Identification and characterization of espin, an actin-binding protein localized to the F-actin-rich junctional plaques of Sertoli cell ectoplasmic specializations

Ectoplasmic specializations are membrane-cytoskeletal assemblages found in Sertoli cells at sites of attachment to elongate spermatids or neighboring Sertoli cells. They are characterized in part by the presence of a unique junctional plaque which contains a narrow layer of parallel actin bundles sandwiched between the Sertoli cell plasma membrane and an affiliated cistern of endoplasmic reticulum. Using a monoclonal antibody, we have identified ‘espin,’ a novel actin-binding protein localized to ectoplasmic specializations. By immunogold electron microscopy, espin was localized to the parallel actin bundles of ectoplasmic specializations at sites where Sertoli cells contacted the heads of elongate spermatids. The protein was also detected at the sites of ectoplasmic specializations between neighboring Sertoli cells. Espin exhibits an apparent molecular mass of approximately 110 kDa in SDS gels. It is encoded by an approximately 2.9 kb mRNA, which was found to be specific to testis among the 11 rat organs and tissues examined. On the basis of cDNA sequence, espin is predicted to be an 836 amino acid protein which contains 8 ankyrin-like repeats in its N-terminal third, a potential P-loop, two proline-rich peptides and two peptides which contain clusters of multiple glutamates bracketed by arginines, lysines and glutamines in a pattern reminiscent of the repetitive motif found in the protein trichohyalin. The ankyrin-like repeats and a 66 amino acid peptide in the C terminus show significant sequence similarity to proteins encoded by the forked gene of Drosophila. A fusion protein containing the C-terminal 378 amino acids of espin was found to bind with high affinity (Kd = approximately 10 nM) to F-actin in vitro with a stoichiometry of approximately 1 espin per 6 actin monomers. When expressed by transfected NRK fibroblasts, the same C-terminal fragment of espin was observed to decorate actin fibers or cables. On the basis of its structure, localization and properties, we hypothesize that espin is involved in linking actin filaments to each other or to membranes, thereby potentially playing a key role in the organization and function of the ectoplasmic specialization.

Integrated genetic map of Anopheles gambiae: use of RAPD polymorphisms for genetic, cytogenetic and STS landmarks

Randomly amplified polymorphic DNA (RAPD) markers have been integrated in the genetic and cytogenetic maps of the malaria vector mosquito, Anopheles gambiae. Fifteen of these markers were mapped by recombination, relative to microsatellite markers that had been mapped previously. Thirty-four gel-purified RAPD bands were cloned and sequenced, generating sequence tagged sites (STSs) that can be used as entry points to the A. gambiae genome. Thirty one of these STSs were localized on nurse cell polytene chromosomes through their unique hybridization signal in in situ hybridization experiments. Five STSs map close to the breakpoints of polymorphic inversions, which are notable features of the Anopheles genome. The usefulness and limitations of this integrated mosquito map are discussed.

Synaptic organization of damaged infraorbital nerve axons in perinatal rats: demonstration by galanin immunocytochemistry

Neonatal transection of the infraorbital nerve (ION; the trigeminal, V, branch that supplies the mystacial vibrissae follicles) results in an upregulation of galanin in the central arbors of primary afferent axons. The present study was undertaken to evaluate the synaptic organization of these galanin-positive primary afferents and compare it with that of normal neurobiotin/biocytin-labeled primary afferent axons from animals of the same age. Examination of 1200 neurobiotin/biocytin-labeled profiles in V nucleus principalis (PrV) of rats killed on postnatal day (P-) 7 indicated that 23.3% (n = 279) of these profiles made synaptic contacts: 87.4% were axodendritic, 8.9% were axoaxonic, 2.8% were axosomatic, and 0.7% were axospinous. Evaluation of 1200 galanin-positive profiles in PrV from rats that sustained transection of the ION on P-0 and were killed on P-7 indicated that only 64 (5.3%) of these profiles made synaptic contacts (P < 0.05 compared with the intact animals). Of the galanin-positive profiles that did make synapses in PrV, 81.2% (n = 52) were axodendritic and 18.8% (n = 12) were axoaxonic. These results indicate that galanin released by damaged ION primary afferents in PrV is likely to affect the activity of second-order V neurons by a paracrine action rather than by acting at specific synapses.

Leukotriene D4-induced mobilization of intracellular Ca2+ in epithelial cells is critically dependent on activation of the small GTP-binding protein Rho

We have previously shown that the leukotriene D4 (LTD4)-induced mobilization of intracellular Ca2+ in epithelial cells is mediated by a G-protein that is distinctly different from the pertussis toxin-sensitive G-protein that regulates the subsequent influx of Ca2+. In the present study, we attempted to gain further knowledge about the mechanisms involved in the LTD4-induced mobilization of intracellular Ca2+ in epithelial cells by investigating the effects of compactin, an inhibitor of the isoprenylation pathway, on this signalling event. In cells preincubated with 10 microM compactin for 48 h, the LTD4-induced mobilization of intracellular Ca2+ was reduced by 75% in comparison with control cells. This reduction was reversed by co-administration of mevalonate (1 mM). The effect of compactin occurred regardless of whether or not Ca2+ was present in the extracellular medium, suggesting that isoprenylation must occur before Ca2+ is released from intracellular stores. In accordance with this, we also found that both the LTD4-induced formation of inositol 1,4,5-trisphosphate and the LTD4-induced phosphorylation of phospholipase C gamma 1 (PLC gamma 1) on tyrosine residues were significantly reduced in compactin-pretreated cells. These results open up the possibility that the activation of PLC gamma 1 is related to a molecule that is sensitive to impaired activity of the isoprenylation pathway, such as a small monomeric G-protein. This idea was supported by the observation that Clostridium botulinum C3 exoenzyme-induced inhibition of Rho proteins abolished the LTD4-induced intracellular mobilization of Ca2+. A regulatory role of Rho proteins in the LTD4-induced activation of PLC gamma 1 is unlikely to be indirectly mediated via an effect on the cytoskeleton, since cytochalasin D had no major effect on the LTD4-induced mobilization of Ca2+. Although the mechanism of interaction remains to be elucidated, the present findings indicate an important role of an isoprenylated protein such as Rho in the LTD4-induced Ca2+ signal.

Paralytic shellfish poisoning in southern China

The rapidly expanding mariculture and commercial region along the southern coast of China has experienced sporadic outbreaks of paralytic shellfish poisoning for nearly 30 years, yet virtually nothing is known of the nature of that toxicity or of the causative organisms. This study presents the first direct comparisons of the high performance liquid chromatography toxin composition profiles of shellfish implicated in paralytic shellfish poisoning outbreaks in Daya Bay with Alexandrium tamarense cultures established from those waters. The three cultures that were analyzed produced an unusually high proportion of the low potency N-sulfocarbamoyl toxins C1 and C2 (nearly 90% of the total), and only trace quantities of the other saxitoxin derivatives. Total toxicity was thus very low with mild acid extraction, ranging between 7.2 and 12.7 fmole cell-1, or 0.7-0.9 pg saxitoxin equiv. cell-1. Following acid hydrolysis using the standard AOAC extraction method, the dominant toxins in the cultures were gonyautoxins 2 and 3 and decarbamoyl gonyautoxins 2 and 3. Total potency increased fourfold to 2.6-3.4 pg saxitoxin equiv. cell-1 following acid hydrolysis. These cultures are thus at the low end of the range of toxicities recorded for members of the A. tamarense species complex. Two scallop samples and one mussel sample collected from Daya Bay during paralytic shellfish poisoning episodes in 1990 and 1991 were also analyzed following the AOAC extraction procedure. The toxin profiles were similar for the three shellfish samples, in that the same suite of toxins were present in each, but the relative proportion of those toxins varied. The dominant toxins were gonyautoxins 2 and 3 and toxins C1-C4. Total toxicity was 336 and 654 micrograms saxitoxin per 100 g meat for the scallop samples, and 723 for the mussels. Toxins C3,4 were present in the shellfish at up to 22 mole%, but were not detected in cultures, even when mild acid was used for extraction. Despite the otherwise similar nature of the culture versus the shellfish toxin signatures, the presence of C3,4 indicates that another strain or species of Alexandrium, or possibly a paralytic shellfish poisoning-producing species of another genus was responsible for the 1990 and 1991 paralytic shellfish poisoning outbreaks in Daya Bay. Since the cultures analyzed were of low intrinsic toxicity, A. tamarense may be more widespread along the south coast of China than is suggested by the sporadic pattern of past paralytic shellfish poisoning outbreaks. Blooms with high cell density are required to generate sufficient toxin to be dangerous. The alarming increase in algal blooms in Chinese waters due to persistent and growing pollution may make these low toxicity populations more problematic in the future.

Reliability of self-reported human immunodeficiency virus risk behaviors in a residential drug treatment population

This study examined test-retest reliabilities of self-reported human immunodeficiency virus (HIV) sexual and drug injection behaviors among 246 prior drug users admitted to either of two residential drug treatment programs in Westborough, Massachusetts, and Providence, Rhode Island, between June 1990 and September 1992. Participants, selected by their date of admission, were administered admission and reliability questionnaires pertaining to HIV risk behaviors, the latter at approximately 2 weeks after admission. Estimated reliabilities (kappa coefficients) of the sexual behaviors ranged from 0.72 to 0.91; those for the drug injection variables ranged from 0.63 to 0.98. These results were consistent across groups defined by sex and injection of drugs. The consistently good reliabilities are significant to the design of independent studies of drug treatment populations utilizing self-report measures of sexual and drug behaviors.

[Intracranial fungal granuloma with CSF space dissemination: a case report]

A 28-year-old male presented with a low grade fever, decreased activity, left hemiparesis and signs of intracranial hypertension. CT showed a moderate hydrocephalus and a large irregular mass in the right temporoparietal region with garland-like enhancement after injection of the contract medium. These findings suggested a malignant brain tumor. MR images demonstrated a mass with low-iso signal intensity on T1 weighted image and low-iso-high mixed intensity on T2, which is like a mosaic pattern. Multiple cerebrospinal fluid space seedings including the wall of the lateral ventricle, the surface of the cerebellum and pons, and the cervical spinal cord were clearly delineated on MR images after Gd-DTPA injection. The large mass was totally removed by craniotomy after ventricle drainage for hydrocephalus. Microscopic examinations showed dense fibrous connective tissue with infiltration of Langhans' giant cells, lymphocytes and fibroblasts around the necrotic centers. These hard components may have been responsible for the low signal intensity on T2-MR images. Many Candida elements were clearly shown with the periodic acid Schiff stain. The diagnosis was that the lesion was an intraparenchymal granuloma due to Candida infection. The patient died on the 8th postoperative day because of brain stem malfunction. Intracranial fungal infection rarely produces a granuloma in the central nervous system. Though it is difficult to diagnose a large irregular mass in the brain, MR images, especially T2 weighted images are useful for the diagnosis of fungal granuloma.

The LIM domain-containing Dbm1 GTPase-activating protein is required for normal cellular morphogenesis in Saccharomyces cerevisiae

Normal cell growth in the yeast Saccharomyces cerevisiae involves the selection of genetically determined bud sites where most growth is localized. Previous studies have shown that BEM2, which encodes a GTPase-activating protein (GAP) that is specific for the Rho-type GTPase Rho1p in vitro, is required for proper bud site selection and bud emergence. We show here that DBM1, which encodes another putative Rho-type GAP with two tandemly arranged cysteine-rich LIM domains, also is needed for proper bud site selection, as haploid cells lacking Dbm1p bud predominantly in a bipolar, rather than the normal axial, manner. Furthermore, yeast cells lacking both Bem2p and Dbm1p are inviable. The nonaxial budding defect of dbm1 mutants can be rescued partially by overproduction of Bem3p and is exacerbated by its absence. Since Bem3p has previously been shown to function as a GAP for Cdc42p, and also less efficiently for Rho1p, our results suggest that Dbm1p, like Bem2p and Bem3p, may function in vivo as a GAP for Cdc42p and/or Rho1p. Both LIM domains of Dbm1p are essential for its normal function. Point mutations that alter single conserved cysteine residues within either LIM domain result in mutant forms of Dbm1p that can no longer function in bud site selection but instead are capable of rescuing the inviability of bem2 mutants at 35 degrees C.

[Relationship between cellular DNA and expression of epidermal growth factor receptor in pleomorphic adenoma of lacrimal gland]

OBJECTIVE

To obtain the information about whether expression of epidermal growth factor (EGF) receptor is related to the proliferative activity of tumor.

METHODS

The expression of EGF receptor and DNA content of pleomorphic adenoma of lacrimal gland in 32 cases were detected by an immunohistochemical avidin biotin peroxidase complex method and determined by an image analysis technique, respectively. The relationship between the expression of EGF receptor and DNA content was analyzed.

RESULTS

10 tumors were stained positively with anti-EGF receptor antibody, the DNA contents of 14 cases were increased, their DNA ploidy distribution pattern showed two or several peaks. Good correlation has been found between the expression of EGF receptor and DNA ploidy distribution pattern, and the DNA distribution pattern of tumor with positive EGF receptor expression showed mainly two or several peaks (P < 0.01).

CONCLUSION

The expression of EGF receptor of pleomorphic tumor of lacrimal gland is related to the proliferative activity of tumor cells.

Increased serotonin in the developing superior colliculus does not alter the number or distribution of retinotectal ganglion cells

Administration of a single subcutaneous dose of 5,7-dihydroxytryptamine (5,7-DHT) to newborn hamsters results in a significant increase in the density of serotoninergic (5-HT) fibers in the superficial layers of the superior colliculus (SC) and marked abnormalities in both the crossed and uncrossed retinotectal projections when these animals reach adulthood (R. Rhoades, C. Bennett-Clarke, R. Lane, M. Leslie, and R. Mooney, 1993, J. Comp. Neurol. 334:397-409). The present study was undertaken to determine whether changes in the retinotectal projection of 5,7-DHT-treated animals were associated with alterations in the number or distribution of retinal ganglion cells in these animals. Nissl staining of retinae from normal adult and 5,7-DHT-treated hamsters revealed no differences between them in the number or average diameter of cells in the retinal ganglion cell layer. Retrograde labeling with horseradish peroxidase (HRP) demonstrated no effect of 5,7-DHT treatment on the number or distribution of ipsilaterally or contralaterally projecting ganglion cells. Neonatal 5,7-DHT administration also had no effect on the distribution of soma diameters for HRP-labeled retinal ganglion cells. Electron microscopic analysis demonstrated no significant difference between the number of optic nerve fibers in the normal and 5,7-DHT-treated hamsters. The results are consistent with the conclusion that the effect of 5,7-DHT on the retinotectal projection may primarily be a function of this toxin, or the increase in 5-HT it induces, on the terminal arbors of retinotectal axons rather than on their parent cells.

[In vitro culture of neonatal mouse calvaria as a model for study of bone resorption]

We established the in vitro culture system of neonatal mouse calvaria. Bone resorption was determined by the following examinations; (1) the release of calcium from the calvaria into the medium was measured by use of atomic absorption spectrophotometer, and the treated to control ratio was calculated and used as an index of bone resorption; (2) the concentration of osteocalcin in the cultured medium was determined by radioimmunoassay; (3) histological examination. By combined use of the examinations, we were able to objectively determine the bone resorption of cultured calvaria.

[Investigation of infiltrating lymphocytes and immunoglobulin by immunohistochemical method in cheilitis granulomatosa]

Category and distribution of infiltrating lymphocytes and immunoglobulin in 12 cases with cheilitis granulomatosa (CG) and 4 cases with Melkersson-Rosenthal syndrome (MRS) were investigated. The result was that infiltration of lymphocytes in granulomatous type was more severe than that in interstitial inflammtion type. Infiltrators mainly consisted of T helper lymphocytes and immunoglobulin was IgM. It was considered that local immunoreaction was enhanced suggesting that cyto-immunity was a dominant factor with participation of humoral immunity. The result will be helpful to elucidate the pathogeneses and the function of many immuno-factors in the CG. It helps to understand the clinical manifestations and may be a theoretic reference for seeking immuno-modulation for treatment.

Increased soluble CD14 levels in BAL fluid in pulmonary tuberculosis

INTRODUCTION

CD14 is a cell surface glycoprotein expressed mainly on mature monocytes and macrophages. Soluble CD14 (sCD14) is present in normal plasma and is found increased in serum of patients with septicemia, polytrauma, and sarcoidosis. In active sarcoidosis, increased levels of sCD14 in BAL supernatant have been demonstrated.

STUDY OBJECTIVE

To investigate sCD14 levels in BAL of pulmonary tuberculosis (PTB), another inflammatory disease characterized by granuloma formation.

METHODS

BAL was performed in 12 patients with active but untreated PTB and 12 healthy persons. Cytologic and immunocytologic characteristics were determined. sCD14 was measured by a sandwich enzyme-linked immunosorbent assay.

RESULTS

The level of sCD14 in patients with PTB was increased compared with controls (mean +/- SEM: 34.4 +/- 9.6 ng/mL vs 11.5 +/- 2.2 ng/mL; p = 0.02). No correlation was found between sCD14 levels and BAL cell differentials or lymphocyte surface markers.

CONCLUSION

Similar to sarcoidosis, increased levels of sCD14 are found in BAL supernatant of PTB patients.

[Detection of FMR-1 gene expression by RT-PCR]

Fragile X syndrome [FRA(X)] as the most common form of inherited mental retardation in man has an incidence of one per 1250 and is associated with a fragile site at Xq27.3. A gene was identified at the fragile X locus and was designated Fragile X Mental Retardation-1 (FMR-1). FRA(X) resulted from expansion of (CGG)n trinucleotide repeat in 5' untranslated region of the human FMR-1 gene, and was associated with abnormal methylation of a CpG island 250 bp proximal to this (CGG)n repeat. Males with typical FRA(X) showed repression of FMR-1 transcription and absence of FMR-1 protein, which was believed to contribute to the fragile X phenotype. FMR-1 mRNA extracted from leukocytes in normal and clinically suspected males were detected by RT-PCR. The methylation status and CGG expansion were also studied by PCR and Southern blot. Two of 10 clinically suspected males were found devoid of FMR-1 expression and accompanied with hypermethylation of the CpG island and CGG trinucleotide repeat expansion.

Two genes encoding midgut-specific maltase-like polypeptides from Anopheles gambiae

Full-length cDNA clones of two genes have been isolated from the African malaria vector mosquito, Anopheles gambiae. These genes, designated Agm1 and Agm2, encode maltase-like polypeptides of 498 and 599 residues, respectively. Deduced amino acid sequences contain a putative signal peptide sequence and four potential glycosylation sites. Agm1 and Agm2 show highest similarities to the Mal1 gene from Aedes aegypti and three clustered maltase genes from Drosophila melanogaster. Both genes are located at position 46D, in the terminal division of the left arm of the third chromosome. Agm2 has very strict tissue and temporal specificity, being expressed exclusively in the adult midgut. The specificity of Agm1 is similar but appears slightly broader; transcripts of this gene are detected at a low level in the pupae, and occasionally in the adult carcass after removal of the midgut.

[Pathologic observations of hepatitis C]

The morphological changes in liver biopsies from 70 patients with a clinical diagnosis of hepatitis C were studied. Sixty-two of the patients had history of blood transfusions. All patients were seropositive for anti-HCV by first and second generation test and/or were seropositive for HCV RNA by PCR method. Clinically, twenty cases diagnosed as acute hepatitis, fifty were chronic including 7 cases with both HBV and HCV infection. The main morphological changes in acute cases being 1. Focal degeneration of liver cells, including large and small droplet fatty changes. 2. Focal necrosis and acidophilic bodies usually being surrounded by T lymphocytes. 3. Sinusoidal inflammatory cell infiltration. 4. Lymphoid aggregation with bile duct epithelial damage was found in 60% of portal tracts. The chronic cases included 17 chronic persistent hepatitis cases (CPH) and 33 chronic active hepatitis cases (CAH). The main histopathologic changes in CAH included dense clusters of lymphocytes (lymphoid aggregates) present in the enlarged portal tracts with bridging necrosis and fibrosis, lobular inflammation including acidophilic bodies, focal necrosis and fatty degeneration. The sinusoidal cells were often hyperplastic. These changes may provide useful diagnostic clues for hepatitis C.

Induction of apoptosis in mature T cells by tumour necrosis factor

T-cell receptor-induced apoptosis regulates immune responses and can result from interactions between Fas (Apo1/CD95) and Fas ligand (FasL). Mutations in the genes for Fas and FasL cause disorders resembling human autoimmune diseases in lpr and gld mice, respectively. However, peripheral T-cell deletion takes place in lpr mice, and autoimmune syndromes occur in mouse strains without Fas or FasL defects. Here we show that tumour necrosis factor (TNF) can mediate mature T-cell receptor-induced apoptosis through the p75 TNF receptor. Blockage of both TNF and FasL is required to abrogate T-cell death and TNF mediates the death of most CD8+ T cells, whereas FasL mediates the death of most CD4+ T cells. Our results suggest that autoregulatory apoptosis of the mature T cells can occur by two distinct molecular mechanisms.

Temporal and spatial expression of amygdalin hydrolase and (R)-(+)-mandelonitrile lyase in black cherry seeds

In black cherry (Prunus serotina Ehrh.) macerates, the cyanogenic diglucoside (R)-amygdalin undergoes stepwise degradation to HCN catalyzed by amygdalin hydrolase (AH), prunasin hydrolase, and (R)-(+)-mandelonitrile lyase (MDL). A near full-length AH cDNA clone (pAH1), whose insert encodes the isozyme AH I, has been isolated and sequenced. AH I exhibits several features characteristic of beta-glucosidases of the BGA family, including their likely nucleophile center (isoleucine-threonine-glutamic acid-asparagine-glycine) and acid catalyst (asparagine-glutamic acid-proline/isoleucine) motifs. The temporal expression of AH and MDL in ripening fruit was analyzed by northern blotting. Neither mRNA was detectable until approximately 40 days after flowering (DAF), when embryos first became visible to the naked eye. Both mRNAs peaked at approximately 49 DAF before declining to negligible levels when the fruit matured (82 DAF). Taken together with enzyme activity data, these time courses suggest that AH and MDL expression may be under transcriptional control during fruit maturation. In situ hybridization analysis indicated that AH transcripts are restricted to the procambium, whereas MDL transcripts are localized within cotyledonary parenchyma cells. These tissue-specific distributions are consistent with the major locations of AH and MDL protein in mature seeds previously determined by immunocytochemistry (E. Swain, C.P. Li, and J.E. Poulton [1992] Plant Physiol 100:291-300).

Alveolar macrophage TNF-alpha release and BAL cell phenotypes in sarcoidosis

The aim of this study was to investigate the relationship between release of tumor necrosis factor-alpha (TNF-alpha) by alveolar macrophages (AM) and the phenotypic characteristics of bronchoalveolar lavage (BAL) cells in sarcoidosis. We studied the spontaneous release of TNF-alpha by AM in vitro and the phenotypic characteristics of freshly recovered BAL T-cells and AM in 31 individuals (13 with active sarcoidosis, nine with inactive sarcoidosis, and nine normal controls). TNF-alpha was measured by enzyme-linked immunosorbent assay (ELISA) in supernatants from unstimulated AM after 24 h culture. Phenotypic markers of BAL cells were determined by an immunocytochemical assay. AM of patients with active sarcoidosis released more TNF-alpha (1,355 +/- 133 pg/ml/ 10(6) AM/24 h) than those of the inactive group (651 +/- 142 pg/ml/10(6) AM/24 h) or the normal controls (425 +/- 121 pg/ml/10(6) AM/24 h), with p < 0.001 for both comparisons. The amount of TNF-alpha released correlated positively with the percentage expression of CD4 (r = 0.72) and CD25 (r = 0.70) by lymphocytes, and of CD14 (r = 0.63), VLA-4 (r = 0.59), FRD1 (r = 0.67) and 27E10 (r = 0.67) by AM, with p < 0.001 for all correlations. In conclusion, this relationship suggests that these antigens may be considered as cellular activation markers, and that some of these AM antigens may indirectly characterize the AM phenotype that is capable of producing TNF-alpha.

frizzled regulates mirror-symmetric pattern formation in the Drosophila eye

Coordinated morphogenesis of ommatidia during Drosophila eye development establishes a mirror-image symmetric pattern across the entire eye bisected by an anteroposterior equator. We have investigated the mechanisms by which this pattern formation occurs and our results suggest that morphogenesis is coordinated by a graded signal transmitted bidirectionally from the presumptive equator to the dorsal and ventral poles. This signal is mediated by frizzled, which encodes a cell surface transmembrane protein. Mosaic analysis indicates that frizzled acts non-autonomously in an equatorial to polar direction. It also indicates that relative levels of frizzled in photoreceptor cells R3 and R4 of each ommatidium affect their positional fate choices such that the cell with greater frizzled activity becomes an R3 cell and the cell with less frizzled activity becomes an R4 cell. Moreover, this bias affects the choice an ommatidium makes as to which direction to rotate. Equator-outwards progression of elav expression and expression of the nemo gene in the morphogenetic furrow are regulated by frizzled, which itself is dynamically expressed about the morphogenetic furrow. We propose that frizzled mediates a bidirectional signal emanating from the equator.

Analysis of the CD4 coreceptor and activation-induced costimulatory molecules in antigen-mediated mature T lymphocyte death

We have compared the signaling requirements for activation and lymphokine production in mature T lymphocytes to those required for TCR-driven programmed cell death (PCD). Both processes require TCR engagement and ligation of the CD4 coreceptor in the case of a T cell clone that recognizes Ag in the context of an MHC class II molecule. By contrast, stimulation through the CD28/B7 pathway does not appear to positively or negatively influence TCR-induced PCD, although it was required for IL-2 production in both resting and proliferating T cells. T cells that had been activated and induced to proliferate with IL-2 were found to express high levels of IL-2 mRNA upon TCR rechallenge, without a requirement for accessory cells. This was due to a strong up-regulation of the B7-1 molecule, but not the B7-2 molecule, on the T cell surface. These T cells that strongly costimulate each other are highly susceptible to TCR-induced death providing independent evidence that costimulatory signals are not protective. Thus, these results provide evidence that in mature T cells there exists a difference in the requirement for CD28 to achieve activation and IL-2 production compared with TCR-mediated PCD.

Analysis of the CD4 coreceptor and activation-induced costimulatory molecules in antigen-mediated mature T lymphocyte death

We have compared the signaling requirements for activation and lymphokine production in mature T lymphocytes to those required for TCR-driven programmed cell death (PCD). Both processes require TCR engagement and ligation of the CD4 coreceptor in the case of a T cell clone that recognizes Ag in the context of an MHC class II molecule. By contrast, stimulation through the CD28/B7 pathway does not appear to positively or negatively influence TCR-induced PCD, although it was required for IL-2 production in both resting and proliferating T cells. T cells that had been activated and induced to proliferate with IL-2 were found to express high levels of IL-2 mRNA upon TCR rechallenge, without a requirement for accessory cells. This was due to a strong up-regulation of the B7-1 molecule, but not the B7-2 molecule, on the T cell surface. These T cells that strongly costimulate each other are highly susceptible to TCR-induced death providing independent evidence that costimulatory signals are not protective. Thus, these results provide evidence that in mature T cells there exists a difference in the requirement for CD28 to achieve activation and IL-2 production compared with TCR-mediated PCD.

Mechanisms of transport of quinapril in Caco-2 cell monolayers: comparison with cephalexin

PURPOSE

To determine the transport mechanisms of quinapril and cephalexin in Caco-2 cell monolayers, a cell culture model of the human small intestinal epithelium.

METHODS

Uptake, transepithelial transport and intracellular accumulations of these two drugs were measured using Caco-2 cell monolayers grown onto Millicells and magnetically stirred diffusion chambers.

RESULTS

Transepithelial transport, apical (AP)4 uptake and intracellular accumulation of both drugs depended on the maintenance of a transepithelial proton gradient and temperature of the medium. However, quinapril transport and accumulation, which did not display a maximum at approximately pH 6, was more sensitive to proton gradient change, whereas cephalexin transport was more sensitive to concentration change (range 0.5-5 mM). In addition, quinapril (1 mM) transport was decreased significantly (p < 0.05) by 10 mM cephalexin, loracarbef, Gly-Pro and Phe-Pro, but not by enalapril; whereas cephalexin (0.1 mM) transport was decreased significantly (p < 0.05) by all four compounds. Similarly, AP quinapril (1 mM) uptake was also decreased by 10 mM loracarbef, Gly-Pro, cephalexin, and enalapril, but these inhibitory effects (20-50%) were quantitatively less than their inhibitory effects on cephalexin uptake (50-90%). Finally, the AP uptake of quinapril was also significantly (p < 0.05) inhibited by FCCP (10 micrograms/ml), amiloride (0.5 mM), DEP (0.5 mM), and staurosporine (5 nM).

CONCLUSIONS

The transport of quinapril in the Caco-2 cells is via a combination of the carrier-mediated proton gradient-dependent peptide transporter and passive diffusion.

Influence of thyroid status on postnatal maturation of calcium channels, beta-adrenoceptors and cation transport ATPases in rat ventricular tissue

In order to examine the influence of thyroid hormones on the postnatal development of cardiac excitation-contraction coupling, newborn rats were made hypo- or hyperthyroid, and several key factors involved, directly or indirectly, in Ca2+ signaling: L-type Ca2+ channels (1,4-dihydropyridine receptors), Ca(2+)-release channels of sarcoplasmic reticulum (ryanodine receptors), beta-adrenoceptors, thapsigargin-sensitive Ca(2+)-ATPase and Na(+)-K(+)-ATPase (enzyme activity and ouabain receptors), were investigated in membrane fractions from ventricular tissue, collected on day 21. Hypothyroidism induced a moderately lower myocardial density of 1,4-dihydropyridine and ryanodinerece receptors (reduced by 23% and 31%, respectively, with respect to euthyroid controls), and much reduced levels of beta-adrenoceptors, Ca(2+)-ATPase and Na(+)-K(+)-ATPase activities. Hyperthyroidism induced only a moderate (22%) decrease in the myocardial density of 1,4-dihydropyridine receptors and a marked (240%) increase of the alpha 2 isoform of Na(+)-K(+)-ATPase. To analyse the subsarcolemmal localization of L-type channels, microsomal fractions were subfractionated by density equilibration in sucrose gradient. In gradients from control and hyperthyroid rats, most 1,4-dihydropyridine receptors were recovered in high-density subfractions, their distribution following that of ryanodine receptors, whereas, in gradients from hypothyroid rats, most 1,4-dihydropyridine receptors were recovered in low-density subfractions, together with beta-adrenoceptors and Na(+)-K(+)-ATPase. We conclude that thyroid hormones are important for the postnatal changes in the myocardial density of several channels and pumps involved in Ca2+ fluxes, as well as for the postnatal redistribution of L-type Ca2+ channels from non-junctional sarcolemma to junctional structures, a key process for the efficient operation of excitation-contraction coupling in adult ventricular tissue.

[Trigeminal neuralgia caused by microvascular compression of perforation type]

Of 512 patients of trigeminal neuralgia who had undergone microvascular decompression through a retromastoid craniotomy, 4 were caused by microvascular compression of perforation type. In 3 patients, the perineurium of trigeminal nerve was cut longitudinally, the nerve-tract was separated, the perforating blood vessel was pushed to the distal end, and the vessel was made to leave the nerve sensitive area and then decompression materials were put between the separated nerve-tract. The patients were pain-free and the facial sensation was preserved after operation, and no recurrence occurred in 1 to 3 years after operation. The authors realized that there is a sensitive area near the trigeminal nerve sensory root entry zone. When the blood vessel compresses the sensitive area, trigeminal neuralgia is induced, whereas the vessel decompresses the area, the pain is free. So it is a good evidence for the microvascular compression theory and it is more important than the non-perforation type.

Cyclosporin A, rapamycin and FK506 decrease prolactin release from rat pituitary cells in primary culture

It is at present well established that prolactin exerts a non-specific immunoactivating function. In this work we tested whether the immunosuppressant drugs cyclosporin A, FK506 and rapamycin influence prolactin release from rat pituitary cells in primary culture. The tested drugs had no effect on the prolactin release measured during a 2h incubation period, indicating that they do not influence the secretion of prolactin from intracellular stores into the culture medium. During longer incubation times (48h), however, prolactin release was diminished to 56% +/- 18 (10 microM cyclosporin A), 64% +/- 14 (1 microM rapamycin) or 64% +/- 7 (1 microM FK506), suggesting an effect on prolactin production. At these drug concentrations no toxic effects were observed. The data indicate that inhibition of pituitary prolactin synthesis might contribute to the immunosuppressant action of cyclosporin A, rapamycin and FK506.

Gonadotropin-releasing hormone-induced sensitization of calcium-dependent exocytosis in pituitary gonadotrophs

Agonist-induced increases in cytoplasmic calcium concentration ([Ca2+]i) play a pivotal role in regulated exocytosis by promoting the fusion of secretory vesicles with the plasma membrane. In permeabilized and ATP-primed pituitary cells, increases in ambient [Ca2+]i stimulated the release of LH from gonadotrophs with an EC50 of 2-3 microM. In contrast, the responses of intact gonadotrophs to agonist stimulation by GnRH were characterized by transient [Ca2+]i elevations of up to 1.5 microM, followed by a plateau of 300-400 nM. The sensitivity of the exocytotic response of permeabilized cells to [Ca2+]i was significantly increased by GnRH, which reduced the EC50 for [Ca2+]i to the submicromolar concentration range. The stimulatory action of GnRH on LH release in permeabilized cells was not a consequence of intracellular Ca2+ release, but was associated with increased cytidine diphosphate diacylglycerol production. Activation of protein kinase C by phorbol esters caused a similar increase in the Ca2+ sensitivity of LH release from permeabilized cells, and this effect was not additive to that of GnRH. Furthermore, the GnRH-induced increase in the sensitivity of the exocytotic response to Ca2+ was attenuated by inhibitors of protein kinase C. These findings indicate that although elevated [Ca2+]i per se can promote LH release from permeabilized gonadotrophs, concomitant activation of protein kinase C is necessary to support exocytosis at the physiological [Ca2+]i levels that prevail in GnRH-stimulated intact cells. Such sensitization of the Ca(2+)-dependent secretory mechanism by protein kinase C may be an important step in the agonist-induced release of LH from pituitary gonadotrophs.

Dependence of stimulus-transcription coupling on phospholipase D in agonist-stimulated pituitary cells

Stimulation of phospholipase D activity is frequently observed during agonist activation of Ca(2+)-mobilizing receptors, but the cellular functions of this signaling pathway are not well defined. Pituitary gonadotrophs express Ca(2+)-mobilizing receptors for gonadotropin-releasing hormone (GnRH) and endothelin (ET), activation of which stimulates luteinizing hormone secretion and transient expression of c-fos. In pituitary cells and alpha T3-1 gonadotrophs, GnRH action was associated with both initial and sustained diacylglycerol (DG) production, whereas ET-1 induced only a transient DG response. Also, phospholipase D activity, estimated by the production of phosphatidylethanol from phosphatidylcholine in the presence of ethanol, was stimulated by GnRH but not ET-1. Such formation of phosphatidylethanol at the expense of phosphatidic acid (PA) during GnRH-induced activation of phospholipase D significantly reduced the production of PA, DG, and cytidine diphosphate diacylglycerol. Inhibition of PA-phosphohydrolase activity by propranolol also decreased GnRH-induced DG production and, in contrast to ethanol, increased PA and cytidine diphosphate diacylglycerol levels. The fall in DG production caused by ethanol and propranolol was accompanied by inhibition of GnRH-induced c-fos expression, whereas agonist-induced luteinizing hormone release was not affected. In contrast to their inhibitory actions on GnRH-induced early gene expression, neither ethanol nor propranolol affected ET-1-induced c-fos expression, or GnRH- and ET-1-induced inositol trisphosphate/Ca2+ signaling. These findings demonstrate that phospholipase D participates in stimulus-transcription but not stimulus-secretion coupling, and indicate that DG is the primary signal for this action.

Role of protein kinase C isozymes in Fc gamma receptor-mediated intracellular killing of Staphylococcus aureus by human monocytes

Intracellular killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma R is known to be a phospholipase C (PLC)-dependent process. Activation of PLC leads to the formation of second messengers that synergistically activate protein kinase C (PKC). The aim of this study was to obtain more insight into the role of PKC in Fc gamma R-mediated killing process. PKC inhibitors H-7 and staurosporine markedly suppressed the killing of S. aureus by monocytes stimulated by cross-linking Fc gamma RI or -II. Cross-linking Fc gamma R caused a transient increase in PKC activity in the membranes of monocytes, as measured by Ca2+/phospholipid-dependent phosphorylation of histone. Western blot analysis revealed that cross-linking Fc gamma R stimulated a transient increase in PKC-beta in the membranes of monocytes with kinetics that correlated closely with the translocation of PKC activity. Cross-linking Fc gamma R on monocytes also stimulated the translocation of PKC-epsilon but not PKC-alpha. PMA and 1-oleoyl-2-acetylglycerol (OAG), which caused translocation of PKC-alpha, -beta, and -epsilon, did not stimulate the killing process. Incubation with these PKC activators for 10 min rendered monocytes unresponsive to stimulation of killing of S. aureus via Fc gamma R. It could be that activation of certain PKC isozymes, probably PKC-alpha and -epsilon, by these activators causes feedback inhibition of PLC and, consequently, the killing in monocytes, because PMA blocks the Fc gamma R-mediated intracellular inositol(1,4,5)P3 formation and PKC translocation. Together, our results indicate that PKC isozymes play an important role in both stimulation and inhibition of the Fc gamma R-mediated intracellular killing of bacteria by monocytes.

Role of protein kinase C isozymes in Fc gamma receptor-mediated intracellular killing of Staphylococcus aureus by human monocytes

Intracellular killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma R is known to be a phospholipase C (PLC)-dependent process. Activation of PLC leads to the formation of second messengers that synergistically activate protein kinase C (PKC). The aim of this study was to obtain more insight into the role of PKC in Fc gamma R-mediated killing process. PKC inhibitors H-7 and staurosporine markedly suppressed the killing of S. aureus by monocytes stimulated by cross-linking Fc gamma RI or -II. Cross-linking Fc gamma R caused a transient increase in PKC activity in the membranes of monocytes, as measured by Ca2+/phospholipid-dependent phosphorylation of histone. Western blot analysis revealed that cross-linking Fc gamma R stimulated a transient increase in PKC-beta in the membranes of monocytes with kinetics that correlated closely with the translocation of PKC activity. Cross-linking Fc gamma R on monocytes also stimulated the translocation of PKC-epsilon but not PKC-alpha. PMA and 1-oleoyl-2-acetylglycerol (OAG), which caused translocation of PKC-alpha, -beta, and -epsilon, did not stimulate the killing process. Incubation with these PKC activators for 10 min rendered monocytes unresponsive to stimulation of killing of S. aureus via Fc gamma R. It could be that activation of certain PKC isozymes, probably PKC-alpha and -epsilon, by these activators causes feedback inhibition of PLC and, consequently, the killing in monocytes, because PMA blocks the Fc gamma R-mediated intracellular inositol(1,4,5)P3 formation and PKC translocation. Together, our results indicate that PKC isozymes play an important role in both stimulation and inhibition of the Fc gamma R-mediated intracellular killing of bacteria by monocytes.

Lymphocyte subsets in bronchoalveolar lavage fluid of children without bronchopulmonary disease

Bronchoalveolar lavage (BAL) is increasingly used in the pediatric age group. However, normal values for BAL fluid (BALF) constituents are lacking. As part of an investigation to define reference values in children, we studied lymphocyte surface markers of BALF in 28 children 3 to 16 yr of age without bronchopulmonary disease. All of them were undergoing elective surgery for nonpulmonary illnesses. BAL was performed under general anaesthesia with tracheal intubation. A flexible bronchoscope (Pentax 3.5 or 4.9 mm) was wedged into the middle lobe or into one of its segments, and 3 x 1 ml/kg body weight normal saline warmed to body temperature were instilled and immediately withdrawn. The first sample was studied separately; subsequent samples were pooled for analysis. Studies on lymphocyte surface markers were performed on the pooled sample only. The distribution of B-cells, pan T-cells, and CD57 positive cells was within the range reported for adult subjects. However, CD4/CD8 ratios were lower than in adults (0.7 +/- 0.4, mean +/- SD). This decrease in the CD4/CD8 ratio was caused by an increase in CD8 cells. Comparative analysis of blood and BALF lymphocytes in a subgroup of children showed that CD4/CD8 ratios in blood were within the normal range reported for this age group and significantly higher when compared with BALF. The lower CD4/CD8 ratios in normal children have to be considered in the interpretation of BALF in children with pulmonary diseases.

Effect of intracerebroventricular injection of somatostatin or GABA on pain threshold and contents of GABA or somatostatin in rat brain

AIM

To study the interactive influence of somatostatin (Som) and GABA in the brain and its relation to the pain modulation.

METHOD

Using radioimmunoassay, amino acid analyzer and measurement of pain threshold.

RESULTS

Som 10 micrograms i.c.v. increased the pain threshold (from 4.2 +/- 0.2 to 7.0 +/- 1.1 s) of the rat, but reduced the content of GABA from 2.3 +/- 0.3 to 1.6 +/- 0.4 mumol g-1 in hippocampus and from 2.4 +/- 0.4 to 1.5 +/- 0.2 mmol kg-1 in brain stem. After depletion of the Som in brain by i.c.v. cysteamine (Cys, 600 micrograms), the content of GABA in hippocampus and brain stem was also reduced without modification of the pain threshold. GABA 1500 micrograms i.c.v. had no effect on the pain threshold, however, caused a decrease of Som content from 55 +/- 4 to 37 +/- 5 ng g-1 in hippocampus and from 84 +/- 4 to 55 +/- 6 ng g-1 in brain stem, which was blocked by bicuculline (10 micrograms). After reduced of the GABA content in brain by subcutaneous injection of isoniazid (300 mg kg-1), Som content of the hippocampus and rain stem was markedly elevated.

CONCLUSION

Som and GABA inhibited each other, unrelated to their pain modulation.

MCML--Monte Carlo modeling of light transport in multi-layered tissues

A Monte Carlo model of steady-state light transport in multi-layered tissues (MCML) has been coded in ANSI Standard C; therefore, the program can be used on various computers. Dynamic data allocation is used for MCML, hence the number of tissue layers and grid elements of the grid system can be varied by users at run time. The coordinates of the simulated data for each grid element in the radial and angular directions are optimized. Some of the MCML computational results have been verified with those of other theories or other investigators. The program, including the source code, has been in the public domain since 1992.

Microsatellite DNA and isozyme variability in a west African population of Anopheles gambiae

Microsatellites are defined as tracts of tandemly repeated short DNA sequences. Polymorphisms in this class of DNA are currently being used to generate a genetic map of the mosquito Anopheles gambiae. In the present study we explore the potential of microsatellites as a tool for studying the genetic structure of natural populations of this malaria vector. Genetic polymorphism at twenty enzyme coding gene loci and eleven microsatellite DNA loci was surveyed in a population of An. gambiae from Mali, West Africa. All of the microsatellite loci surveyed were polymorphic, as compared to 40% of the isozyme loci. The mean heterozygosity for the isozyme loci was only 0.097 (+/- 0.0035), but for the microsatellite loci it was 0.732 (+/- 0.060). The pattern of variability was very different between isozymes and microsatellites. Typically, at an isozyme locus a single allele occurred at a frequency > or = 0.75, whereas at microsatellite loci the most common allele had a frequency < 0.50. We conclude that microsatellites provide a rich source of genetic polymorphisms for the study of the population genetics of An. gambiae and are in many ways superior to isozymes for this purpose. We discuss the potential for utilizing genetically mapped microsatellite loci to explore the effect of chromosomal inversions on the distribution of genetic polymorphisms in An. gambiae.

[A study on expression of epidermal growth factor receptor in pleomorphic adenoma of lacrimal gland]

Expression of epidermal growth factor (EGF) receptor was examined in 32 cases of pleomorphic adenoma of lacrimal gland by means of an immunohistochemical method. While normal lacrimal glands were all negative for the antigen, EGF receptor was positive in 10 pleomorphic adenomas and the positive staining was mainly limited in the tumor cells in trabecular or duct-like arrangement or squamous metaplastic epithelium. These data suggest that the expression of EGF receptor be significantly higher in pleomorphic adenoma than in normal lacrimal gland, and also suggest that EGF receptor be expressed in the neoplastic cells which are considered to be of duct origin.

[Experimental study on in vivo hematopoietic regulation of interleukin-6 gene therapy]

Interleukin-6 (IL-6), a pleiotropic cytokine, is involved in extensive immune regulation and hematopoietic regulation. We observed the effect of fibroblast mediated human IL-6 gene therapy on hematopoiesis. The platelet counts started to increase at day 4 after implantation of IL-6 highly secreting fibroblast cells and peaked at day 10 and lasted at high level for 22 days. The neutrophil counts were elevated after their implantation, but WBC did not show any remarkable increase. The CFU-GM and CFU-MK in bone marrow and spleen were also increased significantly. The results demonstrated that fibroblasts mediated human IL-6 gene therapy can significantly augment in vivo hematopoietic functions in bone marrow and spleen and elevate the number of nuetrophils and platelets. This study provides a new approach to treat thrombopenia and chemotherapy or radiotherapy-induced hematopoietic suppression.

Effects of the phospholipase-C inhibitor, U73122, on signaling and secretion in pituitary gonadotrophs

The effects of inhibition of phosphoinositide hydrolysis by U73122 [1-(6-[17 beta-3-methoxyestra-1,3,5- (10) triene-17-yl] amino/hexyl) 1H-pyrroledione] and neomycin on agonist-stimulated intracellular signaling and secretory responses were analyzed in cultured pituitary cells and alpha T3-1 gonadotrophs. GnRH (100 nM)- and endothelin-1 (ET-1; 100 nM)-induced inositol (1,4,5)-trisphosphate and diacylglycerol formation in normal cells and immortalized gonadotrophs were reduced by U73122 in a concentration-dependent manner, with IC50 values of about 2 microM and complete inhibition at 10 microM U73122. Neomycin also reduced GnRH- and ET-induced inositol phosphate production in both cell types. Agonist-induced intracellular Ca2+ responses were also inhibited in both cell types by U73122 and neomycin at the same concentrations that inhibited their inositol phosphate responses. In cultured pituitary cells, agonist-induced LH release was inhibited by U73122 and neomycin in a dose-dependent manner. In perifused pituitary cells, U73122 completely inhibited GnRH- and ET-1-induced LH release, but after 10 min caused a progressive and substantial increase in basal LH release. In static cultures, U73122 inhibited agonist-induced LH response at low concentrations (up to 3 microM), but stimulated LH release at higher concentrations due to direct activation of exocytosis by the compound. When added alone, U73122 caused a concentration-dependent increase in LH release with an EC50 of about 7 microM and a maximum response similar that that elicited by GnRH. The stimulatory action of U73122 on LH release was not reduced in the absence of extracellular Ca2+. In contrast to cultured pituitary cells, alpha T3-1 gonadotrophs showed only constitutive exocytosis that was not affected by either neomycin or U73122. These results demonstrate that GnRH and ET(A) receptors are coupled to the phosphoinositide/Ca2+ transduction system in pituitary gonadotrophs, and provide evidence for the dependence of agonist-regulated exocytosis on this signaling pathway. The ability of U73122 to stimulate LH release could reflect an additional action of the compound at late steps in the exocytic pathway.

Soluble CD14 is increased in bronchoalveolar lavage of active sarcoidosis and correlates with alveolar macrophage membrane-bound CD14

CD14 is a myeloid differentiation antigen which exists in a membrane-bound (55 kD) and a soluble (48 kD) form. This antigen is a receptor for lipopolysaccharide (LPS) structures and triggers the production of various cytokines. The aim of this study was to evaluate whether in active sarcoidosis, a disease with increased proportions of alveolar macrophages (AM) with CD14 expression in BAL fluid, the soluble form of CD14 (sCD14) is also increased. The sCD14 levels were measured in BAL fluid with an ELISA, and membrane-bound CD14 was determined by an immunoperoxidase assay, in active sarcoidosis (n = 13), inactive sarcoidosis (n = 9), idiopathic pulmonary fibrosis (IPF) (n = 6), and control subjects (n = 8). Higher concentrations of sCD14 were present in BAL fluid of patients with active sarcoidosis (58 +/- 34 ng/ml) than in those with inactive disease (13 +/- 10 ng/ml), patients with IPF (5 +/- 5 ng/ml), or control subjects (10 +/- 8% ng/ml) (p < 0.01). Similarly, the proportions of AM expressing membrane-bound CD14 were increased in active sarcoidosis (91 +/- 6%) compared with inactive sarcoidosis (82 +/- 6%), patients with IPF (76 +/- 13%), and control subjects (79 +/- 9%) (p < .05). In sarcoidosis, a significant correlation was found between the sCD14 concentration in BAL fluid and AM membrane expression of CD14 (r = 0.57, p < 0.01). We conclude that sCD14 is increased in BAL of active sarcoidosis suggesting a potential role for this substance as marker of activity and in the pathogenesis of pulmonary sarcoidosis.

Peptide transporter function and prolidase activities in Caco-2 cells: a lack of coordinated expression

Peptide transport and prolidase activities were measured to determine whether the expression of these two components of protein nutrition are coordinately regulated; i.e., whether an increase in the peptide transporter function will necessarily lead to a higher prolidase activity, or vice versa. The results indicated that peptide transporter function and prolidase activity respond differently to cell differentiation and feeding schedules. The results also indicated that peptide transport and prolidase activities were different in two Caco-2 cell "clones", with S-K cells transported peptides at higher rates but had lower total prolidase activities, when compared to ATCC cells. These results suggest that the expression of the peptide transporter function and prolidase activity is not coordinated. In addition, both the transporter and the prolidase activities affected the overall transport of Phe when given as the dipeptide Phe-Pro, supporting the notion that intestinal absorption of peptides is an essential component of amino acid absorption. In conclusion, the evidence suggests that the peptide transporter function and prolidase activity are not coordinately expressed by the human intestinal Caco-2 cells.

Autocrine feedback death and the regulation of mature T lymphocyte antigen responses

Antigen-induced T cell death is an important regulatory mechanism in the peripheral immune system. Evidence suggests that this process depends on T cell growth-inducing lymphokines such as IL-2 and occurs in proportion to the degree of T cell receptor occupancy. Strong T cell receptor stimulation leads to the synthesis of death molecules such as Fas ligand and tumor necrosis factor that cause T cell suicide. We propose that T cell death under these circumstances is the culmination of a feedback control mechanism termed propriocidal regulation or autocrine feedback death that regulates the expansion of specific T cell clones under conditions of high lymphokine and antigen load. In a quasi-stochastic system such as the antigen receptor repertoire, feedback information may be essential for the appropriate regulation of peripheral immune responses. Our understanding of this feedback mechanism affords a means to manipulate antigen-specific T cell death in vivo. The application of this approach to the therapy of T cell-medicated immunological diseases is discussed.

Comparison of the transport characteristics of D- and L-methionine in a human intestinal epithelial model (Caco-2) and in a perfused rat intestinal model

Absorption mechanisms of L- and D-methionine (MET) in an in vitro cultured human intestinal epithelial cell model (Caco-2) and an in situ perfused rat intestinal model were investigated to determine if the kinetic characteristics of absorption are comparable in these two popular absorption models. The results indicate that the transport of L- and D-MET were concentration-dependent in both model systems, and displayed comparable Km values. The Km value for L-MET is 1.34 mM in the Caco-2 model and 3.6 mM in the perfused rat intestinal model, while the Km value for D-MET is 1.79 mM in the Caco-2 model and 2.87 mM in the perfused rat intestinal model. Although the Jmax values were not comparable because of significant methodology differences, the Jmax values for L-MET were always higher than that for D-MET. In addition, transport of L- and D-MET across the Caco-2 cell monolayers were also inhibited by 10 mM Phe and Lys while MeAIB, Pro and Glu were generally ineffective. Similar results were also observed with these inhibitors in the perfused rat intestinal model with the exception that a combination of Pro and Glu stimulated the uptake of L-MET. In conclusion, the transport characteristics of L- and D-MET are comparable in both model systems.

Reduction of tomato polygalacturonase beta subunit expression affects pectin solubilization and degradation during fruit ripening

The developmental changes that accompany tomato fruit ripening include increased solubilization and depolymerization of pectins due to the action of polygalacturonase (PG). Two PG isoenzymes can be extracted from ripe fruit: PG2, which is a single catalytic PG polypeptide, and PG1, which is composed of PG2 tightly associated with a second noncatalytic protein, the beta subunit. Previous studies have correlated ripening-associated increases in pectin solubilization and depolymerization with the presence of extractable PG1 activity, prior to the appearance of PG2, suggesting a functional role for the beta subunit and PG1 in pectin metabolism. To assess the function of the beta subunit, we produced and characterized transgenic tomatoes constitutively expressing a beta subunit antisense gene. Fruit from antisense lines had greatly reduced levels of beta subunit mRNA and protein and accumulated < 1% of their total extractable PG activity in ripe fruit as PG1, as compared with 25% for wild type. Inhibition of beta subunit expression resulted in significantly elevated levels of EDTA-soluble polyuronides at all stages of fruit ripening and a significantly higher degree of depolymerization at later ripening stages. Decreased beta subunit protein and extractable PG1 enzyme activity and increased pectin solubility and depolymerization all cosegregated with the beta subunit antisense transgene in T2 progeny. These results indicate (1) that PG2 is responsible for pectin solubilization and depolymerization in vivo and (2) that the beta subunit protein is not required for PG2 activity in vivo but (3) does play a significant role in regulating pectin metabolism in wild-type fruit by limiting the extent of pectin solubilization and depolymerization that can occur during ripening. Whether this occurs by direct interaction of the beta subunit with PG2 or indirectly by interaction of the beta subunit with the pectic substrate remains to be determined.

Protein tyrosine kinase activity is essential for Fc gamma receptor-mediated intracellular killing of Staphylococcus aureus by human monocytes

Our previous study revealed that the intracellular killing of Staphylococcus aureus by human monocytes after cross-linking Fc gamma receptor I (Fc gamma RI) or Fc gamma RII is a phospholipase C (PLC)-dependent process. The aim of the present study was to investigate whether protein tyrosine kinase (PTK) activity plays a role in the Fc gamma R-mediated intracellular killing of bacteria and activation of PLC in these cells. The results showed that phagocytosis of bacteria by monocytes was not affected by the PTK inhibitors genistein and tyrphostin-47. The intracellular killing of S. aureus by monocytes after cross-linking Fc gamma RII or Fc gamma RII with anti-Fc gamma R monoclonal antibody and a bridging antibody or with human immunoglobulin G (IgG) was inhibited by these compounds in a dose-dependent fashion. The production of O2- by monocytes after stimulation with IgG or IgG-opsonized S. aureus was almost completely blocked by the PTK inhibitor. These results indicate that inhibition of PTK impairs the oxygen-dependent bactericidal mechanisms of monocytes. Genistein and tyrphostin-47, which do not affect the enzymatic activity of purified PLC, prevented activation of PLC after cross-linking Fc gamma RI or Fc gamma RII, measured as an increase in the intracellular inositol 1,4,5-trisphosphate concentration. Cross-linking Fc gamma RI or Fc gamma RII induced rapid tyrosine phosphorylation of several proteins in monocytes, one of which was identified as PLC-gamma 1, and the phosphorylation could be completely blocked by PTK inhibitors, leading to the conclusion that activation of PLC after cross-linking Fc gamma R in monocytes is regulated by PTK activity. Together, these results demonstrate that PTK activity is essential for the activation of PLC which is involved in the Fc gamma R-mediated intracellular killing of S. aureus by human monocytes.