 ng/mg). Relative pituitary content of LH beta-subunit mRNA was also reduced on Day 36 in bulls treated with deslorelin (Control, 0.65 +/- 0.10; Deslorelin, 0.22 +/- 0.04; P = 0.003). However, alpha-subunit mRNA relative content did not differ (Control, 0.73 +/- 0.15; Deslorelin, 1.06 +/- 0.12; P > 0.05). Plasma concentrations of testosterone were increased over the period of the experiment in the bulls treated with deslorelin compared with control bulls. This is the first demonstration of reduced pituitary content of LH beta-subunit mRNA and LH, and unaltered content of alpha-subunit mRNA, in bulls treated with LHRH agonist. This was associated with apparently typical plasma concentrations of LH and elevated plasma testosterone. The anterior pituitary in bulls treated with LHRH agonist, therefore, undergoes classical desensitization and downregulation, but plasma LH and testosterone are not suppressed.

Blockade of T-cell activation by dithiocarbamates involves novel mechanisms of inhibition of nuclear factor of activated T cells

Dithiocarbamates (DTCs) have recently been reported as powerful inhibitors of NF-kappaB activation in a number of cell types. Given the role of this transcription factor in the regulation of gene expression in the inflammatory response, NF-kappaB inhibitors have been suggested as potential therapeutic drugs for inflammatory diseases. We show here that DTCs inhibited both interleukin 2 (IL-2) synthesis and membrane expression of antigens which are induced during T-cell activation. This inhibition, which occurred with a parallel activation of c-Jun transactivating functions and expression, was reflected by transfection experiments at the IL-2 promoter level, and involved not only the inhibition of NF-kappaB-driven reporter activation but also that of nuclear factor of activated T cells (NFAT). Accordingly, electrophoretic mobility shift assays (EMSAs) indicated that pyrrolidine DTC (PDTC) prevented NF-kappaB, and NFAT DNA-binding activity in T cells stimulated with either phorbol myristate acetate plus ionophore or antibodies against the CD3-T-cell receptor complex and simultaneously activated the binding of AP-1. Furthermore, PDTC differentially targeted both NFATp and NFATc family members, inhibiting the transactivation functions of NFATp and mRNA induction of NFATc. Strikingly, Western blotting and immunocytochemical experiments indicated that PDTC promoted a transient and rapid shuttling of NFATp and NFATc, leading to their accelerated export from the nucleus of activated T cells. We propose that the activation of an NFAT kinase by PDTC could be responsible for the rapid shuttling of the NFAT, therefore transiently converting the sustained transactivation of this transcription factor that occurs during lymphocyte activation, and show that c-Jun NH2-terminal kinase (JNK) can act by directly phosphorylating NFATp. In addition, the combined inhibitory effects on NFAT and NF-KB support a potential use of DTCs as immunosuppressants.

Anti-HIV agents. V. Synthesis, structure and in vitro anti-HIV activity of novel 1H,3H-naphtho[2',3':4,5]imidazo[1,2-c]thiazoles

A series of 1H,3H-naphtho[2',3':4,5]imidazo[1,2-c]thiazoles, TBZ analogues, was prepared in order to explore the influence on anti-HIV activity of the spatial requirements of the hydrophobic moiety fused to imidazothiazole system. In spite of a butterfly-like conformation evidenced by X-ray analysis of compound 4g, the results of in vitro screening suggest that the replacement of the benzene fused ring by the naphthyl moiety negatively influences the activity of analogous thiazolobenzimidazole derivatives, some of which are potent non-nucleoside HIV-1 RT inhibitors.

Peristaltic transport of two-layered power-law fluids

Peristaltic transport of two-layered power-law fluids in axisymmetric tubes is studied. Use of the power-law fluid model permits independent choice of shear thinning, shear thickening, or Newtonian fluids for the core and the peripheral layer. The interface between the two layers is determined from a transcendental equation in the core radius. The variation of the time-mean flow Q with the pressure rise or drop over one wavelength delta p is studied. It is observed that a negative time-mean flow is achieved under free pumping (delta p = 0) for the wave forms considered here if one of the peripheral layer and core fluids is non-Newtonian. The rheology of the peripheral layer fluid is a dominant factor in producing a negative or positive mean flow. It is noticed that a sinusoidal wave always yields a positive mean flow for power-law fluids. The trapped bolus volume for sinusoidal peristaltic wave is observed to decrease with an increase in the rate of shear thinning of the core and the peripheral layer fluids.

IKK-1 and IKK-2: cytokine-activated IkappaB kinases essential for NF-kappaB activation

Activation of the transcription factor nuclear factor kappa B (NF-kappaB) is controlled by sequential phosphorylation, ubiquitination, and degradation of its inhibitory subunit IkappaB. A large multiprotein complex, the IkappaB kinase (IKK) signalsome, was purified from HeLa cells and found to contain a cytokine-inducible IkappaB kinase activity that phosphorylates IkappaB-alpha and IkappaB-beta. Two components of the IKK signalsome, IKK-1 and IKK-2, were identified as closely related protein serine kinases containing leucine zipper and helix-loop-helix protein interaction motifs. Mutant versions of IKK-2 had pronounced effects on RelA nuclear translocation and NF-kappaB-dependent reporter activity, consistent with a critical role for the IKK kinases in the NF-kappaB signaling pathway.

Activity regulates the synaptic localization of the NMDA receptor in hippocampal neurons

We describe here a novel effect of activity on the subcellular distribution of NMDA receptors in hippocampal neurons in culture. In spontaneously active neurons, NMDA receptors were clustered at a few synaptic and nonsynaptic sites. Chronic blockade of NMDA receptor activity induced a 380% increase in the number of NMDA receptor clusters and a shift to a more synaptic distribution. This effect was reversible. The distributions of the presynaptic marker synaptophysin, the AMPA-type glutamate receptor subunit GluR1, and the putative NMDA receptor clustering protein PSD-95 were not affected by blockade. Regulation of the synaptic localization of NMDA receptors by activity may define a novel mechanism by which input controls a neuron's ability to modify its synapses.

Characteristics of dental fear amongst dental and medical students

A survey using a modification of the Dental Fear Survey (3) was carried out among 304, 17-22-year-old college students in Mangalore, India, in order to determine the prevalence and characteristics of dental fear. Feeling tense was found to be the most frequently reported physiologic arousal. Among the dental situations, the needle and the drill were the most fear-provoking stimuli. About 51% of the students reported some fear of dentistry with females and dental students being more fearful than males and medical students. They also reported higher avoidance behaviour. This study also suggested that dental fear could be influences by family and friends.

Fatal heroin body packing

The deaths of 10 heroin body packers are reported and contrasted to those of cocaine body packers. Only one was a woman, and all were traveling to or from Colombia. Drug packets deteriorated in the gastrointestinal tract and caused the deaths of eight victims. Accomplices removed drug packets from two of these smugglers after death occurred. One died of peritonitis stemming from a small-bowel obstruction caused by the drug packets, and one died from the recreational use of heroin (nasally ingested). The heroin recovered was < or = 881 g, and the drug purity of the contraband in three cases was between 65% and 73%. Blood concentrations of morphine were < 1.0 mg/L in four victims; no morphine was detected in the smuggler who died of peritonitis. However, two victims had blood morphine concentrations of 4.4 mg/L and 6.7 mg/L, respectively, and three had morphine concentrations of 35.8, 39.4, and 52.6 mg/L, respectively. Fatal heroin body packing differs from cocaine body packing in that individuals may have extremely high drug levels in their blood and their accomplices appear to be more likely to abandon them in a remote location after attempting to remove the drug packets after death has occurred.

A genetic animal model of human neocortical heterotopia associated with seizures

Malformations of the human neocortex are commonly associated with developmental delays, mental retardation, and epilepsy. This study describes a novel neurologically mutant rat exhibiting a forebrain anomaly resembling the human neuronal migration disorder of double cortex. This mutant displays a telencephalic internal structural heterotopia (tish) that is inherited in an autosomal recessive manner. The bilateral heterotopia is prominent below the frontal and parietal neocortices but is rarely observed in temporal neocortex. Neurons in the heterotopia exhibit neocortical-like morphologies and send typical projections to subcortical sites; however, characteristic lamination and radial orientation are disturbed in the heterotopia. The period of neurogenesis during which cells in the heterotopia are generated is the same as in the normotopic neocortex; however, the cells in the heterotopia exhibit a "rim-to-core" neurogenetic pattern rather than the characteristic "inside-out" pattern observed in normotopic neocortex. Similar to the human syndrome of double cortex, some of the animals with the tish phenotype exhibit spontaneous recurrent electrographic and behavioral seizures. The tish rat is a unique neurological mutant that shares several features with a human cortical malformation associated with epilepsy. On the basis of its regional connectivity, histological composition, and period of neurogenesis, the heterotopic region in the tish rat is neocortical in nature. This neurological mutant represents a novel model system for investigating mechanisms of aberrant neocortical development and is likely to provide insights into the cellular and molecular events contributing to seizure development in dysplastic neocortex.

Characterization of guanylate kinase-associated protein, a postsynaptic density protein at excitatory synapses that interacts directly with postsynaptic density-95/synapse-associated protein 90

The structure of central synapses is poorly understood at the molecular level. A recent advance came with the identification of the postsynaptic density-95 (PSD-95)/synapse-associated protein 90 family of proteins as important mediators of the synaptic clustering of certain classes of ion channels. By yeast two-hybrid screening, a novel protein termed guanylate kinase-associated protein (GKAP) has been isolated that binds to the GK-like domain of PSD-95 (). Here we present a detailed characterization of GKAP expression in the rat brain and report the cloning of a novel GKAP splice variant. By Northern blot, GKAP mRNAs (4, 6.5, and 8 kB) are expressed predominantly in the rat brain. By in situ hybridization, GKAP is expressed widely in neurons of cortex and hippocampus and in the Purkinje and granule cells of the cerebellum. On brain immunoblots, two prominent bands of 95 and 130 kDa are detected that correspond to products of short and long N-terminal splice variants of GKAP. Two independent GKAP antibodies label somatodendritic puncta in neocortical and hippocampal neurons in a pattern consistent with synaptic elements. Immunogold electron microscopy reveals GKAP to be predominantly postsynaptic and present at asymmetric synapses and in dendritic spines. The distribution of GKAP immunogold particles is uniform in the lateral plane of the PSD but peaks in the perpendicular axis approximately 20 nm from the postsynaptic membrane. In cultured hippocampal neurons GKAP immunoreactive puncta colocalize with the AMPA receptor subunit Glu receptor 1 but not with the GABAA receptor subunits beta2 and beta3. Thus GKAP is a widely expressed neuronal protein localized specifically in the PSD of glutamatergic synapses, consistent with its direct interaction with PSD-95 family proteins.

Effects of vasopressin and elimination of corticotropin-releasing hormone-target cells on pro-opiomelanocortin mRNA levels and adrenocorticotropin secretion in ovine anterior pituitary cells

Although arginine-vasopressin (AVP) is reported to produce greater ACTH biosynthetic and secretary responses than does corticotropin-releasing hormone (CRH) in sheep anterior pituitary cells, neither factor appears to increase pro-opiomelanocortin (POMC) mRNA levels, as does CRH in the cells of some other species. Since only a fraction of cells that express POMC mRNA may be able to respond to AVP, the aim of this study was to further delineate the regulation of POMC mRNA in ovine anterior pituitary corticotrophs, as a whole and in functional subpopulations of corticotrophs. We measured the effects of AVP, CRH or activation of protein kinase C by phorbol myristate acetate (PMA) in cultured cells. We compared responses in intact populations with those of cultures from which CRH-target cells were pharmacologically eliminated. Dissociated adult ovine anterior pituitary cells were cultured overnight, treated with either vehicle (intact) or a CRH-toxin conjugate that specifically eliminates CRH-target cells (CRH-target-depleted), washed, returned to culture and subsequently challenged with vehicle, AVP (100 nM), CRH (10 nM) or PMA (1 microM) for 5 h. The media were assayed for ACTH by RIA and the cells for POMC mRNA by Northern blot analysis. In intact populations, AVP and CRH increased ACTH secretion from 6.5 +/- 1.2 to 216 +/- 22 and 81 +/- 14 ng/well respectively, but only AVP caused an increase in steady-state POMC mRNA levels (+48 +/- 10%). Direct activation of protein kinase C with PMA mimicked the effect of AVP on ACTH secretion (318 +/- 16 ng/well), but did not alter POMC mRNA levels. In CRH-target-depleted populations, control ACTH secretion (11 +/- 3 ng/well) and POMC mRNA (+69 +/- 7%) were elevated, compared with intact populations. AVP (55 +/- 8 ng/well) and PMA (120 +/- 17 ng/ well), but not CRH, increased ACTH secretion; POMC mRNA was not significantly elevated by any of the treatments. Taken together, these data provide further support for the notion of dissociation between secretion of ACTH and expression of POMC mRNA, and demonstrate that AVP increases steady-state POMC mRNA levels in ovine anterior pituitary cells. The data are also consistent with the concept that complex interactions, possibly including those between cells, influence ACTH secretion and steady-state POMC mRNA levels.

Effect in supralethally irradiated rats of granulocyte colony-stimulating factor and lisofylline on hematopoietic reconstitution by syngeneic bone marrow or whole organ passenger leukocytes

We have previously shown the existence of migratory hematopoietic stem cells in adult solid organs. This study demonstrates that granulocyte colony-stimulating factor (G-CSF) and lisofylline, a phosphatidic acid inhibitor that suppresses hematopoiesis-inhibiting cytokines, can enhance the engraftment of organ-based hematopoietic stem cells. When syngeneic heart grafts or liver nonparenchymal cells were transplanted into lethally irradiated (9.5 Gy) Lewis rats, complete hematopoietic reconstitution and animal survival were significantly improved by treating the recipient with G-CSF or, to a lesser extent, with lisofylline. Pretreatment of hepatic nonparenchymal cell donors with G-CSF, but not lisofylline, also resulted in striking improvement of recipient survival which was associated with an augmented subpopulation of donor stem cells. The results suggest that these drugs can be used to enhance the chimerism that we postulate to be the basis of organ allograft acceptance.

Detailed quality of life assessment in patients treated with primary radiotherapy for squamous cell cancer of the base of the tongue

BACKGROUND

This study was conducted to evaluate quality of life in patients treated with primary radiotherapy (RT) for cancer of the base of tongue.

METHODS

From 1981 to 1990, 36 patients with primary squamous cell cancer of the base of tongue were managed with primary radiotherapy. Ages ranged from 35 to 71 years (median, 58 years), T Stage was: T1, n = 11; T2, n = 14; T3, n = 10; T4, n = 1. Thirty-one patients (86%) had palpable cervical lymph node metastases at initial examination (N1, n = 16; N2, n = 11; N3, n = 4). Patients received external beam RT to their primary site and necks, followed by a brachytherapy boost to the tongue. Those with neck nodes also had a neck dissection. The median follow-up is 5 years (minimum, 3 years). Actuarial 5-year local control was 85%; regional control was 96%; distant metastases-free survival was 87.5%; and overall survival, 85%. Twenty-nine of the 30 long-term survivors completed (1) Memorial Symptom Assessment Scale (MSAS), (2) Functional Assessment of Cancer Therapy (FACT), (3) Performance Status Scale for Head and Neck Cancer (PSS), and (4) a sociodemographic and economic questionnaire. At the time of cancer diagnosis, 62% were employed full-time, and 21% were employed part-time; 83% were earning > $20,000/year, and 59% were earning > $60,000/year.

RESULTS

At follow-up, annual incomes were similar to those at initial examination. Of those who had been working full-time, 72% were still in full-time work, and of those who had been working part-time, 83% were still in part-time work. Average PSS scores were 90 for eating in public, 96 for understandability of speech, and 68 for normalcy of diet. On the MSAS, the following symptoms had prevalence: > 30% xerostomia, difficulty swallowing, decreased energy, pain, worrying, insomnia, cough, drowsy, change in taste, and irritability. Scores on the FACT exceeded published values collected for a mixed cancer population.

CONCLUSIONS

The overwhelming majority of patients achieved excellent functional status and quality of life and could maintain their prediagnosis earning potential and employment status after primary radiation for advanced base of tongue cancer.

Chemotherapy and low-dose radiotherapy in the treatment of HIV-infected patients with carcinoma of the anal canal

PURPOSE

To determine the efficacy and tolerance of a standardized protocol of chemotherapy and low-dose radiotherapy in the treatment of anal cancer in human immunodeficiency virus (HIV)-infected patients.

METHODS AND MATERIALS

Between 1987 and 1995, eight HIV-positive patients with squamous cell carcinoma of the anal canal, four of whom had acquired immunodeficiency syndrome (AIDS), received therapy at the Kaiser Permanente Medical Center. All patients were treated using a combined modality approach consisting of low-dose radiotherapy (30 Gy in 15 fractions delivered 5 days/week), and chemotherapy [1000 mg/m2 of 5-fluorouracil (5-FU) delivered on days 1-4 and 29-32 as a continuous infusion over 96 h, and 10 mg/m2 of mitomycin C delivered as a bolus injection on day 1]. Patients have been followed from 4 to 81 months (mean 41, median 38).

RESULTS

All eight patients completed the therapy with minor variations to the protocol, and all have attained a clinical complete response. Four patients are alive and free of disease, and four died as a result of complications of AIDS, but remained free of anal carcinoma. There were no mortalities from the protocol and the morbidity was acceptable. Only one patient each was noted to have Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Grade 4 hematologic and gastrointestinal acute toxicity, and no Grade 4 skin toxicity was noted.

CONCLUSION

This combined therapy is effective for HIV-infected patients and appears to be tolerable with acceptable toxicities. It is best applied to patients who are HIV positive, or who have AIDS without concurrent major opportunistic infections. This approach is reasonable and affords patients a reasonably good chance at sphincter preservation by avoiding abdominoperineal resection. The optimal therapy for HIV-positive patients with advanced AIDS remains less well defined.

GKAP, a novel synaptic protein that interacts with the guanylate kinase-like domain of the PSD-95/SAP90 family of channel clustering molecules

The molecular mechanisms underlying the organization of ion channels and signaling molecules at the synaptic junction are largely unknown. Recently, members of the PSD-95/SAP90 family of synaptic MAGUK (membrane-associated guanylate kinase) proteins have been shown to interact, via their NH2-terminal PDZ domains, with certain ion channels (NMDA receptors and K+ channels), thereby promoting the clustering of these proteins. Although the function of the NH2-terminal PDZ domains is relatively well characterized, the function of the Src homology 3 (SH3) domain and the guanylate kinase-like (GK) domain in the COOH-terminal half of PSD-95 has remained obscure. We now report the isolation of a novel synaptic protein, termed GKAP for guanylate kinase-associated protein, that binds directly to the GK domain of the four known members of the mammalian PSD-95 family. GKAP shows a unique domain structure and appears to be a major constituent of the postsynaptic density. GKAP colocalizes and coimmunoprecipitates with PSD-95 in vivo, and coclusters with PSD-95 and K+ channels/NMDA receptors in heterologous cells. Given their apparent lack of guanylate kinase enzymatic activity, the fact that the GK domain can act as a site for protein-protein interaction has implications for the function of diverse GK-containing proteins (such as p55, ZO-1, and LIN-2/CASK).