Cyclic AMP-dependent induction of serotonin N-acetyltransferase activity in photoreceptor-enriched chick retinal cell cultures: characterization and inhibition by dopamine

The activity of serotonin N-acetyltransferase (NAT), a key regulatory enzyme in the melatonin biosynthetic pathway, was examined in low-density monolayer cultures of chick embryo retinal cells prepared with three levels of photoreceptor enrichment. In cultures prepared from embryonic day 8 retinas (E8), photoreceptors represented approximately 30% of the total cell population, whereas in those prepared from embryonic day 6 retinas (E6), approximately 70% of the cells were photoreceptors. In E8 retinas treated with kainic acid to destroy neurons (E8K), the relative content of photoreceptors was increased to approximately 50%. NAT activity was detectable in the cultures under all conditions studied, and was markedly increased by drugs that increase intracellular cyclic AMP levels and cyclic AMP-dependent protein kinase activity: 8-bromocyclic AMP, forskolin, and 3-isobutyl-1-methylxanthine (IBMX). Consistent with the hypothesis that NAT is localized in photoreceptors, the effects of the stimulatory treatments were significantly greater in E6 and E8K cultures than in E8 cultures. The stimulation of NAT activity in E6 cultures was inhibited by actinomycin D and cycloheximide, suggesting the involvement of RNA and protein synthesis. Dopamine inhibited the induction of NAT activity by forskolin and IBMX, but not that elicited by 8-bromocyclic AMP. The dopamine-mediated suppression of activity was significantly inhibited by pertussis toxin and by spiperone and sulpiride, both D2-dopamine receptor antagonists, but not by SCH 23390, a D1-dopamine receptor blocker, or antagonists of alpha-adrenergic, beta-adrenergic, or serotonergic receptors. Because the inhibitory effect of dopamine on E6 and E8K cultures was at least as great as that on E8 cultures, the results suggest that dopamine acts on D2-like receptors on photoreceptors. The receptors appear to be coupled to adenylate cyclase through an inhibitory GTP-binding protein and to mediate inhibition of cyclic AMP synthesis and consequent induction of NAT activity.

The effect of anti-alpha-fetoprotein-adriamycin conjugate on a human hepatoma

Conjugates between chemotherapeutic agents and antibodies, linked by a dextran bridge, were previously shown to be effective in suppression of hepatoma growth in vitro and in vivo. However, scaling up of production of such conjugates may lead to a high degree of variation in molar ratios of drug to antibody in different batches. In this study, an alternative link between drug and antibody was evaluated. A conjugate between adriamycin and murine IgGI monoclonal antibodies to human alpha-fetoprotein was prepared using a polyglutamic-acid bridge. The simple and reproducible method of linking adriamycin to a specific site on the antibody enabled the binding of the drug to alpha-fetoprotein with a high yield (63% to 68%); the molar ratio of drug/antibody was in the range of 110:1 to 120:1. The conjugate retained its capacity to bind to purified alpha-fetoprotein. Incorporation of [3H]-thymidine or [3H]-leucine into hepatoma cells, which express alpha-fetoprotein, was inhibited by the conjugate, compared with unconjugated antibody. Furthermore, 90% of this pharmacological activity was preserved, compared with free adriamycin. In vitro, the inhibitory activity of the polyglutamic acid conjugate was higher than that of a conjugate in which dextran was used as the linker between drug and antibody. In vivo, both conjugates were equally effective in suppression of hepatoma growth transplanted subcutaneously in athymic mice. However, this effect lasted only during the treatment period of 2 to 3 wk. Six days after discontinuation of therapy, reacceleration of tumor growth was observed regardless of the conjugate used.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of transfected genes by differentiated, postmitotic neurons and photoreceptors in primary cell cultures

We report here that differentiated, primary, postmitotic neurons and photoreceptors in cultures obtained from embryonic chicks can express foreign genes after transfection by the calcium phosphate method. A variety of viral promoters were tested by using either beta-galactosidase or chloramphenicol acetyltransferase as reporter genes. Histochemical and immunocytochemical analysis showed beta-galactosidase expression by both neurons and photoreceptors. As commonly observed with dividing cells, transfection efficiencies showed inter-experimental variability, with efficiencies ranging from 2% to 20% using the same plasmid. On the other hand, intra-experimental variability between replicate dishes was much smaller. Analysis using the highly sensitive enzymatic assay for chloramphenicol acetyl transferase (CAT) showed that all of the promoter/enhancers-CAT constructs tested, with the exception of a construct containing the Maloney sarcoma virus promoter, led to the expression of detectable activity when transfected into cultured retinal cells. The calcium phosphate treatment used for cell transfection did not show detectable effects on overall cell survival, although it caused selective decreases in some metabolic activities of the cells. The studies demonstrate that it is possible to obtain expression of genes transfected into primary, postmitotic neuronal cells.

Mood changes, obstetric experience and alterations in plasma cortisol, beta-endorphin and corticotrophin releasing hormone during pregnancy and the puerperium

The relationships between mood change, obstetric experience and alterations in plasma cortisol, beta-endorphin (beta-EP) and corticotrophin-releasing hormone (CRH) were examined in a prospective study of 97 primiparous Australian women. Psychological measures were administered between the 28th week of pregnancy and the 3rd postnatal month, including the Profile of Mood States (POMS) and the Montgomery Asberg Depressive Rating Scale (MADRS). Blood samples were collected for cortisol, beta-EP and CRH assay on most of these occasions and during labour. Factor analysis was used to identify key subsets of psychological variables for use in the subsequent analyses. 'Mood disturbance' and 'tiredness' factors peaked at 38 weeks' gestation, while 'difficulty falling asleep' was greatest around the time of birth. Cortisol, beta-EP and CRH concentrations rose significantly as pregnancy advanced and peaked at birth; plasma CRH correlated with plasma cortisol (r = 0.54) and beta-EP (r = 0.32). Women with the highest 'mood disturbance' and MADRS depression scores at 28 weeks' gestation received significantly more pain relief during labour. Those women whose mood deteriorated from 38 weeks' gestation to postnatal day 2 had larger falls in plasma beta-EP after delivery (p less than 0.01) than those women whose mood improved or remained constant. Women in this mood-deteriorated subgroup also had significantly higher MADRS depression scores at 3 months (p less than 0.01). Mild antenatal depression (MADRS greater than 13) occurred in 5.2% of women and mild postnatal depression in 4.7%. Overall, these data suggest a role for circulating CRH in the regulation of maternal cortisol secretion and significant relationships between maternal postnatal mood states and beta-EP and between antenatal mood states and obstetric events.

Photoreceptor survival-promoting activity in interphotoreceptor matrix preparations: characterization and partial purification

It is well established that many types of cells are dependent on trophic factors for their survival. We are investigating whether photoreceptor survival may also be dependent upon such a factor, as well as the possibility that the interphotoreceptor matrix (IPM), which lies between the outer retina and the RPE, may be a source of photoreceptor survival-promoting activities. Well-characterized cultures of embryonic chick retinal neurons and photoreceptors, in which the photoreceptors spontaneously degenerate between 7 and 10 days in culture, were used to test this hypothesis. Crude extracts of IPM were found to support three- to fourfold increases in photoreceptor survival in 10-day cultures. This response was dose-dependent, saturable, and specific for photoreceptors, since there was no difference in the number of non-photoreceptor neurons between treated and control cultures. This photoreceptor survival-promoting activity (PSPA) may function when present either as a substratum-bound molecule or as a medium supplement. PSPA is heat labile, sensitive to freeze-thawing, and stable only within a very narrow pH range. The activity binds to heparin affinity columns but, in contrast to the behavior of growth factors such as FGF, it can be eluted from the columns at low salt concentrations (0.5 M NaCl). PSPA is eluted from a Sephacryl S-200 gel filtration column in two regions with Mr = 400-450 kDa and 33 kDa, respectively. SDS-gel electrophoresis suggests that the high molecular weight activity is composed of aggregates of lower molecular weight molecules. While this factor has not been purified to homogeneity, the combination of heparin-agarose affinity chromatography and hydrophobic interaction chromatography on phenyl-Sepharose columns results in 720-fold purification of the activity, with one unit of PSPA activity corresponding to 40 ng protein. This partial purification is accompanied by substantial reduction in the complexity of protein patterns in silver-stained SDS-gels. These findings are potentially important since a macromolecular factor promoting photoreceptor survival could play a role in the normal development of the retina, and could also further our understanding of retinal degenerations such as retinitis pigmentosa.

Synthesis and secretion of interphotoreceptor retinoid-binding protein (IRBP) by isolated normal and rd mouse retinal photoreceptor neurons in culture

Cultures of dissociated retinal neurons and photoreceptors from homozygous wild-type, heterozygous rd/+ and homozygous rd/rd retinas have been used to investigate the capacity of isolated photoreceptor cells to synthesize and secrete the interphotoreceptor retinoid-binding protein (IRBP). Retinal cells were dissociated on postnatal day 2 and grown in chemically defined medium in the absence of glial and pigmented epithelial cells. Expression of IRBP immunoreactive materials in these cultures was cell type-specific and developmentally regulated. Thus increasing numbers of rod photoreceptor cells showed immunoreactivity during the first week in culture, whereas nonphotoreceptor cell types remained consistently negative. Photoreceptor immunoreactivity could be detected in permeated (detergent-treated) as well as in unpermeated preparations, the latter suggesting that some IRBP is associated with the photoreceptor cell surface. These materials appeared to be loosely bound to the photoreceptors, since they disappeared when the cultures were exposed for 6 hr to IRBP-free medium but not when they were exposed to IRBP-containing medium. IRBP synthesis and secretion could be demonstrated by analyzing either cell extracts or conditioned medium by "slot blot" and Western blot techniques using affinity purified antibodies against bovine IRBP as well as by fluorographic analysis after metabolic labeling of the cultures with 35S-methionine. Comparisons of cultures from the different genotypes showed many similarities, including the abundance of IRBP-immunoreactive photoreceptors in 7 day cultures. However, immunochemical analysis showed lower conditioned medium/cell extract IRBP ratios in rd/rd cultures, an observation consistent with previous reports suggesting that IRBP secretion may be deficient in rd/rd photoreceptor cells.

Differential susceptibility of isolated mouse retinal neurons and photoreceptors to kainic acid toxicity. In vitro studies

Dissociated cultures of mouse retinal neurons and photoreceptors in chemically defined medium were used to investigate the susceptibility of these cells to the neurotoxin kainic acid (KA). Cells isolated from the newborn mouse retina were initially insensitive to this toxin, and the cells that differentiated as rod photoreceptors retained this resistance throughout the culture period. However, amacrine neurons became increasingly sensitive to KA toxicity as they differentiated in culture; after the fifth day in vitro approximately 90% of these cells were killed by KA in a concentration- and time-dependent fashion. The neurons showed pronounced swelling within 10 min of treatment onset, and cell lysis and nuclear fragmentation were evident during the next few hours. KA-induced degeneration of these neurons was corroborated using the amacrine cell-specific monoclonal antibody HPC-1, as well as autoradiographic and biochemical determinations of the high affinity uptake for GABA. This inhibitory neurotransmitter was taken up by amacrine neurons but not by photoreceptor cells, and this uptake was completely abolished in KA-treated cultures. Similar results were obtained with the neuronal enzyme choline acetyltransferase. However, both photoreceptor survival and the expression of photoreceptor markers such as opsin and the retinoid-binding protein interphotoreceptor (IRBP) were similar in KA-treated and control cultures. Similarly, the high affinity uptake of glutamate, an excitatory amino acid which is predominantly taken up by photoreceptors, showed only modest changes in KA-treated cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Na+,K+-adenosine triphosphatase polarity in retinal photoreceptors: a role for cytoskeletal attachments

We have used isolated embryonic photoreceptor cells as a model system with which to examine the mechanisms responsible for the development and maintenance of asymmetric Na+,K+-ATPase (ATPase) distribution. Photoreceptor precursors, which appear round and process free at culture onset, develop structural and molecular properties similar to those of photoreceptor cells in vivo. ATPase, recognized by an anti-ATPase antibody, is distributed over the entire surface of round photoreceptor precursors. As the cells develop, ATPase becomes progressively concentrated in the inner segment (where it is found in cells of the intact retina). This phenomenon occurs in cells developing in the absence of intercellular contacts. The development of ATPase polarity correlates with a decrease in the fraction of ATPase molecules that are mobile in the membrane (as determined by fluorescence photobleaching recovery), as well as with an increase in the fraction of ATPase that remains associated with the cells after detergent extraction. The magnitudes of the mobile ATPase fractions agree well with those of the detergent-extractable fractions in both the immature and developed photoreceptors. The distribution of alpha spectrin and ATPase-immunoreactive materials appeared qualitatively similar, and quantitative image analysis showed similar gradients of spectrin and Na+,K+-ATPase immunofluorescence along the long axis of elongated photoreceptors. Moreover, detergent extractability of alpha spectrin and the ATPase showed similar modifications in response to changes in pH or KCl concentration. ATPase detergent-extractable and mobile fractions were not changed in cultures treated with cytoskeletal inhibitors such as nocodazole. These data are consistent with a role for an asymmetrically distributed, spectrin-containing subcortical cytoskeleton in the preferential accumulation of Na+,K+-ATPase in the photoreceptor inner segment.

Characterization of transmitted motion in fetal lung: quantitative analysis

A simple two-dimensional analytic model is evaluated for transmitted cardiac motion in fetal lung. The model treats the latter as being an incompressible viscoelastic medium. The mean radial deformation in an elastic medium is demonstrated to depend on a length parameter l approximately square root of mu/rho omega 2, where mu, rho, and omega correspond to elastic shear modulus, mass density, and frequency of cardiac motion, respectively. Digitized M-mode images are demonstrated as a feasible method to measure such deformations in vivo. Data for two patients are presented to illustrate the technique.

Proteoglycan biosynthesis by chick embryo retina glial-like cells

In this report we present biochemical evidence that purified cultures of chick embryo retina glial-like cells actively synthesize heparan sulfate (HS) and chondroitin sulfate/dermatan sulfate (CS/DS) proteoglycans as well as hyaluronic acid. Glial-like cell cultures were metabolically labeled with [3H]glucosamine and 35SO4, and the medium, cell layer, and substratum-bound fractions were analyzed separately. Proteoglycans were characterized according to charge, apparent molecular size, and glycosaminoglycan (GAG) composition and were found to be differentially distributed among the cellular compartments. HS was the predominant GAG overall and was the major species found in the cell layer and substratum-bound fractions. CS/DS was also present in each fraction and comprised the largest proportion of GAGs in the medium. The major GAG-containing material resolved into three different size classes. The first, found in the cell layer and substratum-bound fractions, contained both CS/DS and HS and was of large size. A second, intermediately sized class with a higher CS/DS:HS ratio was found in the medium. The smallest class was found in the cell layer fraction and comprised HS, most likely present as free GAG chains. In addition, each fraction contained hyaluronic acid. Characteristics of these macromolecules differ from those produced by purified cultures of chick embryo retina neurons and photoreceptors in terms of size, compartmental distribution, and presence of hyaluronic acid.

Ganser syndrome in a 10 year old boy--an 8 year follow up

A case of pseudodementia in a 10 year old boy was first reported in 1981. When reviewed 8 years after initial presentation, his symptoms were largely unchanged. The case continues to be complicated by claims for compensation and a successful appeal against the initial compensation judgment.

Plasticity and differentiation of embryonic retinal cells after terminal mitosis

The relation between terminal mitosis and the events that determine the developmental fate of embryonic precursor cells is not well understood. This relation has now been investigated with [3H]thymidine autoradiography to determine the time of cell birth and with a culture system that allows the testing of the developmental potential of cells isolated from the chick embryo retina. Contrary to the situation in vivo, where neuronal differentiation always precedes photoreceptor differentiation, photoreceptor differentiation occurs prematurely and precedes neuronal differentiation when precursor cells are isolated from the retina at early embryonic stages. Thus, cells born by embryonic day 5 (ED-5) give rise predominantly to photoreceptors when isolated for culture on ED-6 but develop mainly as neurons when isolated on ED-8. This suggests that retinal precursor cells retain after terminal mitosis the capacity to develop either as neurons or as photoreceptors. Moreover, photoreceptor differentiation appears to represent a constitutive or "default" pathway that precursor cells follow in the absence of neuron-inducing signals.

Child behavior ratings: the influence of maternal characteristics and child temperament

This study investigated the extent to which maternal characteristics, such as psychological health problems, marital adjustment and confidence in mother/wife roles, influenced how mothers rated the behavior of their first-born children (n = 100) on the Pre-school Behavior Questionnaire. Results showed that these characteristics were powerful predictors of behavior ratings. In contrast, the independent contribution of child temperament ratings was relatively small. It was concluded that child behavior problem and temperament measures may be confounded. Maternal ratings constitute a valuable source of information concerning parent-child interaction which deserve further investigation, especially of their influence on generally accepted measures of child behavioral adjustment.

Opposing microtubule- and actin-dependent forces in the development and maintenance of structural polarity in retinal photoreceptors

We have used embryonic cells grown in vitro to study the roles of microtubules and microfilaments in the development and maintenance of the polarized shape of retinal photoreceptors. After several days in culture, isolated cone photoreceptors displayed a highly elongated, compartmentalized morphology similar to that of photoreceptors in vivo. When treated with the microtubule-depolymerizing agent nocodazole, these elongated photoreceptors became progressively shorter, eventually losing their compartmentalized structure and becoming round. Conversely, treatment with the actin-depolymerizing agent cytochalasin D caused the elongated photoreceptors to lengthen even further. Computer-assisted, quantitative analysis showed that responses of individual cells to both nocodazole and Cytochalasin D were concentration-dependent, graded, and reversible. Immunocytochemical studies suggested the presence of longitudinally oriented actin filaments and microtubules in these photoreceptors, prominent in the region that undergoes the most pronounced length changes in response to cytoskeletal inhibitors. Prior to becoming elongated, photoreceptor precursors could be accurately identified in early retinal cultures. These round cells undergo a stereotyped sequence of morphogenetic transformations during in vitro development, including elongation and compartmentalization of the cell body as well as extension of a single neurite. Treatment with either cytochalasin D or nocodazole completely blocked morphogenesis. In addition, cytochalasin D caused the development of an abnormal, elongated cell process, which formed by a microtubule-dependent mechanism. These nocodazole and cytochalasin D effects also were reversible. Taken together, these data indicate that the complex developmental transformations leading to photoreceptor polarization occur in the absence of intercellular contacts, and are predominantly controlled by intracellular cytoskeletal forces. They suggest the existence of continuously active, oppositely directed, microtubule- and actin-dependent forces, the balance of which is a determining factor in the development as well as the maintenance of the elongated, compartmentalized organization of photoreceptor cells.

Doxorubicin conjugates of monoclonal antibodies to hepatoma-associated antigens

A panel of six murine monoclonal antibodies against hepatocellular carcinoma-associated antigens, reactive with PLC/PRF/5 human hepatoma cells, was conjugated to Adriamycin (doxorubicin) via a dextran bridge. This library of antibodies includes three monoclonal antibodies against hepatitis B virus surface antigen, one anti-alpha-fetoprotein, and two other IgG2a antibodies against PLC/PRF/5 hepatoma-associated antigens. The use of dextran for conjugation of Adriamycin to antibodies enabled a 5- to 10-fold amplification of the number of drug molecules linked to antibody. Conjugation of Adriamycin to dextran caused an occasional reduction in the pharmacologic activity of dextran-Adriamycin in [3H]thymidine incorporation assays in hepatoma cells as compared to nonconjugated Adriamycin. This loss of anticellular activity was partially compensated for by conjugation of specific antibodies to the dextran-Adriamycin conjugate. Conjugated compounds completely retained their binding activity to purified hepatitis B virus surface antigen and alpha-fetoprotein fixed to a solid matrix as compared to binding of homologous nonconjugated antibodies. However, some reduction of the binding activity to intact hepatoma cells was observed in three of six conjugates. Binding activity to hepatoma cells and, as a consequence, suppression of tumor cell DNA synthesis by the various conjugates was enhanced as compared to the same effect in treated colorectal carcinoma cells that do not express the relevant hepatoma-associated proteins. Furthermore, two conjugates containing nonspecific antibodies did not bind to hepatoma cells and caused minimal suppression of DNA synthesis. These results suggest that this panel of monoclonal antibody-dextran-Adriamycin conjugates was effective in suppression of PLC/PRF/5 cell growth in vitro.

Induction of antioxidant enzyme activities by a phenylurea derivative, EDU

Oxygen free radicals have the potential to mediate cell injury. Defenses against such radicals include the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX). The purposes of this study were (1) to develop an in vitro model using human cells in which to investigate a potential pharmacologic agent as an inducer of these antioxidant enzymes; (2) to investigate the phenylurea derivative N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N-phenylurea (EDU) in this model with paraquat (PQ) serving as the positive control; and (3) to determine if induction of the antioxidant enzymes by EDU occurs in vivo. Human gingival fibroblasts (Gin-1) were used as the target cell in vitro; PQ and EDU, an inducer of SOD and CAT activities in plants, were evaluated as antioxidant enzyme inducers. Total SOD activity in Gin-1 cells increased 2-fold (p less than 0.05) in the presence of 1.0 mM PQ for 18-48 hr compared with untreated controls. Gin-1 cells incubated with 0.25-2.0 mM PQ for 24 hr had significantly increased total SOD (1.5 to 2.0-fold; p less than 0.05). CAT activity increased with 1.0 and 2.0 mM PQ (p less than 0.05). In the presence of PQ, GSH-PX activity decreased (p less than 0.05) in a concentration-dependent manner, indicating inactivation of this enzyme. No toxicity, indicated by lactate dehydrogenase released into the incubation medium, was noted at PQ concentrations below 5.0 mM. In the presence of 0.125-2.0 mM EDU, total SOD activity in Gin-1 cells significantly increased (1.5 to 2.0-fold; p less than 0.05). CAT activity significantly increased in a dose-dependent manner (p less than 0.05), while GSH-PX activity remained constant following exposure to 0.125-2.0 mM EDU. Intraperitoneal administration of EDU to rats twice a day for 2 days at 100 mg/kg induced SOD activity in heart, liver, and lung compared to controls (p less than 0.05). CAT activity increased in the liver 56% and in the lung 36% (p less than 0.05). GSH-PX activity remained constant. Our findings indicate that Gin-1 cells are a useful model in which to study inducers of antioxidant enzymes in vitro and that the phenylurea compound EDU induces SOD and CAT activities both in vitro and in vivo.

Selective failure of long-term survival of isolated photoreceptors from both homozygous and heterozygous rd (retinal degeneration) mice

Retinas from homozygous rdle/rdle and heterozygous rdle/++ C57BL/6J mice were dissected and dissociated on postnatal day 2, when they are still essentially indistinguishable. The resulting cell suspensions were seeded on highly adhesive substrata, to which the cells attach as individual units, and grown in vitro for 2 weeks in serum-free, chemically defined media. The behavior of neurons and photoreceptors in vitro was investigated with several techniques; essentially no differences were found between rdle/rdle and rdle/++ cells. Three distinctive cell types could be recognized in cultures of both genotypes towards the end of the first week in vitro: process-free cells, multipolar neurons and rod photoreceptors. There were similarities between rdle/rdle and rdle/++ cultures in the number and morphology of photoreceptor cells, to include the presence of a cilium and a short neurite terminating in a spherule-like body. Moreover, in cultures of both genotypes, only photoreceptors showed opsin immunoreactivity and the antigen recognized by the rod-specific monoclonal antibody RET-P1. Biochemical and autoradiographic studies demonstrated that rdle/rdle and rdle/++ cells also showed similar uptakes of the putative amino acid neurotransmitters glutamate and aspartate (associated with most of the photoreceptors and only some neurons), and gamma-aminobutyric acid (associated with neurons but absent in photoreceptors). Thus, according to several parameters, the properties shown by photoreceptor cells were similar in rdle/rdle and rdle/++ cultures during the first week in vitro. Massive photoreceptor cell death was observed in both genotypes during the second week in vitro, coinciding with the time when photoreceptor degeneration occurs in vivo in rd/rd, but not in rd/+ retinas. Photoreceptor death in culture appeared to be specific, since approx. 80% of the non-photoreceptor neurons survived normally during the period when photoreceptor degeneration took place. Several reports from the literature suggest that the period around postnatal days 8-10 represents a critical stage for rd/rd photoreceptors, since they survive until this time but degenerate thereafter. Genetically normal photoreceptors apparently undergo a comparable crisis during maintenance in primary culture, suggesting the involvement of cell-cell contacts and/or retina-derived environmental signals in the survival or rod visual cells.

Psychological and social adjustment of obese children and their families

The psychological and social adjustment of 30 obese children and their families was examined. Mothers completed the Child Behaviour Checklist and the Family Environment Scale; children completed the Self-Perception Profile for Children. The results consistently indicate that the obese children were less socially competent, had more behaviour problems, and had poorer self-perceptions than the non-obese normative samples. Families of obese children differed significantly from families in the non-distressed normative sample in that they interacted in a more negative way. The findings are discussed in terms of an 'at risk profile' and the implications for the behavioural treatment of obese children.

Development of neonatal mouse retinal neurons and photoreceptors in low density cell culture

We describe here a culture method which allows the growth of dissociated mouse retinal neurons and photoreceptors in chemically defined medium. Neural retinas from 2-day-old C57/BL mice were dissected from other ocular tissues, including the pigment epithelium, and dissociated into a cell suspension after brief trypsination. Most cells attached as single, unaggregated units to substrata pretreated with polyornithine and the neurite-promoting factor (PNPF). The cells were cultured in serum-free, high pyruvate Dulbecco's modified Eagle's medium containing chemically defined supplements. Under these conditions, onset of cell process development was rapid, giving rise to extensive neurite networks. Three morphologically distinct cell types were apparent during the first week in vitro. Some cells retained a circular outline and failed to produce processes, while 50-60% of the cells developed as multipolar neurons showing a large cell body and several neurites. Approximately 90% of these cells reacted with an amacrine cell-specific monoclonal antibody. Some 30% of the cultured cells expressed phenotypic properties characteristic of rod photoreceptors, including a small cell body, an apical cilium, a short neurite with a spherule-like terminal body, and immunoreactivity with antibodies against opsin as well as a rod cell-specific monoclonal antibody. No further signs of outer segment differentiation were observed in these cells. Non-neuronal "flat" cells, which represented less than 0.5% of the total cell number, reacted with an antibody against the glial fibrillary acidic protein. The number of neurons and photoreceptors remained relatively stable during the first 4-7 days in vitro. During the second week in culture, however, there was specific degeneration of greater than 90% of the photoreceptor cells, while less than 20% of the multipolar neurons were similarly affected. Consequently, in addition to providing a system for studying the differentiation of retinal neurons and photoreceptors, the specific degeneration of photoreceptors in these mouse retinal cell cultures makes this system ideal for investigating factors influencing photoreceptor survival.

Proteoglycan synthesis in flat cell-free cultures of chick embryo retinal neurons and photoreceptors

Extracellular matrix and cell surface proteoglycans are thought to play important roles in neural development and regeneration. Central nervous system proteoglycans have been isolated and characterized from rat and sheep brain and from chick neural retina. An experimental advantage offered by the latter tissue is that it is avascular and can be isolated free of connective tissue and pigment epithelium. Therefore, proteoglycans synthesized by this tissue are derived exclusively from neural cells. However, it has not yet been determined whether neurons and photoreceptors contribute to proteoglycan synthesis or whether these molecules are largely glial in origin. In the present study we have addressed this question using cultures of chick neural retinal cells free of flat, glial-like cells. Proteoglycans synthesized by cultures of retinal neurons, photoreceptors, and undifferentiated, process-free round cells from 8-day embryonic chick neural retina were metabolically labeled in vitro using [35S]sulfate and [3H]glucosamine as precursors. Radiolabeled proteoglycans accumulated in the medium, and could also be extracted from the cell layer by sequential treatments with Triton X-100 and with guanidine HCl. The proteoglycans were isolated by ion-exchange chromatography, and characterized by gel filtration chromatography and by susceptibility to degradation by enzymatic and chemical treatments. Overall, heparan sulfate proteoglycans were the predominant type of proteoglycan synthesized in vitro by the cultured neural retinal cells at this developmental stage. The medium and the Triton extract contained different proportions of both chondroitin sulfate and heparan sulfate proteoglycans, while heparan sulfate was the only proteoglycan recovered from the guanidine extract. These studies demonstrate that heparan sulfate and chondroitin sulfate proteoglycans are actively synthesized by cultures of neural retinal cells free of flat, glial-like cells.

Differential sensitivity of cultured retinal neurons and photoreceptors to herpes simplex infection

Infection of the retina with herpes simplex virus type 1 (HSV-1) causes devastating lesions usually leading to blindness. However, the interactions between individual retinal cell types and this virus have not been well characterized, probably because of limitations posed by the complexity of the intact retina. We have now approached this problem through the use of separate, purified populations of isolated chick embryo retinal neurons and photoreceptor cells, of glial cells, and of pigmented epithelial cells. This manuscript deals with the initial part of these studies, aimed at determining the susceptibility of different retinal types to HSV-1 infection. The different cultures were exposed to HSV-1 for 3-48 hr, and cell infection was evaluated by immunocytochemical detection of viral antigens or by autoradiographic study of viral DNA replication. Practically 100% of the retinal glial cells and pigmented epithelial cells appeared susceptible to HSV-1 infection. On the other hand, as many as 70% of the neurons present in glia-free, pigment epithelium-free cultures, also appeared infected after a 24-hr exposure to the virus. Neuronal susceptibility to HSV-1 was already present in early (2-day) cultures, was time- and concentration-dependent, and led to neuronal degeneration after 24-48 hr. Neuronal infection was also corroborated by the detection of viral particles by transmission electron microscopy. Photoreceptor cells were consistently and selectively resistant to HSV-1 infection at all the concentrations and time points investigated. Both immunocytochemical and autoradiographic studies showed similar results. Photoreceptor resistance to HSV-1 appears to be selective, since they could be readily infected with RNA viruses such as vesicular stomatitis virus and influenza virus. These cell culture preparations offer an attractive system for the investigation of cellular mechanisms involved in the differential susceptibility of retinal cells to viral infection. Moreover, they could also help in the screening of treatments potentially capable of preventing and (or) curing HSV-induced retinal infection.