Close Physical Contact Research Articles

Sociality in a bark-dwelling huntsman spider from Australia,Delena cancerides Walckenaer (Araneae: Sparassidae)

Social behavior is reported for the first time in a member of the family Sparassidae (Araneae), the Australian huntsman spiderDelena cancerides Walckenaer. Unlike any previously known social spider, this is a bark dwelling species and, thus, its sociality cannot have its basis on an aerial web, the structure that has been considered central to the evolution of sociality in other spider species. Colonies ofD. cancerides may comprise up to 300 individuals living in close physical contact under the exfoliating bark of deadAcacia, Callitris andCasuarina species. Specimens maintained in the laboratory feed communally and capture prey jointly. Although this intranest tolerance and communal feeding behavior is reminiscent of other highly social spiders,D. cancerides notably differs from these other species in the extreme aggression shown towards members of foreign colonies, its outbred population structure, and lack of sex ratio bias. We suggest that sociality in this species may have been facilitated by the presence of extended maternal care in the ancestral phylogenetic lineage, as suggested by the occurrence of such behavior in related nonsocial species, and that colonial living may have arisen as a consequence of the reduction and fragmentation ofDelena's habitat associated with the rise to dominance of the eucalypts. The apparent colony recognition observed may have evolved becauseDelena's hunting habits may require mechanisms to locate one's own colony after foraging expeditions and to exclude wandering outsiders from entering one's nest, in contrast to web-bound species that do not need to leave their nest to forage. How the observed outbreeding is accomplished in the face ofDelena's extreme intolerance to members of other nests, as well as how new colonies are formed, are issues that have yet to be investigated.

Opiate systems in mother and infant primates coordinate intimate contact during reunion.

In humans, and non-human primates, reunion following a separation results in a positive emotional state, and an increase in affiliative behaviors. To examine the role of opiate systems, in mothers and infants in mediating reunion behavior, morphine and naltrexone were administered after a brief separation. Infants administered morphine (0.1 mg/kg IM) showed a significant reduction in clinging and girning, a vocalization emitted during close physical contact. Naltrexone (5 mg/kg IM) had opposite effects. When administered to mothers, again morphine decreased and naltrexone increased clinging. Morphine administered to mothers had a more transient behavioral effect which could not be accounted for by lower morphine blood levels. These results demonstrate that during reunion, the amount of intimate contact between a mother and her infant is regulated by the reciprocal activation of their opiate systems. This activation of opiate systems may reinforce the infant's need for attachment and the mother's role in care giving.

Regulation of human B cell activation by follicular dendritic cell and T cell signals.

Follicular dendritic cells (FDC) represent a unique cell type (Nossal et al. 1968; Szakal and Hanna 1968) within the B cell follicles of the secondary lymphoid tissues. During T cell-dependent humoral immune responses, B cells undergo proliferation, somatic mutation, isotype switching, positive selection, and differentiation into memory B cells and plasma cells within the FDC networks (Berek 1992; Kosco and Gray 1992; Kroese et al. 1987; Liu et al. 1992; Maclennan 1994; Nossal 1992). The close physical contact between FDC and B cells that occurs when B cells undergo dramatic phenotypic and genetic changes suggests that FDC may be directly involved in all these events. Based on the histological observations depicted in Fig. 1, follicular B cell response can be divided into three distinct stages, in which different B cell events occur: 1. Exponential growth of germinal center precursor cells within the primary follicles. Germinal center reaction is initiated by the rapid proliferation of about three precursor cells Kroese et al. 1987; Liu et al. 1991; Jacob end Kelsoe 1992), giving rise to a germinal center containing about 1.4 x 104 cells after 4 days of immunization (Liu at al. 1991. 2.A A fully developed germinal center has e dark zone and a light zone. Centroblasts in the dark zone proliferate and mutate (Berek et al. 1991; Jacob et al. 1991; Koppers et al. 1993; McHeyzer-Williams et al. 1993). They give rise to non-proliferating cemrocytes in the light zone. The high-affinity centrocytes ore positively selected (Weiss et al. 1992) by antigens deposited on FIDC end differentiates 1o either memory B cells (MCHevzer-Wiumms et al. 199. 1; Schittek and Rajewsky 1992; Weiss and Rajewsky 1990) or plasma cells (Kosco et al. 1989. The low-affinity centrooytes which have failed to be selected die by apoptosio(Liu et al. 1989). 3. After 3-4 weeks of immunization, fully developed germinal 6entena are replaced by small follicular foci which consist of a few antigen-specific B blasts associated with immune complex networks (Liu et al. 18B1). These foci may represent the chronic stimulation of memory B cells, which are fundamental for the rnain1ainenoe of serum imrnunoglobulin (lg) level (Tew et al. 1980) and long-lived memory B cell clones (Gray and Smarvall 1988). KeywordsGerminal CenterCD40 LigandFollicular Dendritic CellDark ZoneLight ZoneThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Type of Day-Care Setting and Risk of Repeated Infections

As a direct result of demographic and sociologic changes, increasing numbers of children are attending day care in all industrialized countries. Unfortunately, the close physical contact among children in day care favors the transmission of infectious diseases. Previous studies have focused mainly on the risk of upper respiratory tract infection (URTI) and otitis media, which are reported to occur two to three times more frequently in children attending day care centers than in those cared for at home.1-7 Similarly day-care attendance has been found to be associated with an increased risk of lower respiratory tract infections (LRTI),8 gastroenteritis,9 as well as with the dissemination of infections caused by hepatitis A,10 cytomegalovirus,11 and H. influenzae type b.12 Despite convincing evidence for a higher risk of infection in day-care centers, most parents do not have an acceptable alternative to day care. It may be more useful, therefore, to identify the types of day-care structures associated with lower infectious risks. Family day care, in which several children are cared for in another family setting, offers a viable alternative to group day care, but previous studies have provided conflicting information on the risk of respiratory infections and otitis media in this setting. In four studies, the risks observed in family day care were very close to those of children who remained at home3-5,8; in two, they were intermediate between the risks at home and those in formal day-care centers6,7; while in two others, they were very close to those in day-care centers.13 These conflicting results can be explained by several factors including the lack of strict definitions for the different types of day-care settings and failure to control for the potentially important confounding differences in the number of children attending each type, the age range (from 2 to 60 months), and the time per week spent in the setting.

Direct recognition of mRNA stop signals by Escherichia coli polypeptide chain release factor two

The interaction between the translational stop signal and the polypeptide chain release factor protein (RF) within complexes of Escherichia coli ribosomes has been investigated by site-directed photochemical cross-linking experiments. Twelve mRNA analogues containing 4-thiouridine residues as part of stop signals were synthesized. Highly efficient cross-linking to RF-2 from 4-thiouridine (sU) residues of sUGAN-containing mRNAs was observed, and cross-linking from those of sUAAN was observed at a lower efficiency. This indicates that RF-2 is in close physical contact with the stop signal on the ribosome. The yield of the RF-2-mRNA cross-link depended on the identity of the fourth base for the sUGAN set of signals, suggesting that the fourth base of the stop signal affects the interaction between RF-2 and the stop codon. A region previously implicated as part of the decoding site of the small ribosomal subunit, 1385-1420 of the 16 S rRNA, was also cross-linked with these mRNAs. No new cross-links were obtained in the presence of the release factor. The data are consistent with models in which the RF has an anticodon-like domain that contacts the stop signal directly at or near the ribosomal site in which sense codons are decoded.

Downregulation of human platelet reactivity by neutrophils. Participation of lipoxygenase derivatives and adhesive proteins.

Unstimulated neutrophils inhibited activation and recruitment of thrombin- or collagen-stimulated platelets in an agonist-specific manner. This occurred under conditions of close physical cell-cell contact, although biochemical adhesion between the cells as mediated by P-selectin was not required. Moreover, in the presence of monoclonal P-selectin antibodies that blocked biochemical platelet-neutrophil adhesion, thrombin-stimulated platelets were more efficiently downregulated by neutrophils. This suggested a prothrombotic role for P-selectin under these circumstances. The neutrophil downregulatory effect on thrombin-stimulated platelets was amplified by lipoxygenase inhibition with 5,8,11,14-eicosatetraynoic acid. In contrast, the neutrophil inhibitory effect on platelets was markedly reduced by platelet-derived 12S-hydroxy-5,8-cis, 10-trans, 14-cis-eicosatetraenoic acid (12S-HETE), as well as by the platelet-neutrophil transcellular product, 12S,20-dihydroxy-5,8,10,14-eicosatetraenoic acid (12S,20-DiHETE), but not by another comparable metabolite, 5S,12S-dihydroxy-6-trans, 8-cis, 10-trans, 14-cis-eicosatetraenoic acid (5S,12S-DiHETE), or the neutrophil-derived hydroxy acid leukotriene B4. The neutrophil downregulatory effect on thrombin-induced platelet reactivity was enhanced by aspirin treatment. This may represent a novel action of aspirin as an inhibitor of platelet function. These results provide in vitro biochemical and functional evidence for the thromboregulatory role of neutrophils and emphasize the multicellular aspect of hemostasis and thrombosis.

Development of cell‐cell coupling among cells of the oligodendrocyte lineage

The development of functional gap-junctional communication was studied in cells of the oligodendrocyte lineage. The presence of cell-cell coupling was determined by the passage of current between cells using a double whole-cell patch-clamp system or by injecting the low molecular weight dye Lucifer yellow into individual cells via a patch pepette and observing the diffusion of the dye into adjacent cells. The developmental stage of the cells under study was determined using antibodies to specific surface markers (04, 01, and 010) that characterize cells of sequential maturity along the oligodendrocyte lineage (Kuhlmann-Krieg et al., 1988; Sommer and Schachner, 1981; 1982). Both stages of precursor cells of this lineage, O4+ and O4-, almost never showed dye or electrical coupling, even though they were in close physical contact with other cells. The O1-positive oligodendrocytes with simple morphology were also noncoupled, with only few exceptions. In contrast, more than 40 percent of more mature, O10-positive oligodendrocytes showed cell-cell coupling detectable with both dye and current injection. Thus, the formation of gap junctions between cells of the oligodendrocyte lineage does not occur with, but some time after, the commitment of the cell to becoming an oligodendrocyte.

Effects of immobilization on growth, morphology, and DNA content of the ciliated protozoonTetrahymena thermophila

Morphological and physiological properties of Tetrahymena thermophila immobilized by encapsulation in calcium-alginate hollow spheres were found to be substantially different from those of suspended cells. Immobilized T. thermophila reached lengths of 70-100 microns, whereas the average cell of suspension cultures was about 40 microns long. Suspended cells appeared typically pear-shaped while immobilized cells developed a proboscis-like anterior end. Contrary to suspended T. thermophila, encapsulated cells were functionally deficient in phagocytosis although developing an oral apparatus. The diameter of the macronucleus of immobilized cells was about two times larger than the macronucleus of suspended cells and contained twice as much DNA, while the DNA content of the micronucleus remained unchanged. High cell density fermentations of suspended cells indicated that the alterations observed in immobilized cells were not due to close physical contacts between the cells.

Effects of immobilization on growth, morphology, and DNA content of the ciliated protozoon Tetrahymena thermophila

Morphological and physiological properties of Tetrahymena thermophila immobilized by encapsulation in calcium-alginate hollow spheres were found to be substantially different from those of suspended cells. Immobilized T. thermophila reached lengths of 70–100 μm, whereas the average cell of suspension cultures was about 40 μm long. Suspended cells appeared typically pear-shaped while immobilized cells developed a proboscis-like anterior end. Contrary to suspended T. thermophila, encapsulated cells were functionally deficient in phagocytosis although developing an oral apparatus. The diameter of the macronucleus of immobilized cells was about two times larger than the macronucleus of suspended cells and contained twice as much DNA, while the DNA content of the micronucleus remained unchanged. High cell density fermentations of suspended cells indicated that the alterations observed in immobilized cells were not due to close physical contacts between the cells.

Transmission of hepatitis C: sexual, vertical or exclusively blood-borne?

Serum samples from eight pregnant women and their offspring were studied by nested polymerase chain reaction (PCR) for detection of hepatitis C virus (HCV) RNA to evaluate mother–to–child transmission of this virus. The mothers were all infected with human immunodeficiency virus (HIV); none showed symptoms of HCV infection. Anti–HCV antibodies were tested for by recombinant immunoblot assay. HCV viral sequences were found in five of the mothers and four of eight children, three of them at birth. Viremia was persistent in one infant who had chronic transaminase elevation and persistently remained anti–HCV–positive. The other three babies had intermittent viremia; all were asymptomatic and lost anti–HCV antibodies during follow–up. This loss of antibodies was also observed in PCR–negative infants. Thus, these results demonstrate transmission of HCV from mother to child by women coinfected with HCV and HIV. They indicate the usefulness of PCR for direct and early detection of HCV viremia in neonates. Body fluids from 14 patients with chronic hepatitis C were analyzed for the presence of hepatitis C viral RNA using the polymerase chain reaction. Nucleic acids were extracted from serum, saliva, and semen in guanidinium thiocyanate, subjected to reverse transcription, and then amplified by a double polymerase chain reaction technique using “nested” primers from the highly conserved 5′ noncoding region of the hepatitis C virus genome. Hepatitis C viral RNA was found in the serum of all patients in titers ranging between 10-1 and 10-3. The hepatitis C viral genome was not detected in any saliva or semen sample. These findings suggest that body fluids of patients with chronic hepatitis C are rarely, if ever, contaminated with the hepatitis C virus. This may help to explain the infrequent transmission of this disease by sexual or close physical contact.

7 - Cell adhesion in the stromal regulation of haemopoiesis

Haemopoiesis occurs in close physical contact with elements of the bone marrow stroma. This review examines some adhesion molecules which are expressed in haemopoietic environments. These molecules may act to maintain cell contact between haemopoietic progenitors and the cellular and extracellular matrix elements of the marrow stroma. A review is undertaken of several families of adhesion molecules and their ligands, including integrins, CD44, LEC-CAMs, CAMs and variant glycosylation patterns expressed by haemopoietic cells. Both CD44 and integrin receptors have been implicated in mediating important cellular interactions within the haemopoietic system and the significance of these and other molecules in haemopoiesis is discussed.

Absence of hepatitis C viral RNA from saliva and semen of patients with chronic hepatitis C

Body fluids from 14 patients with chronic hepatitis C were analyzed for the presence of hepatitis C viral RNA using the polymerase chain reaction. Nucleic acids were extracted from serum, saliva, and semen in guanidinium thiocyanate, subjected to reverse transcription, and then amplified by a double polymerase chain reaction technique using "nested" primers from the highly conserved 5' non-coding region of the hepatitis C virus genome. Hepatitis C viral RNA was found in the serum of all patients in titers ranging between 10(-1) and 10(-3). The hepatitis C viral genome was not detected in any saliva or semen sample. These findings suggest that body fluids of patients with chronic hepatitis C are rarely, if ever, contaminated with the hepatitis C virus. This may help to explain the infrequent transmission of this disease by sexual or close physical contact. (Gastroenterology 1992 Apr;102(4 Pt 1):1306-8)

Absence of hepatitis C viral RNA from saliva and semen of patients with chronic hepatitis C

Body fluids from 14 patients with chronic hepatitis C were analyzed for the presence of hepatitis C viral RNA using the polymerase chain reaction. Nucleic acids were extracted from serum, saliva, and semen in guanidinium thiocyanate, subjected to reverse transcription, and then amplified by a double polymerase chain reaction technique using “nested” primers from the highly conserved 5′ non-coding region of the hepatitis C virus genome. Hepatitis C viral RNA was found in the serum of all patients in titers ranging between 10−1 and 10−3. The hepatitis C viral genome was not detected in any saliva or semen sample. These findings suggest that body fluids of patients with chronic hepatitis C are rarely, if ever, contaminated with the hepatitis C virus. This may help to explain the infrequent transmission of this disease by sexual or close physical contact.

Crying as social behavior

Twenty mother-infant pairs were observed once a week for 7-hour periods when the infants were 2, 3, 4, and 5 weeks old. The occurrence of crying and its relationship to patterning of maternal behaviors was studied in two social contexts: while the mother was holding the infant and while she was not holding the infant. There were significant individual differences in the amount of crying in each of these contexts. The amount of crying in the two contexts was not correlated. Six variables describing forms of maternal attention throughout the 7-hour day were selected, and profiles were formed from measures of these variables. These profiles were found to vary systematically as a function of the amount of crying while the mother was holding the infant. In this context, only physical stimulation increased linearly with increased crying, whereas other forms of attention showed a U-shaped function in relation to increased crying. No relationship was found between crying while the mother was not holding the baby and patterns of interaction. We conclude that the structuring of a mother-infant relationship is reflected in the amount of crying that occurs while mother and infant are in close physical contact. The results also provide evidence that the social context for an infant's crying must be taken into account if the full adaptive value of crying is to be understood.

Support seeking and support giving within couples in an anxiety-provoking situation: The role of attachment styles.

This study examined how adult attachment styles moderate spontaneous behavior between dating couples when 1 member of the dyad is confronted with an anxiety-provoking situation. Eighty-three dating couples were unobtrusively videotaped for 5 min in a waiting room while the woman waited to participate in an activity known to provoke anxiety in most people. Independent observers then evaluated each partner's behavior on several dimensions. Results revealed that persons with more secure attachment styles behaved differently than persons with more avoidant styles in terms of physical contact, supportive comments, and efforts to seek and give emotional support. Findings are discussed in the context of theory and research on attachment. Recently, a growing number of researchers have begun to explore how different attachment styles influence what transpires within adult relationships (e.g., Collins & Read, 1990; Feeney & Noller, 1990; Hazan & Shaver, 1987; Levy & Davis, 1988; Simpson, 1990). Virtually all of this research has been guided by Bowlby's (1969,1973,1980) attachment theory. Bowlby sought to understand why infants forge strong emotional bonds to their primary caregivers and why they often exhibit pronounced anxiety and distress when they are separated from them. Adopting an evolutionary- ethological perspective, he argued that the specific sequence of behavioral and emotional reactions associated with separation—protest, despair, and detachment—might reflect the operation of an innate attachment system designed to promote close physical contact between vulnerable infants and their primary caregivers. By maintaining close proximity with their caregivers, infants would be more likely to survive, to reproduce, and ultimately to pass attachment and proximity-seeking propensities on to subsequent generations. Although the tendency to seek proximity seems to be universal in infants, its development and elaboration over time is sensitive to specific environmental conditions, especially transactions between the infant and his or her primary caregiver. Past empirical research has examined characteristic patterns of attachment behavior that develop between infants and their caregivers that signify different types of infant-caregiver relationships. Using the Strange Situation paradigm, Ainsworth, Blehar, Waters, and Wall (1978) identified three primary patterns

Production of antifungal metabolites by the ectomycorrhizal fungusPisolithus tinctorius strain SMF

An ectomycorrhizal fungus,Pisolithus tinctorius strain SMF, isolated from a basidiocarp removed from the roots of a recently fallen old growth fir in the Smoky Mountains of Tennessee, was characterized for its in vitro production of antifungal metabolites. On solid mediumP. tinctorius SMF strongly inhibited growth of strains ofFusarium solani, Geotrichum candidum, Phanerochaete chrysosporium, andVerticillium dahliae, all species known to be plant pathogens. Evidence from paired colony growth inhibition studies on agar plates indicated that production of antifungal agents byP. tinctorius SMF may be enhanced by close physical contact with other fungi. The antifungal activity ofP. tinctorius SMF was much greater than that of several culture collection strains ofP. tinctorius. The culture collection strains either showed no or very limited activity. The antifungal activity was associated with an apparently inducible metabolism ofP. tinctorius SMF and with the production of darkly colored water soluble phenolic metabolites. Small scale fermentation studies showed that the phenolics are readily producible by submerged culture fermentation. This is the first report of submerged culture production of antifungal metabolites by an ectomycorrhizal fungus.

Adhesion of human B cells to follicular dendritic cells involves both the lymphocyte function-associated antigen 1/intercellular adhesion molecule 1 and very late antigen 4/vascular cell adhesion molecule 1 pathways.

Presentation of antigen in the form of immune complexes to B lymphocytes by follicular dendritic cells (FDC) is considered to be a central step in the generation of memory B cells. During this process, which takes place in the microenvironment of the germinal center, B cells and FDC are in close physical contact. In the present study, we have explored the molecular basis of FDC-B cell interaction by using FDC and B cells derived from human tonsils. We found that FDC express high levels of the adhesion receptors intercellular adhesion molecule 1 (ICAM-1 [CD54]) and vascular cell adhesion molecule 1 (VCAM-1), while the B lymphocytes express lymphocyte function-associated antigen 1 (LFA-1 [CD11a/18]), very late antigen 4 (VLA-4 [CD49d], and CD44. Furthermore, we established that both the LFA-1/ICAM-1 and VLA-4/VCAM-1 adhesion pathways are involved in FDC-B lymphocyte binding, and therefore, these pathways might be essential in affinity selection of B cells and in the formation of B memory cells.

Codon recognition in polypeptide chain termination:site directed crosslinking of termination codon toEscherichia colirelease factor 2

An RNA synthesized in vitro was positioned on the Escherichia coli ribosome at the P site with tRNAala, and with a termination codon, UAA, as the next codon in the A site. Such a complex bound stoichiometric amounts of release factor 2 (RF-2); a corresponding RNA with UAC in place of UAA was not a template for the factor. An RNA containing 4-thio-UAA in place of the UAA supported binding of RF-2, and this has allowed site-directed crosslinking from the first position of the termination codon to answer two long standing questions about the termination of protein biosynthesis, the position of the termination codon and its proximity to the release factor during codon recognition. An RF-2.mRNA crosslinked product was detected, indicating the release factor and the termination codon are in close physical contact during the codon recognition event of termination. The 4-thio-U crosslinked also to the ribosome but only to the 30S subunit, and the proteins and the rRNA site concerned were identified. RF-2 decreased significantly the crosslinking to the ribosomal components, but no new crosslink sites were found. If the stop codon was deliberately displaced from the decoding site by one codon's length then a different pattern of crosslinking in particular to the rRNA resulted. These observations are consistent with a model of codon recognition by RF-2 at the decoding site, without a major shift in position of the codon.

CD4 and CD8 molecules can physically associate with the same T-cell receptor.

The expression of the cell-surface glycoproteins CD4 and CD8 on functionally mature T cells is usually mutually exclusive and correlates with class II and class I major histocompatibility complex (MHC) restriction, respectively. CD4 and CD8 function by binding to class II and class I MHC molecules on the antigen-presenting cell (APC), thereby increasing the adhesion between the T cell and the APC. From antibody-blocking studies and from cocapping and comodulation experiments, CD4 and CD8 come into close physical contact with their appropriately restricted T-cell receptor (TCR) at the time of antigen recognition. By the use of affinity chromatography followed by two-dimensional diagonal gel electrophoresis, we have identified a Mr 43,000 disulfide-bonded heterodimer copurifying with CD4. This protein was identified as the TCR by its removal after preclearing with the anti-TCR antibody F23.1 and by its generation after protease digestion of the same peptides as the TCR from this clone. When CD4 and CD8 were similarly isolated from an unusual CD4+ CD8+ class II-restricted T-cell clone, the TCR was identified as associating with either accessory molecule in the absence of activation. Therefore, CD4 and CD8 do not distinguish between class I- and class II-restricted TCRs in their ability to form membrane complexes, indicating a need for both the TCR and its associated accessory molecule to recognize the same individual MHC molecule on the APC to optimize TCR triggering.

Persistence of cytomegalovirus in mononuclear cells in peripheral blood from blood donors.

Human cytomegalovirus infection is common in the general population but generally remains silent; the risk of disease is greatest in fetuses and the newborn and in immunocompromised subjects. In addition to transmission of the virus by close physical contact iatrogenic infection occurs through blood transfusion and transplantation of organs.' Carriers of cytomegalovirus are normally identified from their antibody state, although the presence of virus can be detected by culture, assay for early antigens, or nucleic acid hybridisation. Most ofthese tests, however, are limited by their sensitivity or duration. The recent development of the polymerase chain reaction permits rapid and sensitive detection of viral genomes through specific amplification ofDNA or RNA sequences.2 We used the reaction to determine the incidence of cytomegalovirus DNA in mononuclear cells from blood donors.