Brief report: regression timing and associated features in MECP2 duplication syndrome

The aim of this study was to determine the frequency, timing, and associated features of developmental regression in MECP2 duplication syndrome. We also examined whether duplication size was associated with regression. Comprehensive psychological evaluations were used to assess 17 boys with MECP2 duplication syndrome. Information about regression was gathered via parent report. Eight of 17 boys exhibited regression in language skills, while seven of 17 exhibited regression in other skill areas. Regression in "other skill" areas coincided with seizure onset and with a prior autism diagnosis in six of seven participants. Regression was not associated with duplication size. Questions remain as to why some boys regress, and future work is necessary to understand the underlying mechanism(s) that causes regression.

Temporal and spatial expression of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) at the utero-placental interface during early pregnancy in the pig

AIMS

To determine the localisation and distribution of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) in uterine tissues from cycling and early pregnant pigs.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) or TGF-beta1 in uteri obtained from gilts on days 0, 5, 10, 12, 15, and 18 of the oestrous cycle or days 10, 12, 14, 16, 17, and 21 of gestation.

RESULTS

In cycling animals, CCN2 (CTGF) mRNA and protein were abundant in luminal epithelial cells (LECs) and glandular epithelial cells (GECs), with lesser amounts in stromal fibroblasts and little or none in endothelial cells. A similar pattern of staining was seen up to day 10 of pregnancy, except that overall staining intensities for CCN2 (CTGF) mRNA or protein were higher and that stromal and endothelial cells were CCN2 (CTGF) positive. However, on days 12-17 there was a striking decrease in the amount of CCN2 (CTGF) in LECs at the utero-conceptus interface, which was associated with maternal stromal matrix reorganisation and the onset of subepithelial neovascularisation. This differential distribution of CCN2 (CTGF) was localised to those LECs that were in close proximity to or in apposition with trophoblast cells. This decrease in CCN2 (CTGF) staining was transient in nature and high amounts of CCN2 (CTGF) were again apparent in LECs on days 17-21, when endometrial neovascularisation and matrix remodelling were complete. The expression of uterine TGF-beta1 was comparable to that of CCN2 (CTGF) at most stages of the oestrous cycle or early pregnancy. Pre-elongation blastocysts recovered on day 10 were positive for both CCN2 (CTGF) and TGF-beta1 in the extra-embryonic trophectoderm, endoderm, and inner cell mass. On day 12, trophectoderm expressed low amounts of TGF-beta1 mRNA and non-detectable amounts of TGF-beta1 protein or CCN2 (CTGF) mRNA or protein. By days 17-21, the expression of both growth factors in the extra-embyronic/placental membranes increased and frequently exceeded that seen in LECs.

CONCLUSIONS

The pattern of CCN2 (CTGF) production during the initial attachment phase supports a role for this factor in stromal remodelling and neovascularisation, although alternative functions at later stages such as epithelial-epithelial interactions are also possible. In most major cell types in the uterus or utero-placental unit, CCN2 (CTGF) expression was highly correlated with that of TGF-beta(1), indicating that CCN2 (CTGF) may mediate some of the functions of TGF-beta in the reproductive tract during the oestrous cycle and pregnancy. The data further highlight epithelium as an important source of CCN2 (CTGF) in the regulation of uterine function.

Steroidal regulation of connective tissue growth factor (CCN2; CTGF) synthesis in the mouse uterus

AIMS

To determine mechanisms regulating the production of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta1 (TGF-beta1) in the mouse uterus.

METHODS

In situ hybridisation and immunohistochemistry were used to localise CCN2 (CTGF) and TGF-beta1 in uteri from sexually mature female mice that had either been (1) mated with sterile males to induce pseudopregnancy or (2) ovariectomised (OVX) and administered estradiol-17beta (E2) or progesterone (P4), either alone or in combination. Uteri collected on days 0.5, 1.5, 2.5, 3.5, 4.5, or 5.5 of pseudopregnancy or at one, three, six, 12, or 24 hours after steroid administration were fixed, sectioned, and incubated with specific riboprobes or antibodies to permit detection and localisation of mRNA or protein for CTGF and TGF-beta1.

RESULTS

On days 0.5-2.5 of pseudopregnancy, CCN2 (CTGF) and TGF-beta1 were principally colocalised to uterine epithelial cells, with much smaller amounts in the stroma. On days 3.5-4.5, there was a reduction of CCN2 (CTGF) and TGF-beta1 in the epithelium but an increase in stromal and endothelial cells, corresponding to a period of extracellular matrix remodelling and neovascularisation within the endometrium. In OVX mice, epithelial cells were weakly positive for both CCN2 (CTGF) and TGF-beta1 in the absence of steroid hormones. Epithelial CTGF mRNA production were strongly but transiently stimulated in OVX mice cells by E2. These effects were antagonised by P4, which itself transiently stimulated epithelial CCN2 (CTGF) production, although less robustly than E2. CTGF and TGF-beta1 protein amounts were high in epithelial cells throughout steroid treatment and were increased in the stroma, where they were relatively long lived. Stromal CCN2 (CTGF) and TGF-beta1 were lower after co-administration of E2 and P4 than in response to each hormone individually. Although ccn2 (ctgf) is a TGF-beta1 inducible gene in other systems, and both growth factors were often co-localised in uterine tissues in these studies, several treatment regimens resulted in high amounts of TGF-beta1 protein in stromal cells without the concomitant production of ccn2 (ctgf) mRNA.

CONCLUSIONS

Maternal factors are principal cues for CCN2 (CTGF) and TGF-beta1 production in the uterus because (1) their expression during pseudopregnancy is comparable to that seen in pregnancy and (2) they are regulated by ovarian steroids. TGF-beta dependent and independent mechanisms of ccn2 (ctgf) gene transcription exist in the uterus that are variably regulated by steroid hormones. Collectively, the data support a role for CCN2 (CTGF) in mediating the effects of steroid hormones and TGF-beta on endometrial function.

The effect of diet on plasma homocysteine concentrations in healthy male subjects

OBJECTIVE

To determine the effect of habitual omnivorous and vegetarian diets on folate and vitamin B12 status and the subsequent effect on homocysteine concentration.

DESIGN

Cross-sectional comparison of free-living habitual meat-eaters and habitual vegetarians.

SETTING

The study was conducted at RMIT University, Melbourne.

SUBJECTS

One hundred and thirty-nine healthy male subjects (vegans n=18, ovolacto vegetarians n=43, moderate meat-eaters n=60 and high meat-eaters n=18) aged 20-55 y who were recruited in Melbourne.

OUTCOME MEASURES

Fasting plasma or serum from each subject was analysed for folate, vitamin B12 and homocysteine concentration. A semi-quantitative Food Frequency Questionnaire was completed by a subset of subjects from each group to determine methionine intake.

RESULTS

The two meat eating groups consumed significantly greater levels of methionine (P<0.001). There was no clear trend in plasma folate status between groups, however the plasma vitamin B12 concentration decreased progressively from the high-meat-eating group to vegans (P<0.05). An inverse trend was observed with plasma homocysteine concentration, with vegans showing the highest levels and high meat eaters the lowest (P<0.05).

CONCLUSIONS

Dietary methionine intake has no observable effect on plasma homocysteine concentration. In habitual diets, where folate intake is adequate, lowered vitamin B12 intake from animal foods leads to depleted plasma vitamin B12 concentration with a concomitant increase in homocysteine concentration. The suggested mechanism is the failure to transfer a methyl group from methyl tetrahydrofolate by vitamin B12 in the remethylation of homocysteine to methionine.

Nutrient intake and iron status of Australian male vegetarians

OBJECTIVE

The study was designed to investigate the iron intake and status of Australian, male vegetarians aged between 20 and 50 y.

DESIGN

Cross-sectional comparison of male vegetarians and age/sex matched omnivores.

SETTING

Free-living community subjects.

SUBJECTS

39 ovolactovegetarians, 10 vegans and 25 omnivores were recruited by local advertisement.

OUTCOME MEASURES

A 12-d semiquantitative dietary record to assess iron and zinc intake. Iron status was assessed by measurement of serum ferritin and haemoglobin concentrations.

RESULTS

Mean (s.d.) daily iron intakes of both the ovolactovegetarians (20.4 (7.7) mg/d) and vegans (22.9 (6.2) mg/d), were significantly higher than the omnivores' intake of 15.8 (4.5) mg/d. Ovo-lactovegetarians and vegans had significantly (P < 0.001 and P < 0.05, respectively) lower serum ferritin concentrations than omnivores: mean (s.d.): 64 (46.9), 65 (49.9) and 121 (72.5) ng/ml, respectively. Significantly more ovolactovegetarians and vegans than omnivores had serum ferritin concentrations below 25 ng/ml and below 12 ng/ml (P < 0.05). A higher proportion of omnivores had concentrations above 200 ng/ml (P < 0.05). The differences in serum ferritin concentrations between the vegetarians and omnivores remained significant even after exclusion of iron supplement users.

CONCLUSION

Australian male vegetarians had iron intakes higher than those of omnivores and above recommended levels, but their iron status was significantly lower.

Localization of connective tissue growth factor during the period of embryo implantation in the mouse

A role for connective tissue growth factor (CTGF) in reproductive function has been suggested from recent studies in the pig. To extend these findings, we have analyzed the immunohistochemical localization of CTGF during the estrous cycle and early pregnancy in mice. During the diestrous and early proestrous stages, CTGF was localized at high levels to both luminal and glandular uterine epithelial cells and at much lower levels in the stroma or myometrium. Epithelial expression of CTGF was considerably reduced at estrus. On Days 1.5-3.5 of pregnancy, CTGF was localized mainly to the uterine epithelial cells, which showed a substantially reduced level of CTGF on Day 4.5. On Days 5.5 and 6.5, CTGF was present at high levels in uterine decidual cells. CTGF was detected in the trophectoderm and inner cell mass of the preimplantation embryo on Day 4.5 and became preferentially localized to embryonic endoderm and mesoderm on Days 5.5-6.5. Multiple mass forms of CTGF (Mr 14 000-38 000) were present in endometrial extracts and uterine luminal flushings. Collectively, these data support a role for CTGF in uterine cell growth, migration, adhesion, and extracellular matrix production during the estrous cycle and early pregnancy, as well as in early development of the embryo.

Ovariectomy-induced changes in aged beagles: histomorphometry of rib cortical bone

Bone loss associated with estrogen depletion is well documented in cancellous bone but less well characterized in cortical bone. The effects of ovariectomy on the aged beagle skeleton were studied by histomorphometric analysis of the cortical bone in sequential rib biopsies. Biopsies were taken from each ovariectomized or sham-operated dog at the time of surgery and at 1, 4, and 8.5 months after surgery. Just prior to each postoperative biopsy, tetracycline, calcein, and xylenol orange, respectively, were administered by a fluorochrome labeling procedure (2d-10d-2d) to provide markers of bone formation. Analysis of sequential rib biopsies provided a means to follow the ovariectomy response over time and to compare each animal against its own baseline. Though ovariectomy did not influence histomorphometric indices at 1 month after surgery, a transient increase in cortical bone formation occurred thereafter, with a sixfold increase over that of sham-operated dogs at 4 months (P < 0.001) and a return to near control levels at 8.5 months. Cortical porosity increased by the fourth month after ovariectomy and remained high at 8.5 months. These data demonstrate for the first time that rib cortical bone is a responsive site for the effects of ovariectomy in aged female dogs.

Effects of cadmium on bone: an in vivo model for the early response

Cadmium (Cd) exposure induces bone resorption in vitro and in vivo that can lead to low bone mass and increased incidence of fracture. We have developed an animal model for following the early skeletal response to Cd. A low-calcium (but not calcium-deficient) diet is used to increase gastrointestinal absorption of calcium so that the endogenous fecal calcium excretion is essentially the total fecal calcium excretion. The bone response is followed by quantitation of stable fecal calcium and does not require a radioactive label. After mice were adjusted to a low-calcium diet, Cd was administered by a single gavage and fecal calcium was monitored to determine the magnitude of the calcium release from bone. Fecal calcium excretion (microg Ca/hr; mean +/- SE) remained at the background level for 8 hr (13.6 +/- 1.8, n = 18) but increased during the 8- to 24-hr and 24- to 56-hr collection periods (43.8 +/- 6.8, n = 12; 50.75 +/- 3.7, n = 6, respectively). The bone response was transient and dropped to nearly background levels during the 56- to 104-hr collection period. Blood calcium levels were normal throughout the time course. Bone resorption occurred at Cd levels of 7.9 +/- 0.7 microg/liter blood (mean +/- SE, n = 6), which is in the range of occupational exposure levels. The transient nature of the bone response contrasted to the slow but continuing rise observed in blood Cd levels. These results suggest that a threshold level of Cd is required for a bone response but that chronic levels of Cd in blood do not necessarily indicate the occurrence of continuous active bone resorption. This model can be used to probe early gene changes (prior to the bone response) that may be occurring in response to Cd exposure.

Effects of cadmium on osteoclast formation and activity in vitro

Chronic exposure to cadmium has been linked to bone loss, low bone mass, and increased incidence of fracture. To determine if Cd could directly increase the formation of cells responsible for bone resorption, we cultured normal canine bone marrow cells containing the progenitor cells for osteoclasts. Cultures were evaluated for the number of multinucleate osteoclast-like cells (MNOCs) formed. Exposure to Cd (10-100 nM) increased the number of MNOCs formed over control values when cultured in the presence but not in the absence of a bone wafer. The MNOCs formed were functional, evidenced by pits excavated on the bone wafers included in the cultures. By 12 days, MNOCs formed in the presence of 50 nM Cd excavated significantly more pits and a greater pit area than did untreated MNOCs. By 14 days, the control values were similar to those of the Cd-exposed MNOCs, but pit formation was enhanced by Cd in that the ratio of pit complexes to single pits was increased twofold over that for untreated cultures. Mature osteoclasts, isolated from the long bones of rat neonates and cultured for 1-3 days on bone slices, provided a direct method to assess the effect of Cd on osteoclast activity. Exposure of osteoclast cultures to 100 nM Cd increased the number of osteoclasts present over that for untreated osteoclasts by a factor of 1.7 +/- 0.1, the number of pits excavated by 2.8 +/- 0.6, the area excavated by 3.2 +/- 0.8, and the area excavated per osteoclast by 1.8 +/- 0.4 (mean +/- SE; n = six experiments). These data suggest that Cd accelerates the differentiation of new osteoclasts from their progenitor cells and activates or increases the activity of mature osteoclasts.

Parathyroid hormone (PTH)-PTH-related peptide hybrid peptides reveal functional interactions between the 1-14 and 15-34 domains of the ligand

Parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP) bind to a common PTH/PTHrP receptor. To explore structure-function relations in these ligands, we synthesized and functionally evaluated PTH-PTHrP hybrid peptides in which the homologous 1-14 portions were exchanged. Hybrid-2, PTH-(1-14)-PTHrP-(15-34)NH2, bound to LLC-PK1 cells expressing the cloned rat PTH/PTHrP receptor with high affinity (IC50 approximately equal to 7 nM). In contrast, hybrid-1, PTHrP-(1-14)-PTH-(15-34)NH2, bound with much weaker affinity (IC50 approximately equal to 8,700 nM). Thus, the 1-14 region of PTHrP is incompatible with the 15-34 region of PTH. The carboxyl-terminal incompatibility site was identified as residues 19-21 (Glu-Arg-Val in PTH and Arg-Arg-Arg in PTHrP); extending the amino-terminal PTHrP sequence to residue 21 but not to 18 cured the hybrid's binding defect. The amino-terminal incompatibility site was identified as position 5 (Ile in PTH and His in PTHrP), because Ile5-hybrid-1 bound with high affinity (IC50 approximately equal to 20 nM). The importance of these identified residues in the native ligands was established by evaluating the effects of substitutions at these sites in a series of PTH and PTHrP analog peptides. Overall, the results are consistent with the hypothesis that, in both PTH and PTHrP, the 1-14 and 15-34 domains interact when binding to the receptor and that residues 5, 19, and 21 contribute either directly or indirectly to this interaction.

The axr2-1 mutation of Arabidopsis thaliana is a gain-of-function mutation that disrupts an early step in auxin response

The dominant axr2-1 mutation of Arabidopsis thaliana confers resistance to the plant hormones auxin, ethylene, and abscisic acid. In addition, axr2-1 has pleiotropic effects on plant morphology which include gravitropic defects in roots, hypocotyls and inflorescences of axr2-1 plants. Two genetic screens were conducted to isolate new mutations at the AXR2 locus. First, axr2-1 pollen was gamma-irradiated, crossed onto wild-type plants, and the M1 progeny screened for loss of the axr2-1 phenotype. Large deletions of the axr2-1 region on chromosome 3 resulted; however, none of these deletions appeared to be heritable. In the second, M2 seed obtained from axr2-1 gl-1 plants was screened for reversion of the axr2-1 phenotype. One revertant line, axr2-r3, has a distinctive phenotype caused by a second mutation at the axr2 locus. To learn more about the nature of the axr2-1 mutation, the effects of varying the ratio of wild-type to mutant copies of the AXR2 gene were examined by comparing plants of the following genotypes: +/+, +/+/+, axr2-1/axr2-1, axr2-1/+ and axr2-1/+/+. Additionally, accumulation of transcripts from the auxin-inducible SAUR-AC1 gene was examined to determine the response of wild-type and mutant plants to auxin. Wild-type seedlings and mature plants accumulate transcripts with auxin treatment. In contrast, axr2-1 tissue does not accumulate SAUR-AC1 transcripts in response to auxin. Taken together, these results indicate that axr2-1 is a neomorphic or hypermorphic mutation that disrupts an early step in an auxin response pathway.

Determinants of [Arg2]PTH-(1-34) binding and signaling in the transmembrane region of the parathyroid hormone receptor

Previously, we reported that [Arg2]PTH-(1-34) bound to the rat osteosarcoma cell line, ROS 17/2.8, with 2-fold higher apparent affinity than it did to the opossum kidney cell line, OK, yet the analog was only a weak partial agonist for cAMP stimulation with ROS 17/2.8 cells, whereas it was a full cAMP agonist with OK cells. These results suggested that the rat and opossum PTH receptors differ in a region recognized by the hormone's amino-terminus. In this report we show that the cloned PTH receptors derived from ROS 17/2.8 and OK cells, expressed in COS-7 cells, also displayed altered responses to [Arg2]PTH-(1-34). Thus, [Arg2]PTH-(1-34) bound to the cloned rat PTH receptor with 7-fold higher affinity than it did to the cloned opossum PTH receptor, and in cAMP stimulation assays, it was a much weaker agonist with the rat receptor than it was with the opossum receptor. Studies with rat/opossum PTH receptor chimeras suggested that the membrane-spanning region of the receptor contributed to the different binding and signaling responses to [Arg2]PTH-(1-34). Point mutation analysis identified three sites in or near the extracellular ends of transmembrane domains V and VI, which specifically affected [Arg2]PTH-(1-34) binding and signaling.

Expressed emotion, perceived criticism, and relapse in depression: a replication in an Egyptian community

OBJECTIVE

The aims of this study were to determine the value of families' expressed emotion and patients' perception of family criticism in predicting relapse in Egyptian depressed patients and to evaluate transcultural differences in assessment of these measures.

METHOD

The subjects were 32 consecutive depressed patients from psychiatric clinics in Cairo and Ismailia, Egypt, who fulfilled the DSM-III-R criteria for major depression or bipolar disorder. An Arabic version of the Camberwell Family Interview was administered to key relatives of the depressed patients. Rating of expressed emotion was performed blindly by a qualified rater to assess levels of criticism, hostility, emotional overinvolvement, warmth, and positive remarks. Patient perception of family criticism (perceived criticism) was also assessed. All patients were followed up for 9 months to assess relapse and compliance with treatment.

RESULTS

The relation of family criticism to relapse was statistically significant. Although this result replicates previous findings, the criticism level that best differentiated relapsers and nonrelapsers was a score of 7, which is much higher than previously reported in Western studies. This relation was not observed for other expressed emotion components. Also, no association between perceived criticism and relapse was detected.

CONCLUSIONS

Expressed emotion is a prognostic factor that should be assessed with consideration of the specific culture and intrafamilial patterns. The use of perceived criticism in the prediction of relapse in depression is questionable. There is a need for a simplified, less time-consuming assessment tool that takes cross-cultural differences and specificities into consideration.

Gangrenous cholecystitis in an urban VA hospital

Gangrenous cholecystitis is an advanced form of acute cholecystitis associated with increased morbidity and mortality. We sought to determine the incidence of gangrenous cholecystitis in an urban VA hospital patient population and identify any distinguishing characteristics that may aid in its preoperative diagnosis. We retrospectively reviewed all urgent admissions that underwent cholecystectomy (n = 65) over the past 7 years at the Allen Park VAMC. Using histologic criteria, 17 (26%) of these patients had gangrenous cholecystitis. As a group compared to patients with nongangrenous cholecystitis, patients with gangrenous cholecystitis were statistically older (64 vs 54) and had an elevated WBC (15.4 vs 11.5) and increased serum glucose levels (203 vs 141). Preoperative imaging studies (ultrasound and cholescintigraphy) correctly identified only 31% of the gangrenous cholecystitis patients. We conclude that in an urban VA hospital patient population, the diagnosis of gangrenous cholecystitis cannot be accurately made or ruled out among urgent admissions with acute biliary disease. Considering the high incidence (26%) and difficulty confirming the diagnosis of gangrenous cholecystitis in this setting, we recommend early surgical intervention for this and similar patient populations.

Binding kinetics of ATP gamma S35 on cultured primary tracheal surface epithelial cells

Extracellular ATP can stimulate mucin release from primary hamster tracheal surface epithelial (HTSE) cells via a P2 purinoceptor-mediated mechanism, based on agonist potency studies of mucin release (Br. J. Pharmacol. 1991; 103:1053-1056). In the present study, we examined the kinetics of ATP binding to the surface of intact HTSE cells at 4 degrees C using ATP gamma S35 as a radioligand. We found that ATP gamma S35 bound to HTSE cells in a saturable, reversible manner, reaching an equilibrium at about 30 min. Scatchard analysis of equilibrium binding suggested the presence of two binding sites with Kd values of 0.47 and 9.4 microM. Competitive binding experiments, based on the ability of nucleotides and ATP analogs to block ATP gamma S35 revealed a rank order of ATP > ADP > alpha,beta-methylene ATP > 2-methylthio ATP > or = beta, gamma-methylene ATP. Neither AMP nor adenosine could inhibit the ATP gamma S35 binding. A comparison between the ability of nucleotides to compete with ATP gamma S35 binding and their ability to induce mucin release revealed a rather poor correlation (r2 = 0.67) with all of the above nucleotides but a good correlation (r2 = 0.96) without 2-methylthio ATP, indicating the presence of heterogenous ATP binding sites on the HTSE cell surface. UTP, a pyrimidine nucleotide, which is almost equipotent with ATP in its ability to stimulate mucin release, was much less potent than ATP in its ability to displace the ATP gamma S35 binding in these HTSE cells.

Analysis of parathyroid hormone's principal receptor-binding region by site-directed mutagenesis and analog design

Previous deletion studies established that the 25-34 region of PTH is important for receptor binding. We used oligonucleotide-directed mutagenesis to generate 47 different mutations in this region of human (h) PTH-(1-84) and evaluated cAMP-stimulating activity in ROS 17/2.8 cells. The hydrophobic residues Leu24 and Leu28 stood out as mutationally intolerant sites, while neighboring polar residues were comparatively tolerant. A series of synthetic PTH analogs was designed to test these residues further. The affinity of [Tyr34]hPTH-(1-34)NH2 for ROS 17/2.8 cells [dissociation constant (Kd), approximately 5 nM)] was dramatically reduced by the substitution of either Leu24 or Leu28 with Glu (Kd, approximately 20,000 and 8,000 nM, respectively). The Val31-->Glu substitution also sharply reduced affinity (Kd, approximately 200 nM). In contrast, the nearby charge-reversing change of Asp30-->Lys had no effect on binding affinity (Kd, approximately 5 nM). Similar effects were observed in the opposum kidney cell line. The binding of [Tyr34]hPTH-(15-34)NH2 to ROS 17/2.8 and opposum kidney cells (Kd, approximately 10 microM) was abolished by Glu substitutions at position 24, 28, or 31; the Lys30 change was without effect. These results suggest that the adverse effects of the Glu substitutions on receptor binding are not due purely to the disruption of tertiary interactions with the 1-14 region. Circular dichroism spectroscopy indicated that the substitutions do not affect local helical structure. The data suggest that Leu24, Leu28, and Val31 contribute important receptor-binding interactions and are consistent with the hypothesis that an amphipathic alpha-helix in the carboxy-terminal region of PTH-(1-34) is involved in receptor binding.

The roles of K5 and K14 head, tail, and R/K L L E G E domains in keratin filament assembly in vitro

Type I and type II keratins form obligatory heterodimers, which self-assemble into 10-nm intermediate filaments (IFs). Like all IF proteins, they have a central alpha-helical rod domain, flanked by nonhelical head and tail domains. The IF rod is more highly conserved than head and tail, and within the rod, the carboxy R/K L L E G E sequence is more highly conserved than most other regions. Mutagenesis studies have shed some light on the roles of the head, tail, and R/K L L E G E sequence in 10-nm filament structure. However, interpretations have often been complicated in part because many of these studies have focused on transfected cells, where filament structure cannot be evaluated. Of the few in vitro assembly studies thus far conducted, comparison of keratin mutants with other IF mutants have often been difficult, due to the obligatory heteropolymeric nature of keratin IFs. In this report, we describe in vitro filament assembly studies on headless, tailless, headless/tailless, and R/K L L E G E truncated mutants of keratin 5 and its partner keratin 14. Using varying conditions of ionic strength and pH, we examine effects of analogous K5 and K14 mutations on the stability of 10-nm filament structure. Using EM, we examine effects of mutations on the ability of subunits/protofibrils to (a) elongate and (b) laterally associate. Our results demonstrate that (a) tails of K5 and K14 are required for filament stabilization; (b) the head of K5, but not of K14, is required for filament elongation and lateral alignments; and (c) the R/K L L E G E domains are required for lateral alignments, but not for filament elongation.

Effects of the axr2 mutation of Arabidopsis on cell shape in hypocotyl and inflorescence

The axr2 mutation of Arabidopsis thaliana (L.) Heynh. confers resistance to the plant growth hormones auxin, ethylene and abscisic acid. In addition, mutant plants have a pronounced dwarf phenotype and display defects in both shoot and root gravitopism. To further characterize this mutant we have determined the phenotype of both dark- and light-grown mutant seedlings. We find that the height of axr2 hypocotyls is reduced in dark conditions compared with wild-type seedlings and that both dark- and light-grown hypocotyls have a gravitropic defect. In addition, we have examined the cellular anatomy of a variety of wild-type and axr2 tissues using light and scanning electron microscopy. Our results indicate that the axr2 mutation has a dramatic effect on cell length in both the inflorescence and the hypocotyl and a lesser effect on cell number in these tissues. The largest difference was observed in the epidermis of the inflorescence where axr2 cells were approximately eightfold shorter than wild-type cells. We suggest that these reductions in cell length and number are sufficient to explain most aspects of the axr2 phenotype. In addition, we propose that a reduction in auxin-mediated cell elongation is responsible for the gravitropic defect in mutant roots, hypocotyls and floral stems. Finally, we have found that the reduction in epidermal cell size in the mutant inflorescence is accompanied by a fourfold increase in stoma density. The implications of this result for models of stoma development are discussed.

Vasoactive intestinal polypeptide (VIP) inhibits rat alveolar macrophage phagocytosis and chemotaxis in vitro

Vasoactive intestinal polypeptide (VIP) has been shown to inhibit lymphocyte function and is believed to modulate the immune response. We explored the possible immunomodulatory effects of VIP on alveolar macrophage (AM) function by examining its influence on AM phagocytosis and chemotaxis. Rat AMs were collected by bronchoalveolar lavage and incubated for 90 min with polystyrene beads in the presence or absence of VIP in concentrations from 10(-11) M to 10(-5) M. VIP significantly (P less than 0.0001) inhibited AM phagocytosis of polystyrene beads at concentrations of 10(-11) to 10(-6) M, with a maximal inhibition of 35% at 10(-6) M (but no inhibition at 10(-5) M). AMs were also incubated for 90 min in a chemotaxis chamber with endotoxin-activated rat serum (EARS) as a chemoattractant, with or without VIP in concentrations from 10(-9) to 10(-6) M. VIP significantly (P less than 0.0001) inhibited AM chemotaxis by at least 30% at concentrations of 10(-9) to 10(-6) M, with a maximal inhibition of 46% at 10(-7) M. These results indicate that VIP, in concentrations from 10(-11) to 10(-6) M, inhibits rat AM function as assessed by phagocytosis of polystyrene beads and chemotaxis to EARS. The inhibition of alveolar macrophage function is another mechanism by which VIP may modulate the immune response in the lung.

The role of myosin I and II in cell motility

It has been recognized since the turn of the century that cell motility by non-muscle cells requires virtually continuous restructuring of the cytoskeleton (see refs [1-4]). It is also clear that cell motility requires a mechanism for converting chemical energy into mechanical work. The proteins actin and myosin, two important constituents of the cytoskeleton, have been postulated to act as the chemicomechanical transducer in motile cells. Central to their role as a force generating mechanism in motile cells is the ability of myosin (a) to hydrolyze ATP when it interacts with actin and (b) to form filaments. Recent studies on mammalian cells and on the cellular slime mold Dictyostelium discoideum have shed light and at the same time raised questions regarding the involvement of myosin in cell motility. Moreover, they have demonstrated the presence of two types of myosins, called myosin II and myosin I, that have unique biochemical and regulatory properties and that may play different roles in mediating cell motility. In this chapter we will discuss the properties of these two myosins and then describe what is known about their involvement in Dictyostelium and mammalian cell motility.

An increase or a decrease in myosin II phosphorylation inhibits macrophage motility

Myosin II purified from mammalian non-muscle cells is phosphorylated on the 20-kD light chain subunit (MLC20) by the Ca2+/calmodulin-dependent enzyme myosin light chain kinase (MLCK). The importance of MLC20 phosphorylation in regulating cell motility was investigated by introducing either antibodies to MLCK (MK-Ab) or a Ca2+/calmodulin-independent, constitutively active form of MLCK (MK-) into macrophages. The effects of these proteins on cell motility were then determined using a quantitative chemotaxis assay. Chemotaxis is significantly diminished in macrophages containing MK-Ab compared to macrophages containing control antibodies. Moreover, there is an inverse relationship between the number of cells that migrate and the amount of MK-Ab introduced into cells. Interestingly, there is also an inverse relationship between the number of cells that migrate and the amount of MK- introduced into cells. Other experiments demonstrated that MK-Ab decreased intracellular MLC20 phosphorylation while MK- increased MLC20 phosphorylation. MK- also increased the amount of myosin associated with the cytoskeleton. These data demonstrate that the regulation of MLCK is an important aspect of cell motility and suggest that MLC20 phosphorylation must be maintained within narrow limits during translational motility by mammalian cells.

Evaluation of the electroinjection method for introducing proteins into living cells

The introduction of impermeant probes such as antibodies and other proteins into living cells without compromising physiological function is an important approach for studying cellular regulatory mechanisms. Many techniques including direct microinjection, liposome-mediated delivery, fusion of red cell ghosts, and osmotic lysis of pinocytic vesicles have been used to introduce proteins into intact cells. We have used a modification of the voltage-discharge technique to introduce antibodies and other proteins into living physiologically responsive pheochromocytoma and other cultured cells. In this technique, called electroinjection, a single discharge of relatively low field strength is used to transiently permeabilize the plasma membrane. Our experiments demonstrate that electroinjection permits the introduction of large amounts (microM) of probe into 2-5 x 10(6) cells simultaneously without compromising cell viability or physiological responsiveness when performed under carefully defined conditions. They also demonstrate that electroinjection results in a single population of loaded cells and that protein incorporation is a function of field strength, capacitance, molecular weight of the protein, and the concentration of the protein in the electroinjection buffer. Interestingly, a significant fraction of the protein electroinjected into cells is trapped in the plasma membrane when cells are shocked at high capacitance. These results demonstrate that electroinjection appears to be an efficient method for loading exogenous proteins into cells while maintaining the integrity of the physiological properties of the cell.

Okadaic acid, a phosphatase inhibitor, decreases macrophage motility

Cellular locomotion results from a series of spatially and temporally integrated reactions. The coordinated regulation of these reactions requires sensitive intracellular signaling mechanisms. Because protein phosphorylation reactions represent important signaling mechanisms in mammalian cells, we investigated the effect of okadaic acid, a phosphoprotein phosphatase inhibitor, on protein phosphorylation and macrophage motility. Okadaic acid was applied to rat alveolar macrophages, and motility was quantitated by a directed chemotaxis assay. Okadaic acid inhibits macrophage motility in a dose-dependent fashion; the concentrations for 50 and 100% inhibition were 3 and 25 microM, respectively. Protein phosphorylation studies demonstrated a 2.5-fold increase in total protein phosphorylation in macrophages treated with 25 microM okadaic acid. These experiments also demonstrated a dose-dependent increase in the phosphorylation of the 20-kDa light chain of myosin. Moreover, 25 microM okadaic acid 1) maximally increased myosin light chain phosphorylation by 6.6-fold, 2) raised the level of myosin associated with the cytoskeleton from a basal level of 47.0 to 96.7% of the total myosin, and 3) induced profound morphological changes as visualized by scanning electron microscopy. These data correlate an increase in protein phosphorylation with a decrease in macrophage motility. Furthermore, they suggest that phosphoprotein phosphatase inhibition may prevent motility by uncoupling coordinated processes, such as cytoskeletal reorganization, that are essential for macrophage motility.

The aux1 Mutation of Arabidopsis Confers Both Auxin and Ethylene Resistance

Mutagenized populations of Arabidopsis thaliana seedlings were screened for plants capable of root growth on inhibitory concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. Four of the mutant lines recovered from this screen display a defect in root gravitropism as well as hormone resistance. The aerial portions of these plants are similar to wild-type in appearance. Genetic analysis of these four mutants demonstrated that hormone resistance segregated as a recessive trait and that all four mutations were alleles of the auxin-resistant mutation aux1 [Maher HP, Martindale SJB (1980) Biochem Genet 18: 1041-1053]. These new mutants have been designated aux1-7, 1-12, 1-15, and 1-19. The sensitivity of wild-type and aux1-7 roots to indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, and ethylene was determined. The results of these assays show that aux1-7 plants require a 12-fold (indole-3-acetic acid) or 18-fold (2,4-dichlorophenoxyacetic acid) higher concentration of auxin than wild-type for a 50% inhibition of root growth. In addition, ethylene inhibition of root growth in aux1-7 plants is approximately 30% that of wild-type at saturating ethylene concentrations. These results indicate that aux1 plants are resistant to both auxin and ethylene. We have also determined the effect of ethylene treatment on chlorophyll loss and peroxidase activity in the leaves of aux1 and wild-type plants. No difference between mutant and wild-type plants was observed in these experiments, indicating that hormone resistance in aux1 plants may be limited to root growth. Our studies suggest that the AUX1 gene may have a specific function in the hormonal regulation of gravitropism.

A dominant mutation in Arabidopsis confers resistance to auxin, ethylene and abscisic acid

We have screened a large population of M2 seeds of Arabidopsis thaliana for plants which are resistant to exogenously applied indole-acetic acid (IAA). One of the resistant lines identified in this screen carries a dominant mutation which we have named axr2. Linkage analysis indicates that the axr2 gene lies on chromosome 3. Plants carrying the axr2 mutation are severe dwarfs and display defects in growth orientation of both the shoot and root suggesting that the mutation affects some aspect of gravitropic growth. In addition, the roots of axr2 plants lack root hairs. Growth inhibition experiments indicate that the roots of axr2 plants are resistant to ethylene and abscisic acid as well as auxin.

Clearance of a persistent human enterovirus infection of the mouse central nervous system by the antiviral agent disoxaril

Enteroviruses can cause persistent central nervous system (CNS) infections in agammaglobulinemic individuals. Because these infections are rarely cured by passive administration of antibody, a chemotherapeutic approach would be advantageous. In this study, the efficacy of the antienterovirus (and antipicornavirus) drug disoxaril was demonstrated in a murine model of persistent enterovirus infection. Disoxaril is a hydrophobic antiviral compound that blocks picornavirus uncoating. The W-2 strain of human poliovirus type 2 (PV2) persists in the CNS of immunosuppressed mice and causes late paralysis. Mice were inoculated intracerebrally with PV2, immunosuppressed with cyclophosphamide, and treated intragastrically with disoxaril at 50, 100, or 200 mg/kg per day in two divided doses beginning on postinfection day 20. At 200 mg/kg per day, disoxaril significantly decreased the incidence of clinical disease, i.e., paralysis and death. Assays for virus revealed more rapid clearance of virus from the CNS in the drug-treated group. No drug-associated toxicity was observed. Residual isolates of virus were not drug-resistant, suggesting that the appearance of drug resistance during prolonged treatment may not be a clinical problem.

An evaluation of recent trends in preschool programming for hearing-impaired children

A longitudinal study was conducted of 139 children with severe and profound hearing losses. The children were between 3 and 5 years of age at the commencement of the 4-year study. The relationship of several background and educational variables with the linguistic, academic, and social development of the children was investigated. Age, hearing loss, and intelligence were related to most of the dependent measures. Relationships involving communication mode (auditory/oral vs. total communication) varied with the measure being considered. The variable of program type (individual vs. group) interacted with the degree of hearing loss and with communication mode. Although early intervention was related to certain dependent measures, no relationships were found that involved direct instruction by parents or integration.

Characterization of genetic changes occurring in attenuated poliovirus 2 during persistent infection in mouse central nervous systems

Genomic changes occurring in the attenuated W-2 strain of poliovirus 2 during persistent infection of the central nervous system of immunosuppressed mice were analyzed. The RNase T1 oligonucleotide fingerprints of 34 different viruses, isolated from the brains and spinal cords of paralyzed and nonparalyzed mice during a 105-day period, were used to quantitate and compare the mutations occurring in each isolate. Although mice were inoculated with plaque-purified virus, genetically distinct viruses were recovered from the central nervous system. The number of oligonucleotide changes occurring in isolates from paralyzed mice generally was greater than that observed in isolates from nonparalyzed mice. However, differences in the extent of mutation in isolates from the two groups of mice did not appear to be related to the level of virus replication. In paralyzed mice, the number of oligonucleotide changes on average was greater in viruses isolated during the first 60 days of the infection than in the last 45 days. The number of oligonucleotide changes was essentially constant throughout the infection, however, in viruses isolated from the brains of nonparalyzed mice. In addition, several specific oligonucleotide changes were found only in viruses isolated from paralyzed animals.