Defective fluid secretion and NaCl absorption in the parotid glands of Na+/H+ exchanger-deficient mice

Multiple Na(+)/H(+) exchangers (NHEs) are expressed in salivary gland cells; however, their functions in the secretion of saliva by acinar cells and the subsequent modification of the ionic composition of this fluid by the ducts are unclear. Mice with targeted disruptions of the Nhe1, Nhe2, and Nhe3 genes were used to study the in vivo functions of these exchangers in parotid glands. Immunohistochemistry indicated that NHE1 was localized to the basolateral and NHE2 to apical membranes of both acinar and duct cells, whereas NHE3 was restricted to the apical region of duct cells. Na(+)/H(+) exchange was reduced more than 95% in acinar cells and greater than 80% in duct cells of NHE1-deficient mice (Nhe1(-/-)). Salivation in response to pilocarpine stimulation was reduced significantly in both Nhe1(-/-) and Nhe2(-/-) mice, particularly during prolonged stimulation, whereas the loss of NHE3 had no effect on secretion. Expression of Na(+)/K(+)/2Cl(-) cotransporter mRNA increased dramatically in Nhe1(-/-) parotid glands but not in those of Nhe2(-/-) or Nhe3(-/-) mice, suggesting that compensation occurs for the loss of NHE1. The sodium content, chloride activity and osmolality of saliva in Nhe2(-/-) or Nhe3(-/-) mice were comparable with those of wild-type mice. In contrast, Nhe1(-/-) mice displayed impaired NaCl absorption. These results suggest that in parotid duct cells apical NHE2 and NHE3 do not play a major role in Na(+) absorption. These results also demonstrate that basolateral NHE1 and apical NHE2 modulate saliva secretion in vivo, especially during sustained stimulation when secretion depends less on Na(+)/K(+)/2Cl(-) cotransporter activity.

The beta-lactamases and beta-lactam antibiotic susceptibility of Yersinia enterocolitica

One hundred and forty-five isolates of Yersinia enterocolitica of different serotypes and biotypes, including atypical biotypes, collected from various parts of the world, were examined for their susceptibility to beta-lactam antibiotics and expression of intracellular beta-lactamases. The reasons for the specificity of patterns of susceptibility to beta-lactams for each biotype or subtype of Y. enterocolitica were elucidated by examining their ss-lactamase activity. Whilst the biotypes and subtypes were uniformly susceptible to the newer beta-lactam antibiotics, the susceptibility pattern observed with other beta-lactams was specific to each biotype or subtype, because of the characteristics of beta-lactamase expression by strains within these groups. The susceptibility to these beta-lactam agents depended entirely on the extent of elaboration or the absence of one of the two beta-lactamases, enzyme A and enzyme B, found in the species. Detection of enzyme B by a disc diffusion test yielded inconsistent results, but detection of enzyme A by disc diffusion was highly reliable. This test clearly distinguished strains of biotype 2, serotype O:5,27 from those of biotype 2, serotype O:9 and biotype 3, serotypes O:1, 2a-3, O:3 and O:5.

Novel translocation of the BCL10 gene in a case of mucosa associated lymphoid tissue lymphoma

Interest has focused on a recently identified gene, BCL10, thought to play an important role in the genesis of extranodal, marginal zone (MALT) lymphomas. This gene belongs to a family containing caspase recruitment domains (CARD), that are involved in the apoptotic pathway. Translocations of the BCL10 gene to the immunoglobulin heavy chain locus at 14q32 have been described. We report herein a case of MALT lymphoma showing t(1; 2)(p22; p12). The translocation was shown to involve the BCL10 gene and the immunoglobulin kappa light chain locus by fluorescence in situ hybridization.

Developmental regulation and asymmetric expression of the gene encoding Cx43 gap junctions in the mouse limb bud

The Gja1 gene encoding the gap junction connexin 43 (Cx43) is dynamically regulated during limb morphogenesis. Transcript expression is found in many regions of the limb bud known to be important in regulating limb growth and patterning. In the newly emerged limb bud, Gja1 transcripts are first expressed in the ventrodistal margin of the ectoderm, and later transcript expression is localized to the apical ectodermal ridge (AER). Interestingly, transcript expression in the ventrodistal ectoderm is initiated left/right asymmetrically, with some strain backgrounds showing reverse sidedness in the fore vs. hindlimb buds. In legless, a mouse mutant exhibiting both limb and left/right patterning defects, Gja1 transcripts could not be detected in this region. However, in the i.v./i.v. embryo, a mutant with randomization of body situs the same pattern of Gja1 asymmetry was found in the limb ectoderm regardless of body situs. This suggests that Gja1 transcript expression is not directly linked to signaling pathways involved in specification of the left/right axis. In addition to transcript expression in the apical ectodermal ridge, Gja1 transcripts were also found at high levels in the ventral ectoderm. In the limb bud mesenchyme, Gja1 transcripts were distributed in a posterior distal gradient, coincident with tissue known to have polarizing activity. With limb outgrowth and the initiation of limb mesenchyme condensation. Gja1 transcripts were localized in the presumptive progress zone, and in the condensing mesenchyme. In more proximal regions of the limb where mesenchyme differentiation has been initiated, Gja1 transcripts were expressed only in the outer mesenchymal cells comprising the presumptive perichondrium. Further analysis of transgenic mice ectopically expressing Wnt-1 in the limb mesenchyme revealed alterations in the pattern of Gja1 transcript expression in conjunction with the perturbation of limb mesenchyme condensation and differentiation. Together, these findings indicate that Cx43 gap junctions may mediate cell-cell interactions important in cell signaling processes involved in limb growth and patterning.

Intraventricular insulin suppresses the acoustic startle response in rats

We and others have previously reported that the hormone insulin alters brain noradrenergic function at the synaptic and molecular levels. In the present study, we examined the in vivo effect of insulin (administered chronically via osmotic minipumps at a dose of 5 mU/day into the third cerebral ventricle) on the acoustic startle response. Rats receiving chronic intraventricular insulin had a significantly reduced startle response relative to vehicle-treated controls (i.e., 47 +/- 21% of baseline control startle response). Because our previous findings suggest that on an acute basis, insulin may enhance endogenous noradrenergic activity by inhibiting norepinephrine reuptake, we speculate here that the chronic effect of insulin is similar to that of the noradrenergic reuptake blocker, desipramine, which has been reported to decrease baseline startle performance.

Genetic modification of cultured skin substitutes by transduction of human keratinocytes and fibroblasts with platelet-derived growth factor-A

Gene therapy promises the potential for improved treatment of cutaneous wounds. This study evaluated whether genetically modified cultured skin substitutes can act as vehicles for gene therapy in an athymic mouse model of wound healing. Human keratinocytes and fibroblasts were genetically engineered by retroviral transduction to overexpress human platelet-derived growth factor-A chain. Three types of skin substitutes were prepared from collagen-glycosaminoglycan substrates populated with fibroblasts and keratinocytes: HF-/HK-, containing both unmodified fibroblasts and keratinocytes; HF-/HK+, containing unmodified fibroblasts and modified keratinocytes; and HF+/HK-, containing modified fibroblasts and unmodified keratinocytes. Skin substitutes were cultured for two weeks before grafting to full-thickness wounds on athymic mice. The modified skin substitutes secreted significantly elevated levels of platelet-derived growth factor throughout the culture period. Expression of retroviral platelet-derived growth factor-A mRNA was maintained after grafting to mice, and was detected in all HF-/HK+ grafts and one HF+/HK- graft at two weeks after surgery. Although no differences were seen between control and modified grafts, the results suggest that genetically modified cultured skin substitutes can be a feasible mechanism for cutaneous gene therapy. The cultured skin model used for these studies has advantages over other skin analogs containing only epidermal cells; because it contains both fibroblasts and keratinocytes, it therefore offers greater opportunities for genetic modification and potential modulation of wound healing.

Enhanced vascularization of cultured skin substitutes genetically modified to overexpress vascular endothelial growth factor

Cultured skin substitutes have been used as adjunctive therapies in the treatment of burns and chronic wounds, but they are limited by lack of a vascular plexus. This deficiency leads to greater time for vascularization compared with native skin autografts and contributes to graft failure. Genetic modification of cultured skin substitutes to enhance vascularization could hypothetically lead to improved wound healing. To address this hypothesis, human keratinocytes were genetically modified by transduction with a replication incompetent retrovirus to overexpress vascular endothelial growth factor, a specific and potent mitogen for endothelial cells. Cultured skin substitutes consisting of collagen-glycosaminoglycan substrates inoculated with human fibroblasts and either vascular endothelial growth factor-modified or control keratinocytes were prepared, and were cultured in vitro for 21 d. Northern blot analysis demonstrated enhanced expression of vascular endothelial growth factor mRNA in genetically modified keratinocytes and in cultured skin substitutes prepared with modified cells. Furthermore, the vascular endothelial growth factor-modified cultured skin substitutes secreted greatly elevated levels of vascular endothelial growth factor protein throughout the entire culture period. The bioactivity of vascular endothelial growth factor protein secreted by the genetically modified cultured skin substitutes was demonstrated using a microvascular endothelial cell growth assay. Vascular endothelial growth factor-modified and control cultured skin substitutes were grafted to full-thickness wounds on athymic mice, and elevated vascular endothelial growth factor mRNA expression was detected in the modified grafts for at least 2 wk after surgery. Vascular endothelial growth factor-modified grafts exhibited increased numbers of dermal blood vessels and decreased time to vascularization compared with controls. These results indicate that genetic modification of keratinocytes in cultured skin substitutes can lead to increased vascular endothelial growth factor expression, which could prospectively improve vascularization of cultured skin substitutes for wound healing applications.

Disrupting the establishment of polarizing activity by teratogen exposure

Between days 9.5 and 10, the forelimb buds of developing murine embryos progress from stage 1 which are just beginning to express shh and whose posterior mesoderm has only weak polarizing activity to stage 2 limbs with a distinguishable shh expression domain and full polarizing activity. We find that exposure on day 9.5 to teratogens that induce the loss of posterior skeletal elements disrupts the polarizing activity of the stage 2 postaxial mesoderm and polarizing activity is not subsequently restored. The ontogeny of expression of the mesodermal markers shh, ptc, bmp2, and hoxd-12 and 13, as well as the ectodermal markers wnt7a, fgf4, fgf8, cx43, and p21 occurred normally in day 9.5 teratogen-exposed limb buds. At stage 3, the treated limb apical ectodermal ridge usually possessed no detectable abnormalities, but with continued outgrowth postaxial deficiencies became evident. Recombining control, stage matched limb bud ectoderm with treated mesoderm prior to ZPA grafting restored the duplicating activity of treated ZPA tissue. We conclude that in addition to shh an early ectoderm-dependent signal is required for the establishment of the mouse ZPA and that this factor is dependent on the posterior ectoderm.

Targeted disruption of the Nhe1 gene prevents muscarinic agonist-induced up-regulation of Na(+)/H(+) exchange in mouse parotid acinar cells

The onset of salivary gland fluid secretion in response to muscarinic stimulation is accompanied by up-regulation of Na(+)/H(+) exchanger (NHE) activity. Although multiple NHE isoforms (NHE1, NHE2, and NHE3) have been identified in salivary glands, little is known about their specific function(s) in resting and secreting acinar cells. Mice with targeted disruptions of the Nhe1, Nhe2, and Nhe3 genes were used to investigate the contribution of these proteins to the stimulation-induced up-regulation of NHE activity in mouse parotid acinar cells. The lack of NHE1, but not NHE2 or NHE3, prevented intracellular pH recovery from an acid load in resting acinar cells, in acini stimulated to secrete with the muscarinic agonist carbachol, and in acini shrunken by hypertonic addition of sucrose. In HCO(3)(-)-containing solution, the rate of intracellular pH recovery from a muscarinic agonist-stimulated acid load was significantly inhibited in acinar cells from mice lacking NHE1, but not in cells from NHE2- or NHE3-deficient mice. These data demonstrate that NHE1 is the major regulator of intracellular pH in both resting and muscarinic agonist-stimulated acinar cells and suggest that up-regulation of NHE1 activity has an important role in modulating saliva production in vivo.

The detection of enzyme A of Yersinia enterocolitica by a disc diffusion method

Yersinia enterocolitica has been described as expressing two types of chromosomal beta-lactamase, the broad spectrum enzyme A and the inducible cephalosporinase enzyme B. Nevertheless, not all Y. enterocolitica strains express both enzyme A and enzyme B; Y. enterocolitica strains of the less commonly isolated biotype 2, serotype O:5 (27) lack the enzyme A. Also, no other members of the Enterobacteriaceae have been demonstrated to produce enzyme A. Detection of this enzyme could therefore be a useful laboratory tool in distinguishing common pathogenic strains of Y. enterocolitica from other Enterobacteriaceae. A simple test by disc diffusion on agar for the recognition of enzyme A expression in Y. enterocolitica was evaluated. The test was based on the resistance to ticarcillin conferred by enzyme A and the highly effective inhibition of this enzyme by clavulanic acid. A typical additional zone of inhibition between the zones of inhibition around a ticarcillin 75 micrograms disc and an amoxycillin/clavulanate 3 micrograms disc was indicative of the presence of enzyme A. By contrast, a large zone of inhibition around the ticarcillin disc without an additional zone of inhibition, reflected the absence of enzyme A.

Targeted disruption of the murine Nhe1 locus induces ataxia, growth retardation, and seizures

In most cells, the ubiquitously expressed Na+/H+ exchanger isoform 1 (NHE1) is thought to be a primary regulator of pH homeostasis, cell volume regulation, and the proliferative response to growth factor stimulation. To study the function of NHE1 during embryogenesis when these cellular processes are very active, we targeted the Nhe1 gene by replacing the sequence encoding transmembrane domains 6 and 7 with the neomycin resistance gene. NHE activity assays on isolated acinar cells indicated that the targeted allele is functionally null. Although the absence of NHE1 is compatible with embryogenesis, Nhe1 homozygous mutants (-/-) exhibit a decreased rate of postnatal growth that is first evident at 2 wk of age. At this time, Nhe1 -/- animals also begin to exhibit ataxia and epileptic-like seizures. Approximately 67% of the -/- mutants die before weaning. Postmortem examinations frequently revealed an accumulation of a waxy particulate material inside the ears, around the eyes and chin, and on the ventral surface of the paws. Histological analysis of adult tissues revealed a thickening of the lamina propria and a slightly atrophic glandular mucosa in the stomach.

A Gsalpha mutant designed to inhibit receptor signaling through Gs

Hormonal signals activate trimeric G proteins by substituting GTP for GDP bound to the G protein alpha subunit (Galpha), thereby generating two potential signaling molecules, Galpha-GTP and free Gbetagamma. The usefulness of dominant negative mutations for investigating Ras and other monomeric G proteins inspired us to create a functionally analogous dominant negative Galpha mutation. Here we describe a mutant alpha subunit designed to inhibit receptor-mediated hormonal activation of Gs, the stimulatory regulator of adenylyl cyclase. To construct this mutant, we introduced into the alpha subunit (alphas) of Gs three separate mutations chosen because they impair alphas function in complementary ways: the A366S mutant reduces affinity of alphas for binding GDP, whereas the G226A and E268A mutations impair the protein's ability to bind GTP and to assume an active conformation. The triple mutant robustly inhibits (by up to 80%) Gs-dependent hormonal stimulation of adenylyl cyclase in cultured cells. Inhibition is selective in that it does not affect cellular responses to expression of a constitutively active alphas mutant (alphas-R201C) or to agonists for receptors that activate Gq or Gi. This alphas triple mutant and cognate Galpha mutants should provide specific tools for dissection of G protein-mediated signals in cultured cells and transgenic animals.

Effects of third intracerebroventricular injections of corticotropin-releasing factor (CRF) on ethanol drinking and food intake

Corticotropin releasing factor (CRF), a neuropeptide secreted by hypothalamic and extrahypothalamic neurons, is thought to mediate stress-related behaviors. The tension reduction hypothesis suggests that ethanol drinking reduces stress; that drinking is reinforced by this reduced stress; and that the probability of drinking therefore subsequently increases. CRF also decrease food intake, and might decrease ethanol drinking similarly. We addressed these hypotheses directly by assessing the effects of intracerebroventricular (i.c.v.) CRF upon ethanol drinking (1 h/day). Rats were provided drinking tubes containing ethanol solutions that were gradually incremented in concentration (from 2% to 8% w/v, over 38 days). Ethanol intakes remained stable, ranging from 0.4 to 0.5 g/kg per hour on average, and a two-bottle choice test revealed that ethanol was preferred reliably to water. Third-i.c.v. cannulae were surgically implanted and CRF or vehicle was acutely injected immediately prior to the sessions. CRF dose-dependently reduced ethanol intake by 31% (0.5 microg) and 64% (5.0 microg), and reduced 24-h food by 9% and 21%, respectively, but did not alter body weights. I.c.v. CRF reduced ethanol drinking despite any acute stress-like effects that may have been present. Hence, these data are inconsistent with the tension reduction hypothesis. On the other hand, our results support the concept that food intake and ethanol drinking may be mediated by similar mechanisms.

Effects of food deprivation on conditioned taste aversions in rats

Food deprivation increases the rewarding effects of self-administered drugs such as psychomotor stimulants and benzodiazepines. These drugs also possess aversive properties and can produce conditioned taste aversions (CTA). Because drug-seeking behavior is most likely affected by both the rewarding and aversive properties of drugs, we hypothesize that food deprivation might also attenuate a drug's aversive consequences. The CTAs induced by three different drugs (amphetamine, chlordiazepoxide, and LiCl) were assessed separately. Male Long-Evans rats were assigned to one of two feeding conditions: restricted (maintained at 80% of free-feeding body weight), or nonrestricted (with ad lib food). Both groups received CTA training, consisting of an intraoral infusion of a novel saccharin solution (10 min) followed immediately by one of two i.p. injections: paired rats received drug, and unpaired rats received a similar volume of saline. After 10 days of ad lib food access, saccharin was presented to all rats again, and the latency to reject the tastant was used as an index of CTA learning. The rats that had been food restricted at the time of conditioning exhibited attenuated CTAs relative to those that had not been deprived. These differences were seen only when a rewarding drug (amphetamine or chlordiazepoxide) and not when a nonrewarding drug (LiCl) was used as the unconditioned stimulus. In a separate experiment, we established that this effect is apparent only when the deprivation period precedes conditioning rather than precedes testing. The present results indicate that food deprivation modulates the acquisition of a CTA induced by amphetamine or chlordiazepoxide, but not LiCl.

The loss of ventral ectoderm identity correlates with the inability to form an AER in the legless hindlimb bud

We have characterized the early stages of murine hindlimb morphogenesis in the legless (lgl)mutant and non-mutant littermates. Initially the entire ventral ectoderm expresses many genetic markers characteristic of the AER (en-1, fgf-8, msx-2, dlx-2, cd44, and cx-43). Subsequently, the expression domain of most of these genes is restricted to the thickened ectoderm of the disto-ventral limb margin prior to forming an AER. In lgl, the expression of these genes is initiated but not maintained and the disto-ventral marginal ectoderm does not thicken. In contrast, Wnt7a expression is initiated and maintained in the dorsal ectoderm. The limb mesenchyme of lgl and non-mutant embryos initially expresses lmx-1b and fgf-10 uniformly. As the ventro-distal marginal ectoderm thickens, lmx-1b is progressively dorsally restricted in non-mutants but continues to be expressed ventrally in lgl hindlimb buds. These data suggest that establishment of a dorso-ventral ectodermal interface is not sufficient for AER formation and that restriction of lmx-1b to the dorsal mesenchyme is coordinately linked to AER formation.

Evidence for a common mutation in hereditary pancreatitis

Hereditary pancreatitis is an autosomal dominant disorder with incomplete penetrance. It is characterised by recurring episodes of severe abdominal pain and often presents in childhood. Recently, a mutation in the cationic trypsinogen gene was identified in this disease. Previously, only one mutation at residue 117 of the trypsinogen gene has been found in the five separate hereditary pancreatitis families, four from the USA and one from Italy. Alteration of the Arg117 site is believed to disrupt a fail-safe mechanism for the inactivation of trypsin, leading to autodigestion of the pancreas under certain conditions. Molecular analysis of the trypsinogen gene was carried out on a hereditary pancreatitis family from the UK. The same G to A mutation at residue 117 was identified in this family, suggesting that this is a common mutation in hereditary pancreatitis.

Exacerbation of acetazolamide teratogenesis by amiloride and its analogs active against Na+/H+ exchangers and Na+ channels

Postaxial forelimb ectrodactyly induced by acetazolamide given on Day 9.5 of murine gestation is thought to be mediated by reduced intracellular pH (pHi) within the limb bud. Coadministration of amiloride increases the incidence and severity of acetazolamide-induced forelimb malformations and further reduces limb bud pHi. These findings were hypothesized to be attributable to the action of amiloride as an inhibitor of Na+/H+ exchangers (NHEs), plasma membrane-localized proteins involved in the maintenance of cellular pH homeostasis. Here, we explored this hypothesis further by coadministering with acetazolamide, amiloride, or analogs known to preferentially inhibit NHEs 5-(N-methyl-N-isobutyl)-amiloride, 5-(N, N-hexamethylene)-amiloride, 5-(N, N-dimethyl)-amiloride, and 5-(N-ethyl-N-isopropyl)-amiloride or amiloride-sensitive Na+ channels (benzamil). The coadministration of either amiloride, benzamil, 5-(N, N-dimethyl)-amiloride, 5-(N-ethyl-N-isopropyl)-amiloride, or 5-(N-methyl-N-isobutyl)-amiloride all dose responsively increased the frequency and severity of forelimb malformations compared to acetazolamide alone. None of the analogs given alone induced forelimb ectrodactyly. The data are consistent with the original hypothesis that the exacerbation of acetazolamide teratogenesis is due to NHE inhibition. Surprisingly, benzamil was the most potent potentiator of acetazolamide teratogenesis. This result strongly suggests that amiloride-sensitive Na+ channels are also present within the murine embryo and are likely to play a role in pHi homeostasis.

Women's satisfaction with medical abortion with RU486

The combination of RU486 (mifepristone) and prostaglandin analogues has been used for medical abortion in several European centres. We surveyed 41 Australian women who successfully used this method of abortion in a World Health Organization-sponsored trial. Overall, the women were satisfied with the method and found the associated pain level acceptable.

Identification and characterization of the human homologue of SH3BP2, an SH3 binding domain protein within a common region of deletion at 4p16.3 involved in bladder cancer

In a search for candidate tumor suppressor genes within a 30-kb common region of deletion previously identified in bladder cancer cell lines, we isolated a 2.4-kb cDNA clone comprising 13 exons that spanned approximately 16 kb of genomic DNA. Mutation analysis was carried out by single-strand conformation polymorphism analysis on DNA from 12 bladder carcinoma cell lines and 26 bladder tumors with LOH on chromosome 4p. Direct sequencing of the transcript in 4 bladder carcinoma cell lines with deletions in this region was also carried out. Two polymorphisms in exons 2 and 5 were identified, but no tumor-specific mutations were found. Sequence analysis identified a high degree of homology with the mouse sh3bp2 gene, which is abl-binding, suggesting that this gene is the human homologue. The predicted amino acid sequence of the putative gene product contains a Src homology 2 domain, a Src homology 3 binding domain, and a pleckstrin homology domain, suggesting a possible role in signal transduction. No evidence was found to indicate that SH3BP2 is the tumor suppressor gene at 4p16.3 involved in bladder cancer. However, this study has identified an interesting human gene that is a potential negative regulator of the abl oncogene.

OPTX 20/20 and Press-On Optics bifocal segments: an evaluation

BACKGROUND

OPTX 20/20 and Press-On Optics removable bifocal segments were evaluated in three areas: optical quality, effects on vision, and stability under simulated environmental conditions.

METHODS

To evaluate optical quality, sphere, cylinder, and spherical equivalent powers were measured in center and peripheral portions of 10 segments, with powers ranging from +1.00 to +2.50 D.

RESULTS

Twelve of 20 OPTX 20/20 segments and six of 20 Press-On Optics +1.00 and +1.50 D segments failed to pass ANSI Z80.1 standards because of unwanted cylinder powers. With regard to vision, +2.00 D OPTX 20/20 segments provided a 1 Snellen line advantage in near acuity, as compared with the Press-On Optics segments. contrast sensitivity for low- and mid-spatial frequencies was not significantly different for segments of the two types.

CONCLUSION

For higher powers, the optical characteristics of the OPTX 20/20 segments are better and provide better visual acuity. For lower powers, distortion and small amounts of unwanted cylinder reduce the optical quality of the OPTX 20/20 segments. Both segment types retained adhesion to CR-39 carriers equally well and should be satisfactory for their designated purposes of providing temporary and removable adds for occasional use.