Supplementation of nutritional fluid and electrolyte balance by perfusion of an isolated small bowel loop in a patient with Crohn's disease

Delayed reanastamosis of small bowel in Crohn's disease has been made possible, largely by parenteral nutrition. We describe a patient with multiple resections resulting in loss of all the small and large bowel except the duodenum and 70 cms of proximal jejunum ending in a jejunostomy and a 150 cm long isolated loop of jejuno-ileum. The short proximal bowel proved adequate for energy and protein nutrition, with small frequent meals but gave rise to a persistent negative balance of water, sodium, potassium and magnesium. This was corrected by overnight perfusion of the isolated loop with an electrolyte solution with added glucose polymer to enhance sodium absorption. The critical rate of perfusion and concentration of glucose polymer were determined by a series of studies. The patient and her husband carried out this regimen for a year at home. The isolated loop was subsequently reanastamosed to the proximal jejunum allowing resumption of normal eating without further electrolyte disturbance.

Changing role of the oestrogen receptor in the life and death of breast cancer cells

The oestrogen receptor (ER) has proven to be an extraordinarily successful target for breast cancer treatment and prevention. The clinical use of tamoxifen, a nonsteroidal antioestrogen, demonstrated (1) that the strategic use of adjuvant tamoxifen in ER-positive patients could save lives and (2) that a selective ER modulator (SERM) could reduce the incidence of breast cancer in high-risk women. The ER is now the target for new and safer therapies such as the aromatase inhibitors and the pure antioestrogens that either block oestrogen synthesis or destroy the ER. However, the use of raloxifene, a SERM to prevent osteoporosis with the potential to prevent breast cancer has introduced a new dimension into preventive oncology. The widespread use of endocrine modulators (SERMs, aromatase inhibitors, and pure antioestrogens) raised the question of drug resistance. It is now clear that endocrine resistance can evolve through stages. Once a breast tumour becomes resistant to SERMs, the growth is stimulated by either the SERM or oestrogen. This is why an aromatase inhibitor is effective following SERM resistance and withdrawal. However, the extended use of repeated endocrine therapies now supersensitized the cells to oestrogen that causes apoptosis through the ER. We suggest that future clinical treatment strategies incorporate an 'oestrogen purge' to both enhance the actions of chemotherapy or completely reverse endocrine resistance and restore endocrine sensitivity. These new data build on the idea that breast cancer can be controlled as a chronic disease and will permit patients to live long and productive lives during targeted maintenance treatment.

Quinine suppresses extracellular potassium transients and ictal epileptiform activity without decreasing neuronal excitability in vitro

The effect of quinine on pyramidal cell intrinsic properties, extracellular potassium transients, and epileptiform activity was studied in vitro using the rat hippocampal slice preparation. Quinine enhanced excitatory post-synaptic potentials and decreased fast- and slow-inhibitory post-synaptic potentials. Quinine reduced the peak potassium rise following tetanic stimulation but did not affect the potassium clearance rate. Epileptiform activity induced by either low-Ca(2+) or high-K(+) artificial cerebrospinal fluid (ACSF) was suppressed by quinine. The frequency of spontaneous inter-ictal bursting induced by picrotoxin, high-K(+), or 4-aminopyridine was significantly increased. In normal ACSF, quinine did not affect CA1 pyramidal cell resting membrane potential, input resistance, threshold for action potentials triggered by intracellular or extracellular stimulation, or the orthodromic and antidromic evoked population spike amplitude. The main effects of quinine on intrinsic cell properties were to increase action potential duration and to reduce firing frequency during sustained membrane depolarizations, but not at normal resting membrane potentials. This attenuation was enhanced at increasingly depolarized membrane potentials. These results suggest that quinine suppresses extracellular potassium transients and ictal activity and modulates inter-ictal activity by limiting the firing rate of cells in a voltage-dependent manner. Because quinine does not affect 'normal' neuronal function, it may merit consideration as an anticonvulsant.

Significance of a prenatally diagnosed del(10)(q23)

Structural chromosome mosaicism is rare. We report a case of prenatal mosaicism for a deletion of chromosome 10(q23). To our knowledge, there are only three reports of prenatally diagnosed cases of del(10)(q23). Two of these cases were due to an inherited fragile site. In the present case amniocentesis revealed 46,XY,del(10)(q23)[9]/46,XY[45]. Follow-up chromosome analysis of peripheral blood and placental tissue from a phenotypically normal liveborn male revealed the del(10)(q23) in only 3/100 blood cells grown in low-folate medium. It appears that prenatally diagnosed deleted (10q) mosaicism represents culture artifact and is not clinically significant.

Distinct myoprotective roles of cardiac sarcolemmal and mitochondrial KATP channels during metabolic inhibition and recovery

The protective roles of sarcolemmal (sarc) and mitochondrial (mito) KATP channels are unclear despite their apparent importance to ischemic preconditioning. We examined these roles by monitoring intracellular calcium ([Ca]int), using fura-2 and fluo-3, in enzymatically isolated rat right ventricular myocytes. Myocyte mortality, estimated using a trypan blue assay, changed approximately in parallel with changes in [Ca]int. Chemically induced hypoxia (CIH), induced by application of cyanide and 2-deoxy-glucose, caused a steady rise in [Ca]int. Calcium increased more rapidly on 'reoxygenation' by return to control solutions. The protein kinase C (PKC) activator PMA abolished both phases of calcium increase. The mitoKATP channel-selective blocker 5-hydroxydecanoate partially prevented the PMA-induced protection during CIH, but not during reoxygenation. In contrast, HMR 1098, a sarcKATP channel-selective blocker, abolished protection only during the reoxygenation. Adenosine (A1) receptor activation prevented or reduced increases in [Ca]int and improved cell viability via a PKC and mito/sarcKATP channel-dependent mechanism. PKC-dependent protection against cytoplasmic calcium increases was also observed in a human cell line (tsA201) transiently expressing sarcKATP channels. Protection was abolished only during the reoxygenation phase by the amino acid substitution (T180A) in the pore-forming Kir6.2 subunit, a mutation previously shown to prevent PKC-dependent modulation. Our data suggest that sarc and mitoKATP channel populations play distinct protective roles, triggered by PKC and/or adenosine, during chemically induced hypoxia/reoxygenation.

Symbiotic gene activation is interrupted by endocrine disrupting chemicals

Endocrine disrupting chemicals (EDCs) include organochlorine pesticides, plastics manufacturing by-products, and certain herbicides. These chemicals have been shown to disrupt hormonal signaling in exposed wildlife, lab animals, and mammalian cell culture by binding to estrogen receptors (ER-+/- and ER-) and affecting the expression of estrogen responsive genes. Additionally, certain plant chemicals, termed phytoestrogens, are also able to bind to estrogen receptors and modulate gene expression, and as such also may be considered EDCs. One example of phytoestrogen action is genistein, a phytochemical produced by soybeans, binding estrogen receptors, and changing expression of estrogen responsive genes which certain studies have linked to a lower incidence of hormonally related cancers in Japanese populations. Why would plants make compounds that are able to act as estrogens in the human body? Obviously, soybeans do not intentionally produce phytoestrogens to prevent breast cancer in Japanese women.

Nitrogen fixation. Endocrine disrupters and flavonoid signalling

Nitrogen fixation is a symbiotic process initiated by chemical signals from legumes that are recognized by soil bacteria. Here we show that some endocrine-disrupting chemicals (EDCs), so called because of their effect on hormone-signalling pathways in animal cells, also interfere with the symbiotic signalling that leads to nitrogen fixation. Our results raise the possibility that these phytochemically activated pathways may have features in common with hormonal signalling in vertebrates, thereby extending the biological and ecological impact of EDCs.

Evidence for a novel natriuretic peptide receptor that prefers brain natriuretic peptide over atrial natriuretic peptide

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) exert their physiological actions by binding to natriuretic peptide receptor A (NPRA), a receptor guanylate cyclase (rGC) that synthesizes cGMP in response to both ligands. The family of rGCs is rapidly expanding, and it is plausible that there might be additional, as yet undiscovered, rGCs whose function is to provide alternative signalling pathways for one or both of these peptides, particularly given the low affinity of NPRA for BNP. We have investigated this hypothesis, using a genetically modified (knockout) mouse in which the gene encoding NPRA has been disrupted. Enzyme assays and NPRA-specific Western blots performed on tissues from wild-type mice demonstrate that ANP-activated cGMP synthesis provides a good index of NPRA protein expression, which ranges from maximal in adrenal gland, lung, kidney, and testis to minimal in heart and colon. In contrast, immunoreactive NPRA is not detectable in tissues isolated from NPRA knockout animals and ANP- and BNP-stimulatable GC activities are markedly reduced in all mutant tissues. However, testis and adrenal gland retain statistically significant, high-affinity responses to BNP. This residual response to BNP cannot be accounted for by natriuretic peptide receptor B, or any other known mammalian rGC, suggesting the presence of a novel receptor in these tissues that prefers BNP over ANP.

Dynamic modulation of cytoskeletal proteins linking integrins to signaling complexes in spreading cells. Role of skelemin in initial integrin-induced spreading

Recently we showed that signaling across beta3-integrin leads to activation of calpain and formation of integrin clusters that are involved in Rac activation. The subsequent activation of Rac and Rho leads to the formation of focal complexes and focal adhesions, respectively. The goal of the present study was to determine whether different proteins link the integrin to the cytoskeleton in the different complexes. We show that talin is present in focal adhesions but not in the calpain-induced clusters. alpha-Actinin colocalized with integrin at various sites, including the calpain-induced clusters. Skelemin, a protein shown recently to interact with beta1- and beta3-integrin in vitro, colocalized with integrin in calpain-induced clusters but was absent from focal adhesions. Cells transiently expressing skelemin C2 motifs, which contain the integrin binding site, failed to form integrin clusters or to spread on a substrate for beta1- and beta3-integrins. These results 1) suggest a dynamic reorganization of integrin complexes during cell spreading, 2) show that different cytoskeletal proteins link integrins in different complexes, and 3) demonstrate that skelemin is responsible for linking integrin to the calpain-induced clusters, and 4) show that the integrin-skelemin interaction is essential for transmission of signals leading to the initial steps of cell spreading.

Cytoskeletal proteins and platelet signaling

The actin filament network fills the cytoplasm of unstimulated platelets and connects with a submembranous latticework of short cross-linked actin filaments, known as the membrane skeleton. One function of the cytoskeleton is to direct the contours of the membrane in the unstimulated platelet and the rapid changes in shape in the activated platelet. Activation-induced changes result from events such as phosphorylation or calpain-induced cleavage of cytoskeletal proteins. The specific reorganizations depend upon the combination of signals to which platelets are exposed. A second function of the cytoskeleton is to bind other cellular components; it binds signaling molecules, localizing them to specific cellular locations; it binds the plasma membrane regulating properties of the membrane, maintaining microdomains in the membrane, or regulating activities of membrane proteins. In this way, the cytoskeleton plays a critical role in regulation of spatial organizations and, thus, in the integration of cellular activities.

Pressure-independent enhancement of cardiac hypertrophy in natriuretic peptide receptor A-deficient mice

Mice lacking natriuretic peptide receptor A (NPRA) have marked cardiac hypertrophy and chamber dilatation disproportionate to their increased blood pressure (BP), suggesting, in support of previous in vitro data, that the NPRA system moderates the cardiac response to hypertrophic stimuli. Here, we have followed the changes in cardiac function in response to altered mechanical load on the heart of NPRA-null mice (Npr1-/-). Chronic treatment with either enalapril, furosemide, hydralazine, or losartan were all effective in reducing and maintaining BP at normal levels without affecting heart weight/body weight. In the reverse direction, we used transverse aortic constriction (TAC) to induce pressure overload. In the Npr1-/- mice, TAC resulted in a 15-fold increase in atrial natriuretic peptide (ANP) expression, a 55% increase in left ventricular weight/body weight (LV/BW), dilatation of the LV, and significant decline in cardiac function. In contrast, banded Npr1+/+ mice showed only a threefold increase in ANP expression, an 11% increase in LV/BW, a 0.2 mm decrease in LV end diastolic dimension, and no change in fractional shortening. The activation of mitogen-activated protein kinases that occurs in response to TAC did not differ in the Npr1+/+ and Npr1-/- mice. Taken together, these results suggest that the NPRA system has direct antihypertrophic actions in the heart, independent of its role in BP control.

Prenatal diagnosis of trisomy 4 mosaicism

Trisomy 4 mosaicism is rare. To our knowledge only two cases of prenatally diagnosed trisomy 4 mosaicism have been reported. One case resulted in a normal liveborn male, the other resulted in an abnormal liveborn female. The karyotype of our case at the time of amniocentesis was 47,XY,+4[3]/ 46,XY[33] and resulted in a normal liveborn male. FISH analysis using an alpha satellite chromosome 4 probe was performed to confirm the cytogenetic findings. Follow-up chromosome analysis of cord blood, peripheral blood, foreskin, and umbilical cord fibroblasts showed a normal 46,XY male karyotype in all cells. FISH analysis of cord blood, umbilical cord fibroblasts, and amniotic fluid cells demonstrated two signals in 246 nuclei (i.e., 46,XY) and three signals in six nuclei (i.e., 47,XY,+4). Here we describe the present case of trisomy 4 mosaicism, the literature is reviewed, and the significance of this finding is discussed.

Evidence that beta3 integrin-induced Rac activation involves the calpain-dependent formation of integrin clusters that are distinct from the focal complexes and focal adhesions that form as Rac and RhoA become active

Interaction of integrins with the extracellular matrix leads to transmission of signals, cytoskeletal reorganizations, and changes in cell behavior. While many signaling molecules are known to be activated within Rac-induced focal complexes or Rho-induced focal adhesions, the way in which integrin-mediated adhesion leads to activation of Rac and Rho is not known. In the present study, we identified clusters of integrin that formed upstream of Rac activation. These clusters contained a Rac-binding protein(s) and appeared to be involved in Rac activation. The integrin clusters contained calpain and calpain-cleaved beta3 integrin, while the focal complexes and focal adhesions that formed once Rac and Rho were activated did not. Moreover, the integrin clusters were dependent on calpain for their formation. In contrast, while Rac- and Rho-GTPases were dependent on calpain for their activation, formation of focal complexes and focal adhesions by constitutively active Rac or Rho, respectively, occurred even when calpain inhibitors were present. Taken together, these data are consistent with a model in which integrin-induced Rac activation requires the formation of integrin clusters. The clusters form in a calpain-dependent manner, contain calpain, calpain-cleaved integrin, and a Rac binding protein(s). Once Rac is activated, other integrin signaling complexes are formed by a calpain-independent mechanism(s).

Signaling across the platelet adhesion receptor glycoprotein Ib-IX induces alpha IIbbeta 3 activation both in platelets and a transfected Chinese hamster ovary cell system

In platelets, alpha(IIb)beta(3) exists in a form that cannot bind adhesive proteins in the plasma; although it can interact with immobilized fibrinogen it cannot interact with immobilized von Willebrand factor in the vessel wall. Soluble agonists such as thrombin convert alpha(IIb)beta(3) to a form that recognizes soluble and immobilized ligands. Attempts to reconstitute alpha(IIb)beta(3) activation in a non-hematopoietic, nucleated cell system have been unsuccessful. In the present study, we have developed a transfected Chinese hamster ovary cell model in which alpha(IIb)beta(3) activation is induced by signaling across glycoprotein (GP) Ib-IX by its ligand, von Willebrand factor. GPIb-IX activates not only the transfected alpha(IIb)beta(3) but also endogenous alpha(v)beta(3). Activation of the pathways leading to integrin activation occurred even in cells transfected with GPIb-IX lacking the domain on GPIbalpha that binds 14-3-3 or that which binds actin-binding protein. These studies demonstrate that signals induced by interaction of GPIb-IX with von Willebrand factor lead to alpha(IIb)beta(3) activation and suggest that the signaling pathways by which GPIb-IX induces alpha(IIb)beta(3) activation are different to those used by thrombin. Elucidation of these differences may provide insights into therapeutic ways in which to inhibit integrin activation in selective clinical settings.

Sandalwood: the royal tree

Sandalwood is the most valuable tree in the world. As with gold, platinum and diamonds, it owes its value to a demand based on ritual, fashion and scarcity. It is the stuff of mystery and intrigue, and fortunes can still be made from it.

On the role of calpain and Rho proteins in regulating integrin-induced signaling

Integrin-induced adhesion of cells activates intracellular signaling pathways that lead to cytoskeletal reorganizations and altered cell behavior. One of the signaling molecules that is activated as a consequence of integrin-induced signaling is calpain. Much of the understanding of calpain's importance in signaling has come from the study of platelets. Studies on platelets have demonstrated that the major substrates for calpain are proteins present in the complexes of integrin, cytoskeletal proteins, and signaling molecules that form as a consequence of integrin engagement. We have now shown that calpain is also active in cultured adherent cells and that the calpain-induced cleavage of proteins in these cells is required for integrin-induced changes in cell morphology and spreading. Investigation of the mechanisms involved has revealed that calpain induces integrin-induced formation of focal adhesions and actin filament reorganizations and that it does so by inducing the activation of both Rac1 and RhoA.

Calpain mediates integrin-induced signaling at a point upstream of Rho family members

Integrin-induced adhesion leads to cytoskeletal reorganizations, cell migration, spreading, proliferation, and differentiation. The details of the signaling events that induce these changes in cell behavior are not well understood but they appear to involve activation of Rho family members which activate signaling molecules such as tyrosine kinases, serine/threonine kinases, and lipid kinases. The result is the formation of focal complexes, focal adhesions, and bundles and networks of actin filaments that allow the cell to spread. The present study shows that mu-calpain is active in adherent cells, that it cleaves proteins known to be present in focal complexes and focal adhesions, and that overexpression of mu-calpain increased the cleavage of these proteins, induced an overspread morphology and induced an increased number of stress fibers and focal adhesions. Inhibition of calpain with membrane permeable inhibitors or by expression of a dominant negative form of mu-calpain resulted in an inability of cells to spread or to form focal adhesions, actin filament networks, or stress fibers. Cells expressing constitutively active Rac1 could still form focal complexes and actin filament networks (but not focal adhesions or stress fibers) in the presence of calpain inhibitors; cells expressing constitutively active RhoA could form focal adhesions and stress fibers. Taken together, these data indicate that calpain plays an important role in regulating the formation of focal adhesions and Rac- and Rho-induced cytoskeletal reorganizations and that it does so by acting at sites upstream of both Rac1 and RhoA.

Identification of an interaction between the m-band protein skelemin and beta-integrin subunits. Colocalization of a skelemin-like protein with beta1- and beta3-integrins in non-muscle cells

Signaling across integrins is regulated by interaction of these receptors with cytoskeletal proteins and signaling molecules. To identify molecules interacting with the cytoplasmic domain of the beta3-integrin subunit (glycoprotein IIIa), a placental cDNA library was screened in the yeast two-hybrid system. Two identical clones coding for a 96-amino acid sequence were identified. This sequence was 100% identical to a sequence in skelemin, a protein identified previously in skeletal muscle. Skelemin is a member of a superfamily of cytoskeletal proteins that contain fibronectin-type III-like motifs and immunoglobulin C2-like motifs and that regulate the organization of myosin filaments in muscle. The amino acid residues in the isolated clones encompassed C2 motifs 4 and 5 of skelemin. A recombinant skelemin protein consisting of C2 motifs 3-7 interacted with beta1- and beta3-integrin cytoplasmic domains expressed as glutathione S-transferase (GST) fusion proteins, but not with GST-beta2-integrin cytoplasmic tail or GST alone. The skelemin-binding region was in the membrane proximal cytoplasmic domains of the integrins. Full-length skelemin interacted with integrin in intact cells as demonstrated by the colocalization of hemagglutinin-tagged skelemin in Chinese hamster ovary (CHO) cells containing alphaIIbbeta3-integrin and by the finding that microinjection of C2 motif 4 of skelemin into C2C12 mouse myoblast cells caused spread cells to round up. A skelemin-like protein was detected in CHO cells, endothelial cells, and platelets, and this protein colocalized with beta1- and beta3-integrins in CHO cells. This study suggests the presence of a skelemin-like protein in non-muscle cells and provides evidence that it may be involved in linking integrins to the cytoskeleton.

Sinorhizobium fredii and Sinorhizobium meliloti produce structurally conserved lipopolysaccharides and strain-specific K antigens

Lipopolysaccharides (LPS) and capsular polysaccharides (K antigens) may influence the interaction of rhizobia with their specific hosts; therefore, we conducted a comparative analysis of Sinorhizobium fredii and Sinorhizobium meliloti, which are genetically related, yet symbiotically distinct, nitrogen-fixing microsymbionts of legumes. We found that both species typically produce strain-specific K antigens that consist of 3-deoxy-D-manno-2-octulosonic acid (Kdo), or other 1-carboxy-2-keto-3-deoxy sugars (such as sialic acid), and hexoses. The K antigens of each strain are distinguished by glycosyl composition, anomeric configuration, acetylation, and molecular weight distribution. One consistent difference between the K antigens of S. fredii and those of S. meliloti is the presence of N-acetyl groups in the polysaccharides of the latter. In contrast to the K antigens, the LPS of Sinorhizobium spp. are major common antigens. Rough (R) LPS is the predominant form of LPS produced by cultured cells, and some strains release almost no detectable smooth (S) LPS upon extraction. Sinorhizobium spp. are delineated into two major RLPS core serogroups, which do not correspond to species (i.e., host range). The O antigens of the SLPS, when present, have similar degrees of polymerization and appear to be structurally conserved throughout the genus. Interestingly, one strain was found to be distinct from all others: S. fredii HH303 produces a unique K antigen, which contains galacturonic acid and rhamnose, and the RLPS did not fall into either of the RLPS core serogroups. The results of this study indicate that the conserved S- and RLPS of Sinorhizobium spp. lack the structural information necessary to influence host specificity, whereas the variable K antigens may affect strain-cultivar interactions.

Frequency and synchrony of tetanically-induced, gamma-frequency population discharges in the rat hippocampal slice: the effect of diazepam and propofol

Fast, rhythmic discharges, at gamma frequencies, have been evoked in the CA1 region of the hippocampus by tetanic stimulation applied via pairs of electrodes placed close to the pyramidal layer. The discharges had a latency of 65-225 ms and a frequency of 60-100 Hz; they were synchronous (phase lag < 2 ms) when recorded from sites 0.4-0.8 mm apart. Diazepam (5-15 microM) and propofol (5 microM) reduced the frequency by 15-26%, but had no significant effect on synchrony or phase lag, suggesting that the generation and synchrony of this rhythm are pharmacologically distinct. 10 microM propofol had a more marked effect and, when frequency fell by approximately 50%, synchrony was also reduced.

Prenatal diagnosis of low level trisomy 15 mosaicism: review of the literature

Low level chromosome mosaicism found at amniocentesis is problematic for clinicians and patients. We report prenatal diagnosis of a fetus with a rare karyotype of 47,XX, + 15/46,XX. Second trimester amniocentesis was performed for advanced maternal age. Fetal ultrasound revealed a hypoplastic right ventricle and intrauterine growth retardation (IUGR). The rest of the fetal anatomy was within normal limits. A mosaic karyotype of 47,XX, + 15/46,XX was observed. The couple interrupted the pregnancy at 19 weeks by dilation and suction evacuation. Careful evaluation of multiple pieces of fetal parts and placenta revealed one abnormal finding: a single umbilical artery. Cytogenetic metaphase and fluorescent in situ hybridization (FISH) interphase analyses of cells from fetal lung, heart, placenta, and skin revealed the presence of the trisomic line in all tissues. Molecular analysis demonstrated that the origin of the extra chromosome 15 was maternal, the error most likely occurred in meiosis I and the diploid line was of biparental inheritance. This case report discusses the associated findings in this fetus and reviews the literature describing other cases of mosaic trisomy 15.

Role of actin-binding protein in insertion of adhesion receptors into the membrane

The goal of this study was to determine whether actin-binding protein (ABP) regulates membrane composition. ABP-deficient and ABP-containing cells were transfected with the cDNAs coding for glycoprotein (GP) Ib-IX, a platelet receptor that interacts with ABP. Most of the GP Ib-IX remained inside the ABP-deficient cells. When ABP was present, functional GP Ib-IX was inserted into the membrane. GP Ib-IX lacking the domain that interacts with ABP also showed increased membrane insertion in ABP-expressing cells. Furthermore, a fragment of ABP that lacks the dimerization and GP Ib-IX-binding sites restored the spreading of the cells and increased the amount of GP Ib-IX in the membrane. Finally, expression of ABP also increased endogenous beta1 integrin in the membrane. These results indicate that 1) ABP maintains the properties of the cell such that adhesion receptors can be efficiently expressed in the membrane; 2) increased receptor expression is accompanied by increased ability of the cell to spread; and 3) ABP exerts its effect by a mechanism that does not appear to involve direct cross-linking of actin filaments or direct interaction with receptors.

Hypertension, cardiac hypertrophy, and sudden death in mice lacking natriuretic peptide receptor A

Natriuretic peptides, produced in the heart, bind to the natriuretic peptide receptor A (NPRA) and cause vasodilation and natriuresis important in the regulation of blood pressure. We here report that mice lacking a functional Npr1 gene coding for NPRA have elevated blood pressures and hearts exhibiting marked hypertrophy with interstitial fibrosis resembling that seen in human hypertensive heart disease. Echocardiographic evaluation of the mice demonstrated a compensated state of systemic hypertension in which cardiac hypertrophy and dilatation are evident but with no reduction in ventricular performance. Nevertheless, sudden death, with morphologic evidence indicative in some animals of congestive heart failure and in others of aortic dissection, occurred in all 15 male mice lacking Npr1 before 6 months of age, and in one of 16 females in our study. Thus complete absence of NPRA causes hypertension in mice and leads to cardiac hypertrophy and, particularly in males, lethal vascular events similar to those seen in untreated human hypertensive patients.

Identification of the region in actin-binding protein that binds to the cytoplasmic domain of glycoprotein IBalpha

Actin-binding protein (ABP-280) is a component of the submembranous cytoskeleton and interacts with the glycoprotein (GP) Ibalpha subunit of the GP Ib-IX complex in platelets. In the present studies, we have identified the binding site for GP Ibalpha in ABP-280. A melanoma cell line lacking ABP-280 was stably transfected with the cDNAs coding for GP Ib-IX, then transiently transfected with cDNA coding for various carboxyl-truncates of ABP-280. Immunocapture assays and co-immunoprecipitation experiments from detergent-lysed cells showed that deletion of the carboxyl-terminal repeats 20-24 of ABP-280 had no effect on GP Ib-IX binding, but deletion of residues 2099 through 2136 within repeat 19 abolished binding. In the yeast two-hybrid system, an ABP-280 fragment comprising repeats 17-19 bound GP Ibalpha. Deletion from either end abolished binding. Individual or multiple repeats of ABP-280 were expressed as fusion protein in bacteria and purified; structural folding was evaluated, and binding to GP Ib-IX was assessed. Binding depended on the presence of repeats 17-19. None of the individual repeats were able to bind to GP Ib-IX. These findings demonstrate that residues 1850-2136 comprising repeats 17-19 contain the binding site for GP Ib-IX.

Four sibs with arterial tortuosity: description and review of the literature

We described four offspring of a consanguineous couple with arterial tortuosity "syndrome" (ATS). The affected children had extensive arterial involvement although the clinical presentations were quite variable. Clinical manifestations included cutis laxa or soft/thin skin, joint laxity or contractures, and arachnodactyly. Aortic tortuosity and pulmonary artery aneurysms with or without peripheral stenoses were demonstrated in all four sibs. All three males had inguinal hernias. Inconsistent facial anomalies were downslanting palpebral tissues, beaked nose, micrognathia, and high-arched palate. Results of collagen type I and type III biosynthesis studies were normal on skin fibroblasts. Histologic findings on autopsy of one affected child showed arterial changes with disruption of elastic fibers of the media and fragmentation of the internal elastic membrane as well as mucosal and transmural necrosis of the stomach, small bowel, colon, and extensive necrosis of the liver. Coronary artery involvement was also seen in this child as well as biventricular hypertrophy. We conclude that ATS is an autosomal recessive connective tissue condition associated with diffuse arterial changes and involvement of the skin, joints, and other organs.

Platelet activation: new aspects

Work on growth factor receptors in other cells has led to the concept that tyrosine phosphorylation of receptor cytoplasmic domains leads to recruitment of signaling molecules to appropriate sub-membrane locations. Complexes of molecules are assembled through structural motifs that mediate phosphotyrosine-SH2 domain and SH3-proline-rich domain interactions. These interactions lead to activation of signaling molecules, especially activation of members of the Ras superfamily that in turn mediate downstream effects on gene regulation, vesicle movement, and cytoskeletal reorganizations. In platelets, signaling occurs primarily through members of the seven transmembrane-hererotrimeric G-protein coupled family of receptors and through adhesion receptors. The most rapid are of growth in recent years has been the realization that signaling through both G-protein coupled receptors and adhesion receptors is dependent on tyrosine kinase activation, recruitment of complexes of SH2, SH3, and proline-rich signaling molecules to appropriate locations in the cell, and on activation of members of the Ras superfamily of proteins. Because neither G-protein coupled receptors nor adhesion receptors have intrinsic tyrosine kinase activity, mechanisms presumably exist for using non-receptor kinases to initiate tyrosine phosphorylation reactions that in turn lead to the recruitment of signaling molecules. As discussed in this article, many tyrosine kinases exist in platelets and some of these are known to be tyrosine phosphorylated and activated following platelet activation. The theme that is emerging is that these tyrosine kinases may serve to phosphorylate submembranous proteins including receptors for cytoplasmic domains or components of the submembranous cytoskeleton of adhesion-receptor cytoskeleton complexes that can then recruit and activate appropriate signaling molecules. The challenge in future years will be to identity the way in which the activation of tyrosine kinase(s) is induced by receptor activation, identify the tyrosine kinase(s) involved, and identify the way in which specific members of the Ras superfamily activate downstream effectors to induce the responses of platelets to activation.

Conduction velocity in the forearm segment of the median nerve in patients with impaired conduction through the carpal tunnel

Conduction velocity, in the forearm segment of the median nerve, has been investigated in a group of patients with carpal tunnel syndrome. Motor conduction velocity was reduced below 50 m/s in 18% of the sample. Although a correlation between severity of compression and forearm motor conduction velocity was demonstrated, it was weak (r = 0.51) and slow forearm velocities occurred in some patients who had only a minor abnormality at the carpal tunnel itself. In patients with uncomplicated carpal tunnel syndrome, slow motor conduction in the forearm segment of the median nerve was accompanied by only a small reduction (approx. 5 m/s) in mixed nerve conduction velocity. By contrast, in patients whose abnormality at the carpal tunnel was accompanied by evidence of a more widespread sensorimotor neuropathy, mixed nerve conduction velocity was reduced in parallel with the change in motor conduction velocity.

The cytoplasmic domain of the alpha-subunit of glycoprotein (GP) Ib mediates attachment of the entire GP Ib-IX complex to the cytoskeleton and regulates von Willebrand factor-induced changes in cell morphology

The glycoprotein (GP) Ib-IX complex is one of the major platelet membrane glycoproteins. Its extracellular domain binds von Willebrand factor at a site of injury, an interaction that leads to activation of intracellular pathways. Its intracellular domain associates tightly with the platelet cytoskeleton through actin-binding protein. The goal of the present study was to investigate the role of the cytoplasmic domain of the GP Ib-IX complex and its interaction with the cytoskeleton. Cultured cells were transfected with the cDNAs coding for GP Ib(beta), GP IX, and full-length or truncated forms of GP Ib(alpha). Western blots of detergent-insoluble fractions of Triton X-100-lysed cells showed that deletion of amino acids Trp-570 to Ser-590 from the cytoplasmic domain of GP IB(alpha) abolished the interaction of the entire GP Ib-IX complex with the cytoskeleton. Truncated GP Ib(alpha) that was unable to associate with the cytoskeleton retained its ability to associate with GP Ib(beta), to be inserted into the membrane, and to bind von Willebrand factor. Cells expressing GP Ib(alpha) changed their shape following adhesion to immobilized von Willebrand factor. Cells expressing truncated GP Ib(alpha) also changed their shape following adhesion but showed a very different morphology as compared to cells expressing full-length GP Ib(alpha). These results show that GP Ib-IX-von Willebrand factor interactions lead to cytoskeletal reorganizations, that the cytoplasmic domain of GP Ib(alpha) regulates these reorganizations, and that the cytoplasmic domain of GP Ib(alpha) is absolutely required for attachment of the GP Ib-IX complex to the cytoskeleton.

Identification of a binding sequence for the 14-3-3 protein within the cytoplasmic domain of the adhesion receptor, platelet glycoprotein Ib alpha

The zeta-form 14-3-3 protein (14-3-3zeta) regulates protein kinases and interacts with several signaling molecules. We reported previously that a platelet adhesion receptor, glycoprotein (GP) Ib-IX, was associated with a 29-kDa protein with partial sequences identical to 14-3-3zeta. In this study, the interaction between GPIb-IX and recombinant 14-3-3zeta is reconstituted. Further, we show that the 14-3-3zeta binding site in GPIb is within a 15 residue sequence at the C terminus of GPIb-alpha, as indicated by antibody inhibition and direct binding of 14-3-3zeta to synthetic GPIb-alpha cytoplasmic domain peptides. The 14-3-3zeta binds to recombinant wild type GPIb-IX but not to the GPIb-alpha mutants lacking C-terminal 5 or more residues, suggesting that the C-terminal 5 residues of GPIb-alpha are critical. Similarity between the GPIb-alpha C-terminal sequence and the serine-rich regions of Raf and Bcr kinases suggests a possible serine-rich recognition motif for the 14-3-3 protein.

The platelet cytoskeleton stabilizes the interaction between alphaIIbbeta3 and its ligand and induces selective movements of ligand-occupied integrin

Previously, we showed that a subpopulation of the major platelet integrin, alphaIIbbeta3, co-sediments from detergent lysates with talin and other membrane skeleton proteins. Once alphaIIbbeta3 has bound adhesive ligand in a platelet aggregate, the detergent-insoluble alphaIIbbeta3 redistributes (along with the detergent-insoluble membrane skeleton proteins and a variety of signaling molecules) to a fraction that contains cytoplasmic actin filaments. Concomitantly, certain signaling molecules are activated. The present study shows that, in intact platelets, alphaIIbbeta3 forms clusters when occupied by ligand and is selectively moved into the open canalicular system; alphaIIbbeta3 that has not bound ligand remains diffusely distributed at the periphery of the cell. When cytoplasmic actin filaments are depolymerized by cytochalasins, the ability of alphaIIbbeta3 to bind ligand is decreased, and the movement of ligand-occupied alphaIIbbeta3 is prevented. Together with the previous findings, these results suggest that (i) membrane skeleton-associated alphaIIbbeta3 is selectively induced to bind ligand in activated platelets, (ii) ligand-induced transmembrane signaling causes an altered association of membrane skeleton-associated alphaIIbbeta3 with the cytoplasmic component of the cytoskeleton, (iii) ligand-induced cytoskeletal reorganizations stabilize the interaction between ligand and integrin, and (iv) ligand-occupancy triggers cytoskeletal reorganizations that result in selective movements of occupied ligand.

Infant with mos45,x/46,XY/47,XYY/48,XYYY: genetic and clinical findings

We describe an infant with mos45,X/46,XY/47,XYY/48,XYYY who presented with ambiguous genitalia. Her phenotype was also remarkable for minor ear and eye anomalies and coarctation of the aorta with bicuspid aortic valve. Laparoscopy revealed bilateral Fallopian tubes and a left infantile testis with epididymis. Chromosomal analyses of blood, skin, aorta, right Fallopian tube, and left gonadal tissue showed mos45,X/46,XY/47,XYY/48,XYYY. The 46,XY cell line was identified with routine trypsin-Giemsa banding only in cultured cells from an aortic biopsy. Fluorescence in-situ hybridization (FISH) was utilized to identify the presence of 46,XY cells in other tissues. The clinical manifestations of this patient are discussed and compared with those of similar cases of Y chromosome aneuploidy. To our knowledge, this is the first report of a patient with this unusual karyotype.

Dystrophin-related protein in the platelet membrane skeleton. Integrin-induced change in detergent-insolubility and cleavage by calpain in aggregating platelets

The platelet membrane is lined with a membrane skeleton that associates with transmembrane adhesion receptors and is thought to play a role in regulating the stability of the membrane, distribution and function of adhesive receptors, and adhesive receptor-induced transmembrane signaling. When platelets are lysed with Triton X-100, cytoplasmic actin filaments can be sedimented by centrifugation at low g-forces (15,600 x g) but the membrane skeleton requires 100,000 x g. The present study shows that DRP (dystrophin-related protein) sediments from lysed platelets along with membrane skeleton proteins. Sedimentation results from association with the membrane skeleton because DRP was released into the detergent-soluble fraction when actin filaments were depolymerized. Interaction of fibrinogen with the integrin alpha IIb beta 3 induces platelet aggregation, transmembrane signaling, and the formation of integrin-rich cytoskeletal complexes that can be sedimented from detergent lysates at low g-forces. Like other membrane skeleton proteins, DRP redistributed from the high-speed pellet to the integrin-rich low-speed pellet of aggregating platelets. One of the signaling enzymes that is activated following alpha IIb beta 3-ligand interactions in a platelet aggregate is calpain; DRP was cleaved by calpain to generate an approximately 140-kDa fragment that remained associated with the low-speed detergent-insoluble fraction. These studies show that DRP is part of the platelet membrane skeleton and indicate that DRP participates in the cytoskeletal reorganizations resulting from signal transmission between extracellular adhesive ligand and the interior of the cell.

Interaction of platelet glycoprotein V with glycoprotein Ib-IX regulates expression of the glycoproteins and binding of von Willebrand factor to glycoprotein Ib-IX in transfected cells

The goal of the present study was to determine whether platelet glycoprotein (GP) V interacts directly with the von Willebrand factor receptor GP Ib-IX and, if so, whether it affects the expression and function of this receptor. A melanoma cell line that does not contain actin-binding protein was transfected with the cDNAs coding for GP V and for each of the three subunits of GP Ib-IX. GP V co-immunoprecipitated and co-localized with GP Ib-IX. Although GP V could be expressed in the absence of GP Ib-IX, the amount incorporated in the membrane was markedly increased when GP Ib-IX was present. Similarly, there was an enhanced expression of GP Ib-IX on the cell surface in the presence of GP V. The binding affinity of botrocetin-induced von Willebrand factor to GP Ib-IX was unaffected by the presence or absence of GP V. However, the binding capacity was increased by the presence of GP V. We conclude that GP V interacts directly with GP Ib-IX, that GP V must associate with GP Ib-IX to be efficiently expressed in the membrane, and that GP V increases the binding capacity of the cells for von Willebrand factor by enhancing the surface expression of the GP Ib-IX complex.

Multiple peptide synthesis

The synthesis of large numbers of peptides can be very labor intensive and, if a conventional peptide synthesizer is used, only small numbers of peptides can be produced within a reasonable time. The techniques described below can make large numbers of different peptides simultaneously with varying degrees of mechanization, ranging from the wholly manual methods, to those involving complete mechanization of the whole synthesis process. Most of the multiple synthesis methods are primarily intended for small scale production ranging from microgram amounts up to a few tens of milligrams. All of the systems are economical in use of solvents and reagents, enabling cost-effective synthesis. The techniques described can also be used to prepare peptide libraries, containing several millions of peptide sequences, to enable the rapid screening of all possible permutations of amino acids within short peptides. However, it is considered that multiple synthesis methods are not particularly suited where extreme high purity or very long peptides are required.

Cytogenetic analysis of tissues from patients with familial paragangliomas of the head and neck

BACKGROUND

Paragangliomas of the head and neck are slow-growing tumors that originate from neural crest cells. Between 7% and 9% of these tumors have a familial occurrence. The suspected gene for familial paragangliomas (FP) is transmitted with an autosomal dominant mode of inheritance with incomplete penetrance, and appears to exhibit genomic imprinting. It has been demonstrated by family studies that individuals who inherit the gene(s) from their father will develop the disease. Through linkage analysis, the gene(s) for FP has been postulated to be located on the long arm of chromosome 11. The discovery of many different genes has been elucidated through the cytogenetic analysis of affected individuals who carry specific chromosome aberrations. This project was designed to look for chromosome abnormalities in several second-generation family members to further assist in the localization of the gene(s) for FP.

METHODS

This study involved the cytogenetic evaluation of lymphocytes, fibroblasts, and tumor cells of several second-generation family members from a three-generation family with FP of the head and neck to look for chromosome abnormalities generally, and for abnormalities of chromosome 11 specifically. Standard cytogenetic techniques were used for lymphocyte and fibroblast cultures. Tumor cells were cultured in a collagen matrix with F12 medium supplemented with 3% L-glutamine and 10% fetal calf serum.

RESULTS

There were no detectable abnormalities of chromosome 11 in any of the cells. However, nonrandom abnormalities of chromosomes 5 and 7 were seen in some of the tumor cells of one FP patient. To our knowledge, this is the first article which demonstrated the ability to successfully culture FP of the head and neck.

Transmembrane signaling across the platelet integrin glycoprotein IIb-IIIa

The platelet membrane is lined by a membrane skeleton, which in turn appears to be associated with underlying cytoplasmic actin filaments. Glycoprotein IIb-IIIa appears to associate with the membrane skeleton in unstimulated platelets. Upon platelet activation, unidentified intracellular signals cause GP IIb-IIIa to become competent to bind adhesive ligand. We suggest that the membrane skeleton may play a role in allowing this inside-out signaling. Signaling molecules that appear to associate with the membrane skeleton in unstimulated platelets include pp60c-src, pp62c-yes, and GAP. Preliminary evidence suggests that components of the membrane skeleton may become phosphorylated on tyrosine residues prior to GP IIb-IIIa-ligand interactions. Once GP IIb-IIIa binds adhesive ligand in a platelet aggregate, there is signaling in the opposite direction. One consequence of the outside-in transmembrane signaling is that the membrane skeleton becomes more tightly associated with the underlying actin filaments as focal contact-like structures form. Proteins that accumulate in these focal contact-like structures with a time course identical to that of GP IIb-IIIa and in a GP IIb-IIIa-dependent manner include talin, vinculin, and spectrin. Signaling molecules that accumulate in the focal contact-like structures include pp60c-src, pp62c-yes, phosphoinositide 3-kinase, and protein kinase C. These are potential candidates for the enzymes that mediate the ligand-induced transmembrane signaling. Another enzyme involved in the ligand-induced signaling is calpain. This enzyme is activated as a consequence of ligand-GP IIb-IIIa interactions and cleaves components of the membrane skeleton. Future experiments will be needed to identify other signaling enzymes activated as a consequence of GP IIb-IIIa interactions and to determine which ones are responsible for inducing the cytoskeletal reorganizations that occur in platelets and other cells when integrins bind their adhesive ligands.

Shedding of adhesion receptors from the surface of activated platelets

When platelets are activated, several receptors are removed from the platelet surface. Cytoskeletal reorganizations can cause receptors to redistribute to intracellular membranes. In addition, receptors can be removed from the platelet surface by shedding of the receptor from the cell. Shedding can occur by at least two mechanisms. First, glycoprotein (GP)Ib alpha and GP V are shed from the membrane as a result of the proteolytic cleavage of the extracellular domain of these receptors from the platelet. The protease responsible for this cleavage appears to be a membrane-bound divalent cation-dependent protease other than calpain. Proteolytic cleavage does not occur until secretion is well under way and occurs whether platelets aggregate or not. Soluble forms of both GP Ib alpha and GP V are present in the plasma, where they may serve as feedback inhibitors limiting the development of thrombi. Future studies will be needed to identify the protease(s) responsible for removing the membrane receptors and to determine whether cleavage of the receptors from activated platelets results from activation of the protease(s), exposure of the protease(s), or an altered exposure of the protease-sensitive sites on the receptors. It will be of particular interest to determine whether the protease(s) that cleaves GP Ib alpha and GP V in platelets is the same as the protease(s) that cleaves receptors from the surface of other activated cells. Receptors also are shed from the surface of activated platelets by the generation of microvesicles from the plasma membrane. These microvesicles appear to contain all of the major membrane glycoproteins but are depleted in those that have been removed from the platelet membrane by proteolytic cleavage. The primary mechanism responsible for the shedding of microvesicles from the surface of platelets stirred with physiological agonists involves activation of calpain, which cleaves components of the membrane skeleton and dissociates it from the plasma membrane GP Ib-IX complex. Microvesicles are present in the circulation and increase under conditions in which platelet activation is known to have occurred. Because they contain functional adhesive receptors and procoagulant activity on their surface, they may function to disseminate procoagulant activity and stabilize the formation of platelet clots.

Stimulation of fatty acid biosynthesis by dietary cholesterol and of cholesterol synthesis by dietary fatty acid

We reported previously that dietary cholesterol produces hypertriglyceridemia in the rat, accompanied by reduced oxidation and increased incorporation of exogenous fatty acid into hepatic triglyceride and increased secretion of very low density lipoprotein. We now report that dietary cholesterol also increases net hepatic fatty acid synthesis and the incorporation of newly synthesized fatty acid into hepatic triglyceride in vivo. Male rats were fed a cholesterol-free, semisynthetic diet (5% [w/w] corn oil) for 7 days, or the same diet supplemented with 0.5% cholesterol. On the day of the experiments, fed animals received 5 mCi 3H2O intraperitoneally (i.p.) either at 1200 h (6 h into the light cycle) or at 2400 h (6 h into the dark cycle). Animals were killed 1 h after receiving the radioisotope. Feeding cholesterol increased hepatic triglyceride and cholesteryl ester concentrations, moderately elevated the content of free cholesterol, but did not affect phospholipid levels. Increased net synthesis of fatty acids by livers of animals receiving cholesterol was observed during the dark period; a similar increase during the light period was also observed for incorporation of newly synthesized fatty acid into hepatic phospholipid and cholesteryl ester, although incorporation into triglyceride was of borderline significance (P < 0.06). In other experiments male rats were fed similar diets for 3, 7, or 21 days. Fed animals received 10 mCi 3H2O, i.p. (900-1000 h), and were killed 24 h later. Duration of feeding did not influence rates of net fatty acid synthesis or the stimulation by cholesterol of incorporation of newly synthesized fatty acid into hepatic triglyceride and cholesteryl ester.(ABSTRACT TRUNCATED AT 250 WORDS)

The platelet cytoskeleton

The platelet cytoskeleton contains two actin filament-based components. One is the cytoplasmic actin filaments which fill the cytoplasm and mediate contractile events. The other is the membrane skeleton, which coats the plasma membrane and regulates properties of the membrane such as its contours and stability. In the unstimulated platelet, only 30-40% of the actin is polymerized into filaments; the rest is thought to be prevented from polymerizing by the association of thymosin beta 4 with monomeric actin and by the association of gelsolin with the barbed ends of pre-existing actin filaments. When platelets are activated, there is a rapid increase in actin polymerization; new filaments fill the extending filopodia and form a network at the periphery of the platelet. As a result of activation, myosin binds to cytoplasmic actin filaments, causing them to move towards the center of the platelet. As platelets aggregate, additional cytoskeletal reorganizations occur: GP IIb-IIIa associates with adhesive ligand in a platelet aggregate; this results in the association of GP IIb-IIIa, membrane skeleton proteins, and signaling molecules with cytoplasmic actin. Future studies should help to elucidate the significance of the cytoskeleton in regulating signal transduction events in platelets.

On the role of the platelet membrane skeleton in mediating signal transduction. Association of GP IIb-IIIa, pp60c-src, pp62c-yes, and the p21ras GTPase-activating protein with the membrane skeleton

The platelet plasma membrane is lined with a membrane skeleton composed of short actin filaments, actin-binding protein, spectrin, vinculin, and other unidentified proteins. It is connected to the outside of the cell through association with the cytoplasmic domains of transmembrane receptors. In detergent-lysed platelets, cytoplasmic actin filaments are sedimented by centrifugation at 15,600 x g, but the sedimentation of membrane skeleton fragments requires higher g-forces (100,000 x g). In the present study, we show that the major platelet integrin, glycoprotein (GP) IIb-IIIa, sediments from detergent-lysed platelets at 100,000 x g together with fragments of the membrane skeleton that contain the cytoskeletal proteins spectrin, vinculin, and talin. In addition, this cell fraction contained the tyrosine kinases pp60c-src and pp62c-yes and the p21ras GTPase-activating protein (GAP). After thrombin-induced platelet aggregation mediated by fibrinogen binding to GP IIb-IIIa on adjacent platelets, we detected a redistribution of spectrin, talin, vinculin, pp60c-src, and pp62c-yes to the fraction that sediments at 15,600 x g. The redistribution of these proteins from the high-speed detergent-insoluble fraction to the low-speed fraction correlated with the extent of aggregation and was not detected in aggregation-defective thrombasthenic platelets (which lack the GP IIb-IIIa complex). In addition, many of the proteins phosphorylated on tyrosine in activated platelets were present in detergent-insoluble fractions. These results are consistent with the possibilities that 1) GP IIb-IIIa, pp60c-src, pp62c-yes, and GAP associate with a membrane skeleton fraction that contains spectrin, vinculin, and talin, 2) the association of GP IIb-IIIa with adhesive ligand in a platelet aggregate causes components of the membrane skeleton to undergo altered association with cytoplasmic actin filaments, and 3) many of the proteins phosphorylated on tyrosine residues in activated platelets are components of the cytoskeleton. The results imply that the membrane skeleton may play an important role in binding signaling molecules at sites of integrin-cytoskeleton interactions and in mediating signal transduction events in platelets. Further, GP IIb-IIIa-induced redistribution of components of the membrane skeleton and associated signaling molecules may represent an important step in regulating integrin-induced motile events in platelets.

A rare inherited euchromatic heteromorphism on chromosome 1

Extra genetic material that is euchromatic is generally regarded to be associated with phenotypic abnormalities. However, recent studies suggest that this is not always the case. Chromosome analysis was performed on amniotic fluid cells from a 37-year-old phenotypically normal patient referred for advanced maternal age. All the cells analysed showed a karyotype of 46,XY,1p+. The 1p+ chromosome had extra genetic material of uncertain origin in chromosome band region 1p21-->31. Chromosome analysis on the father revealed a normal 46,XY male karyotype. The mother's karyotype showed the same 1p+ chromosome. C and Q banding, as well as silver staining studies, in both the mother and the fetus support the interpretation that the extra chromosomal material was euchromatic in nature. This 1p+ chromosome may be characterized as a euchromatic heteromorphism. Euchromatic heteromorphisms not associated with phenotypic abnormalities have been reported for chromosomes 9 and 16. To the best of our knowledge, this is the first report involving this type of cytogenetic anomaly on chromosome number 1 in a phenotypically normal mother and infant.

Evidence that activation of platelet calpain is induced as a consequence of binding of adhesive ligand to the integrin, glycoprotein IIb-IIIa

Calpain (a Ca(2+)-dependent protease) is present in many cell types. Because it is present in the cytosol, the potential exists that it may regulate critical intracellular events by inducing crucial proteolytic cleavages. However, the concentrations of Ca2+ required to activate calpain are higher than those attained in the cytoplasm of most cells. Thus, the physiological importance of calpain and the mechanisms involved in its activation have remained elusive. In this study, we show that calpain rapidly moved to a peripheral location upon the addition of an agonist to suspensions of platelets, but it remained unactivated. We provide three lines of evidence that calpain was subsequently activated by a mechanism that required the binding of an adhesive ligand to the major platelet integrin, glycoprotein (GP) IIb-IIIa: calpain activation was prevented by RGDS, a tetrapeptide that inhibits the binding of adhesive ligand to GP IIb-IIIa; it was also prevented by monoclonal antibodies that inhibit adhesive ligand binding to GP IIb-IIIa; and its activation was markedly reduced in platelets from patients whose platelets have greatly reduced levels of functional GP IIb-IIIa. Thus, in platelets, binding of the extracellular domain of GP IIb-IIIa to its adhesive ligand can initiate a transmembrane signal that activates intracellular calpain. Because calpain is present in focal contacts of adherent cells, the interaction of integrins with adhesive ligands in the extracellular matrix may regulate activation of calpain in other cell types as well.