Locus Heterogeneity for Waardenburg Syndrome is Predictive of Clinical Subtypes

Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between −2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3.     

Bringing the State Back In

Book reviewed in this article:
Culture and Society in New Order Indonesia . Virginia Matheson Hooker , ed. Kuala Lumpur: Oxford University Press, 1993. 302 pp. Dissociated Identities: Ethnicity, Religion, and Class in an Indonesian Society . Rita Smith Kipp. Ann Arbor: University of Michigan Press, 1993. 320 pp.     

The Receptor for Urokinase-Type Plasminogen Activator of a Human Keratinocyte Line (HaCaT)

It is assumed that plasmin participates in pericellular proteolysis in the epidermis. Plasmin is generated by keratinocyte-associated plasminogen activators from the proenzyme plasminogen; plasminogen activation can proceed at the keratinocyte surface. The resultant plasmin interferes with cell to matrix adhesion and does possibly contribute to keratinocyte migration during reepithelialization. Here we describe the receptor for urokinase-type plasminogen activator (uPA-R) in the human keratinocyte cell line HaCaT, which serves to direct plasminogen activation to the cell surface; we relate the receptor to the uPA-R previously described in human myclo-/monocytes. Binding of uPA to the receptor accelerated plasminogen activation by a factor of ≈10, compared to uPA in solution. Receptor-bound uPA was susceptible to inhibition by the plasminogen activator inhibitors 1 and 2. uPA and uPA-R antigen, as well as uPA activity, were localized to the leading front of expanding sheets of HaCaT cells. Exposure of HaCaT cells to plasminogen was followed by detachment of the cells. Detachment was prevented by an anti-catalytic anti-uPA antibody, by the plasmin-specific inhibitor aprotinin, and by the lysine analogue tranexamic acid, the latter of which prevents plasmin(ogen) binding to the cell surface. Our findings support the hypothesis that uPA-mediated plasminogen activation is characteristic of mobile rather than sessile keratinocytes. Moreover, the uPA-R seems to focalize plasminogen activation to the surface of cells at the site of keratinocyte migration.     

Response of tidal freshwater macrobenthos to sediment disturbance

The macrobenthic fauna in the tidal freshwater James River, Virginia, USA, exhibited a high degree of resilience and limited temporal response to sediment disturbance caused by large quantities of low bulk density (< 1.3 g cm^–3) fluid mud. The fluid mud was produced by hydraulic dredge deepening of a ship channel with disposal of dredged sediments onto a nearby shoal. The response of tidal freshwater communities to fluid mud was limited to mainly quantitative changes in abundance of dominant taxa (Limnodrilus spp., L. hoffmeisteri, Ilyodrilus templetoni, Corbicula fluminea, Coelotanypus scapularis) and was directly related to the thickness of fluid mud layers. Disturbance effects were short lived and for tubificids most obvious in areas with > 0.3 m fluid mud. In areas that received < 0.3 m fluid mud, acute effects were limited to chironomids and small (< 10 mm) C. fluminea. The fauna colonizing the areas disturbed by fluid mud was the same as that inhabiting the shoal prior to disturbance. There was no indication of a successional sequence, as reported for other freshwater and marine habitats. Three weeks after the disturbance ended, all but a few insect taxa had recolonized. Changes in community structure from fluid mud disturbance were slight with total taxa best characterizing the disturbance. The insensitivity of community structure measures reflects the high resiliency of macrobenthic communities to physical stresses in tidal freshwater systems.     

Sympathetic and sensory innervation of the urinary tract in young adult and aged rats: a semi-quantitative histochemical and immunohistochemical study

Summary The sympathetic innervation of the urinary tract of young adult (4 months) and aged (24+ months) rats has been examined by glyoxylic acid-induced fluorescence for the detection of noradrenaline and by immunofluorescence using antisera against tyrosine hydroxylase (TH) and neuropeptide Y (NPY). Immunostaining for calcitonin gene-related peptide (CGRP), known to be present in pelvic sensory nerves, was also performed. Semi-quantitative estimations of nerve densities were made of noradrenergic and peptidergic fibres innervating the smooth musculature of the ureter, bladder and urethra, and of the urinary tract vasculature. In the aged rats the overall patterns of innervation remained unchanged. However, with the exception of the vesical vasculature, the density of noradrenergic innervation decreased as did the intensity of histofluorescence. A similar pattern of results was observed by TH and NPY immunofluorescence. The results present evidence for a diminution in the sympathetic control of the urinary tract in aged rats. The pattern and density of CGRP-immunoreactive nerves was unchanged in the aged animals suggesting that pelvic visceral sensory innervation is more resistant to the effects of advancing age.     

Gonadal Steroid Hormone Receptors and Sex Differences in the Hypothalamo-Pituitary-Adrenal Axis

The rapid activation of stress-responsive neuroendocrine systems is a basic reaction of animals to perturbations in their environment. One well-established response is that of the hypothalamo-pituitary-adrenal (HPA) axis. In rats, corticosterone is the major adrenal steroid secreted and is released in direct response to adrenocorticotropin (ACTH) secreted from the anterior pituitary gland. ACTH in turn is regulated by the hypothalamic factor, corticotropin-releasing hormone. A sex difference exists in the response of the HPA axis to stress, with females reacting more robustly than males. It has been demonstrated that in both sexes, products of the HPA axis inhibit reproductive function. Conversely, the sex differences in HPA function are in part due to differences in the circulating gonadal steroid hormone milieu. It appears that testosterone can act to inhibit HPA function, whereas estrogen can enhance HPA function. One mechanism by which androgens and estrogens modulate stress responses is through the binding to their cognate receptors in the central nervous system. The distribution and regulation of androgen and estrogen receptors within the CNS suggest possible sites and mechanisms by which gonadal steroid hormones can influence stress responses. In the case of androgens, data suggest that the control of the hypothalamic paraventricular nucleus is mediated trans-synaptically. For estrogen, modulation of the HPA axis may be due to changes in glucocorticoid receptor-mediated negative feedback mechanisms. The results of a variety of studies suggest that gonadal steroid hormones, particularly testosterone, modulate HPA activity in an attempt to prevent the deleterious effects of HPA activation on reproductive function.     

The reductive acetyl coenzyme A pathway: sequence and heterologous expression of active methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase from Clostridium thermoaceticum.

The methyltransferase (MeTr) from Clostridium thermoaceticum transfers the N5-methyl group of (6S)-methyltetrahydrofolate to the cobalt center of a corrinoid/iron-sulfur protein in the acetyl coenzyme A pathway. MeTr was purified to homogeneity and shown to lack metals. The acsE gene encoding MeTr was sequenced and actively expressed in Escherichia coli at a level of 9% of cell protein. Regions in the sequence of MeTr and the E. coli cobalamin-dependent methionine synthase were found to share significant homology, suggesting that they may represent tetrahydrofolate-binding domains.     

Characterization of the interaction of the glp repressor of Escherichia coli K-12 with single and tandem glp operator variants.

The glp operons of Escherichia coli are negatively controlled by the glp repressor. Comparison of the repressor-binding affinities for consensus and altered consensus operators in vivo showed that all base substitutions at positions 3, 4, 5, and 8 from the center of the palindromic operator caused a striking decrease in repressor binding. Substitutions at other positions had a severe to no effect on repressor binding, depending on the base substitution. The results obtained indicate that the repressor binds with highest affinity to operators with the half-site WATKYTCGWW, where W is A or T, K is G or T, and Y is C or T. Strong cooperative binding of the repressor to tandem operators was demonstrated in vivo. Cooperativity was maximal when two 20-bp operators were directly repeated or when 2 bp separated the two operators. Cooperativity decreased with the deletion of 2 bp or the addition of 4 bp between the individual operators. Cooperativity was eliminated with a 6-bp insertion between the operators.     

TGF-β1 induces the expression of type I collagen and SPARC,and enhances contraction of collagen gels,by fibroblasts from young and aged donors

Fibroblasts have a major role in the synthesis and reorganization of extracellular matrix that occur during wound repair. An impaired biosynthetic or functional response of these cells to stimulation by growth factors might contribute to the delayed wound healing noted in aging. We, therefore, compared the responses of dermal fibroblasts from young and elderly individuals (26, 29, 65, 89, 90, and 92 years of age) to transforming growth factor-β1 (TGF-β1) with respect to: (1) the synthesis of type I collagen and SPARC (two extracellular matrix proteins that are highly expressed by dermal fibroblasts during the remodeling phase of wound repair) and (2) the contraction of collagen gels, an in vitro assay of wound contraction. With the exception of one young donor, all cultures exposed for 44 hours to 10 ng/ml TGF-β1 exhibited a 1.6- to 5.5-fold increase in the levels of secreted type 1 collagen and SPARC, relative to untreated cultures, and exhibited a 2.0- to 6.2-fold increase in the amounts of the corresponding mRNAs. Moreover, the dose-response to TGF-β1 (0.1–10 ng/ml), as determined by synthesis of type I collagen and SPARC mRNA, was as vigorous in cells from aged donors as in cells from a young donor. In assays of collagen gel contraction, fibroblasts from all donors were stimulated to a similar degree by 10 ng/ml TGF-β1. In conclusion, cells from both young and aged donors exhibited similar biosynthetic and contractile properties with exposure to TGF-β1. It therefore appears that the impaired wound healing noted in the aged does not result from a failure of their dermal fibroblasts to respond to this cytokine. © 1994 Wiley-Liss, Inc.     

Mitosis and cytokinesis in subconfluent endothelial cells exposed to increasing levels of shear stress

An in vitro flow apparatus in combination with cultured endothelium was used to determine the effects of fluid-generated shear stress on cells undergoing mitosis and cytokinesis. Cell responses were recorded by time-lapse video microscopy under phase contrast or Hoffman modulation contrast optics. Completion of cell division in mitotic cells was dependent upon both the initial presence of intercellular attachments and the magnitude of fluid wall shear stress. In nonisolated populations, 95.3%, 69.5%, and 57.1% of the cells completed cell division as opposed to 66.6%, 20.4%, and 11.9% in the isolated cell groups at 2.8, 14.1, and 33 dynes/cm², respectively. Prestressing cells for 14 h prior to monitoring failed to increase retention of isolated mitotic cells. The presence of neighboring cells facilitated replication by providing an anchoring attachment or a luminal surface for completion of division. Cell detachment most commonly occurred at the onset of cytokinesis when substrate contact areas were minimal and focal contacts were absent. A comparison between no flow controls and shear stress specimens indicated no significant differences in transit times for mitosis and cytokinesis. Thus, subconfluent endothelial cells may be more susceptible to detachment during cell division due to increases in shear stress, the absence of intercellular attachments, and reduced cell-substrate contacts. © 1994 wiley-Liss, Inc.