Murine NIMA-related kinases are expressed in patterns suggesting distinct functions in gametogenesis and a role in the nervous system

NIMA protein kinase is a major regulator of progression into mitosis in Aspergillus nidulans. Dominant negative forms of NIMA protein prevent entrance into mitosis in HeLa cells, suggesting that mammals have a similar pathway. We have reported previously the isolation of a murine NIMA-related kinase, designated Nek1, and more recently several additional NIMA-related human kinases have been cloned. The existence of several mammalian NIMA-related genes raises the questions of whether the different mammalian members have redundant, overlapping or distinct functions, and whether these functions are related to the role of NIMA in controlling mitosis. To address these questions we have studied the expression patterns of the different murine nek genes. To this end, we isolated a murine nek2 cDNA and compared its patterns of expression, during both gametogenesis and embryogenesis, to those of nek1. Both genes were highly expressed in developing germ cells, albeit in distinct patterns. In both females and males, nek1 is expressed much earlier than nek2, suggesting only limited ability for functional redundancy. Surprisingly, a striking specificity of nek1 expression was found: high levels of nek1 RNA were observed in distinct regions of the nervous system, most notably in neurons of the peripheral ganglia. These patterns suggest that the different mammalian NIMA-related kinases participate in different phases of the meiotic process and may also have functions other than cell cycle control.

recessive spotting: a linked locus that interacts with W/Kit but is not allelic

BACKGROUND

The murine coat-colour mutation recessive spotting (rs) maps very closely to the W/Kit locus, encoding the proto-oncoprotein Kit, the protein tyrosine kinase receptor for stem cell factor. Kit is important in the development of melanocytes, germ cells, interstitial cells of Cajal (ICC) and haemopoietic lineages, including mast cells. rs has never been genetically separated from Kit, and interacts with Kit mutations, suggesting that it is a recessive allele of Kit. Here we have tested this possibility. We have shown previously that diploid rs/rs melanocytes proliferated more slowly than did +/+ melanocytes, as did an immortal line of rs/rs melanocytes, melan-rs.

RESULTS

The Kit mRNA level in rs/rs melanocytes was indistinguishable from that of other melanocyte lines. The Kit cDNA sequence from rs/rs melanocytes and the kinase activity of Kit in rs/rs mast cells appeared to be normal. No deficiency of mast cells or ICC was observed in rs/rs mice. Moreover, following the overexpression of a normal Kit cDNA, proliferation of rs/rs melanocytes was retarded further, but that of +/+ melanocytes was increased, indicating an intracellular interaction between rs and Kit. Of other closely linked tyrosine kinase genes, melanocytes and melanoblasts did not express mRNA for Pdgfra, Flk-1 or Txk, but both expressed Tec, encoding a nonreceptor kinase that interacts with Kit.

CONCLUSIONS

rs is not a mutation in Kit, although we have confirmed that rs interacts with Kit. It seems unlikely that rs affects Pdgfra, Flk-1 or Txk, but Tec remains a candidate for rs.

Retrospective evaluation of postoperative intralesional steroid injections on wound healing

Steroids have been implicated as an etiology in delayed wound healing. Although there is much documentation in the literature that steroids delay wound healing, most studies are in vitro or use high systemic doses. No studies have used a one-time, postoperative, intralesional steroid injection and evaluated wound healing. This study retrospectively reviewed 73 patients with 115 foot and ankle surgeries over 12 years. Seventy-two patients had steroid injections and 43 did not. The average healing time for the steroid group was 17.1 +/- 10.5 days, and for the non-steroid group 17.3 +/- 8.75 days. There were two infections in the non-steroid group, and one infection in the steroid group. There were five dehiscences in each group. The patients were further subdivided into groups based on age, gender, number of procedures, type of surgery, health status, steroid type, and steroid dose. The healing time increased in patients > 60 years old, and in immunocompromised patients. The patients who had more complex surgery had increased healing time. The males had a longer healing time than the females. Overall, there was not a statistically significant difference between the steroid groups and the non-steroid group. Therefore, one-time postoperative intralesional steroid injections were not found to delay wound healing.

Developmental origin and Kit-dependent development of the interstitial cells of cajal in the mammalian small intestine

Interstitial cells of Cajal (ICCs) form a network of cells between the external longitudinal and circular muscle layers at the level of the Auerbach's plexus in the mammalian small intestine. These cells express the Kit receptor tyrosine kinase and are essential for intestinal pacemaker activity. W mutant mice carrying structural mutations in the Kit gene lack both the network of ICCs and intestinal pacemaker activity. We were interested in the developmental origin of the cells that make up the network of ICCs. In addition, the specific stages of ICC development that require a functional Kit receptor have not been characterized. We show that ICCs originate from mesenchymal progenitor cells that coexpress both Kit and smooth muscle myosin heavy chain, a marker specific for smooth muscle, during embryogenesis. ICC and longitudinal smooth muscle lineages begin to diverge late in gestation. Embryos homozygous for the regulatory Wbanded (Wbd) mutation do not express Kit in these mesenchymal progenitor cells. Nevertheless, Wbd/Wbd mice display a normal network of ICCs and normal smooth muscle layers at postnatal day 5 (p5). Adult Wbd/Wbd mice lack a functional ICC network and intestinal pacemaker activity due to a failure of the ICCs to increase in numbers after p5. These data suggest a common developmental origin of the ICCs and the longitudinal smooth muscle layers in the mammalian small intestine and show that Kit expression is necessary for the postnatal development and proliferation of ICCs but not for the initial cell lineage decision toward an ICC fate during embryogenesis or for smooth muscle development.

Ischemic stroke and use of estrogen and estrogen/progestogen as hormone replacement therapy

BACKGROUND AND PURPOSE

Information about the risk of stroke in current postmenopausal hormone users is limited.

METHODS

In this case-control study, women aged 45 to 74 years hospitalized with a fatal or nonfatal stroke in any of 10 Northern California Kaiser Permanente facilities during the period November 1991 to November 1994 were identified as cases. Controls were selected at random from female Health Plan members. Data regarding use of estrogen plus progestogen or estrogen alone were obtained in interviews.

RESULTS

The analysis was based on nonproxy responses from 349 cases of ischemic stroke and 349 matched control subjects. After adjustment for confounders, the odds ratio for ischemic stroke in current hormone users was 1.03 (95% confidence interval, 0.65 to 1.65). The odds ratios for ischemic stroke in current hormone users showed no clear trend of increasing or decreasing risk in relation to duration of hormone use. The odds ratio for ischemic stroke in past hormone users was 0.84 (95% confidence interval, 0.54 to 1.32).

CONCLUSIONS

In this study postmenopausal hormone use was not associated with an increase or decrease in the risk of ischemic stroke, a finding that is consistent with the body of literature on this topic.

Developmental origin and Kit-dependent development of the interstitial cells of cajal in the mammalian small intestine

Interstitial cells of Cajal (ICCs) form a network of cells between the external longitudinal and circular muscle layers at the level of the Auerbach's plexus in the mammalian small intestine. These cells express the Kit receptor tyrosine kinase and are essential for intestinal pacemaker activity. W mutant mice carrying structural mutations in the Kit gene lack both the network of ICCs and intestinal pacemaker activity. We were interested in the developmental origin of the cells that make up the network of ICCs. In addition, the specific stages of ICC development that require a functional Kit receptor have not been characterized. We show that ICCs originate from mesenchymal progenitor cells that coexpress both Kit and smooth muscle myosin heavy chain, a marker specific for smooth muscle, during embryogenesis. ICC and longitudinal smooth muscle lineages begin to diverge late in gestation. Embryos homozygous for the regulatory Wbanded (Wbd) mutation do not express Kit in these mesenchymal progenitor cells. Nevertheless, Wbd/Wbd mice display a normal network of ICCs and normal smooth muscle layers at postnatal day 5 (p5). Adult Wbd/Wbd mice lack a functional ICC network and intestinal pacemaker activity due to a failure of the ICCs to increase in numbers after p5. These data suggest a common developmental origin of the ICCs and the longitudinal smooth muscle layers in the mammalian small intestine and show that Kit expression is necessary for the postnatal development and proliferation of ICCs but not for the initial cell lineage decision toward an ICC fate during embryogenesis or for smooth muscle development.

Embryonic and adult expression patterns of the Tec tyrosine kinase gene suggest a role in megakaryocytopoiesis, blood vessel development, and melanogenesis

The Tec cytoplasmic tyrosine kinase is a member of a family of src-like proteins that are thought to play important roles in hematopoiesis. Here we describe the temporal and spatial expression of the Tec gene during embryogenesis and in the adult. Our data demonstrate that embryonic Tec expression is restricted to distinct hematopoietic cells as well as structures and cell types that share a common feature of containing fluid in an enclosed cavity, e.g., endothelial cells. In addition, Tec is expressed in melanocytes late in gestation. The observed developmental expression pattern of Tec suggests a role for this gene in several aspects of hematopoiesis and/or blood vessel development as well as in late stages of melanogenesis.

Formed by thalidomide: mass torts as a false cure for toxic exposure

Professor Bernstein considers a theme of Judge Weinstein's judicial and academic writings--that tort law works imperfectly to effect justice in mass disaster cases--through the vehicle of thalidomide, the paradigmatic toxic substance. Thirty-five years ago, thalidomide poisoned thousands of children, inflicting limb-reduction birth defects. Professor Bernstein argues that the drug has also had a malforming effect on mass tort law. Courts and scholars have used the precedent of thalidomide to build stringent legal standards of proof and causation, without enough attention to the functions and consistency of these standards. Thalidomide has also prompted commentators to celebrate American drug regulation and the American liability system; Professor Bernstein argues that these paeans are exaggerated. She concludes that the United States must confront its thalidomide history, as other nations in the world have done, and build social institutions--strong regulation and social insurance--to guard against toxic disasters of the future.

Impaired CD28-mediated interleukin 2 production and proliferation in stress kinase SAPK/ERK1 kinase (SEK1)/mitogen-activated protein kinase kinase 4 (MKK4)-deficient T lymphocytes

The dual specific kinase SAPK/ERK1 kinase (SEK1; mitogen-activated protein kinase kinase 4/Jun NH2 terminal kinase [ JNK] kinase) is a direct activator of stress-activated protein kinases ([SAPKs]/JNKs) in response to CD28 costimulation, CD40 signaling, or activation of the germinal center kinase. Here we show that SEK1(-/-) recombination-activating gene (RAG)2(-/-) chimeric mice have a partial block in B cell maturation. However, peripheral B cells displayed normal responses to IL-4, IgM, and CD40 cross-linking. SEK1(-/-) peripheral T cells showed decreased proliferation and IL-2 production after CD28 costimulation and PMA/Ca2+ ionophore activation. Although CD28 expression was absolutely crucial to generate vesicular stomatitis virus (VSV)-specific germinal centers, SEK1(-/-)RAG2(-/-) chimeras mounted a protective antiviral B cell response, exhibited normal IgG class switching, and made germinal centers in response to VSV. Interestingly, PMA/Ca2+ ionophore stimulation, which mimics TCR-CD3 and CD28-mediated signal transduction, induced SAPK/JNK activation in peripheral T cells, but not in thymocytes, from SEK1(-/-) mice. These results show that signaling pathways for SAPK activation are developmentally regulated in T cells. Although SEK1(-/-) thymocytes failed to induce SAPK/JNK in response to PMA/Ca2+ ionophore, SEK1(-/-)RAG2(-/-) thymocytes proliferated and made IL-2 after PMA/Ca2+ ionophore and CD3/CD28 stimulation, albeit at significantly lower levels compared to SEK1(+/+)RAG2(-/-) thymocytes, implying that CD28 costimulation and PMA/Ca2+ ionophore-triggered signaling pathways exist that can mediate proliferation and IL-2 production independently of SAPK activation. Our data provide the first genetic evidence that SEK1 is an important effector molecule that relays CD28 signaling to IL-2 production and T cell proliferation.

Mutations in the murine fitness 1 gene result in defective hematopoiesis

Identification and characterization of mutations that disrupt normal hematopoiesis are essential for understanding the genetic pathways that control the development and regulation of the mammalian hematopoietic system. Previously, the fitness 1 gene was identified by five, independent mutations in N-ethyl-N-nitrosourea (ENU) saturation mutagenesis experiments within the albino (c) region of mouse chromosome 7 (MMU7). We report here that fit1 mutants are anemic, display numerous peripheral blood defects, and are deficient in early hematopoietic progenitor cell populations. The number of both erythroid and myeloid progenitors, as well as B cells, are reduced. These results implicate fit1 involvement in normal hematopoiesis and suggest that further characterization of the fit1 gene, and the five presumed point mutations of the gene, will lead to an improved understanding of normal hematopoiesis in the mouse.

A requirement for Flk1 in primitive and definitive hematopoiesis and vasculogenesis

Mouse embryos lacking the receptor tyrosine kinase, Flk1, die without mature endothelial and hematopoietic cells. To investigate the role of Flk1 during vasculogenesis and hematopoiesis, we examined the developmental potential of Flk1-/- embryonic stem cells in chimeras. We show that Flk1 is required cell autonomously for endothelial development. Furthermore, Flk1-/- cells do not contribute to primitive hematopoiesis in chimeric yolk sacs or definitive hematopoiesis in adult chimeras and chimeric fetal livers. We also demonstrate that cells lacking Flk1 are unable to reach the correct location to form blood islands, suggesting that Flk1 is involved in the movement of cells from the posterior primitive streak to the yolk sac and, possibly, to the intraembryonic sites of early hematopoiesis.

A comparison of physician and hospital use among the nonelderly covered by HMOs and indemnity insurance

This article uses data from the 1992 National Health Interview Survey to compare medical services use between chronically ill nonelderly people with health maintenance organization (HMO) or indemnity insurance. The authors estimated regressions for two subgroups of privately insured individuals: those with 1 or more of 15 chronic conditions and those who reported their health as being fair or poor. For the subgroup with chronic conditions, HMO members were more likely to have a physician visit, controlling for other factors, than their indemnity counterparts. The authors found no differences in the likelihood of having a hospital stay or in the number of hospital days for those with at least one stay. Finally, for the subgroup who reported their health as being fair or poor, the authors found no differences in service use between HMO members and similar people in indemnity plans.

Femtosecond autocorrelation measurements based on two-photon photoconductivity in ZnSe

Two-photon photoconductivity in ZnSe is used to record femtosecond autocorrelation functions. This technique requires <100 muW of average power of a typical mode-locked femtosecond Ti:sapphire laser and distinguishes itself by a dynamic range over several decades and great conversion bandwidth, permitting the sensitive correlation of pulses of a few femtoseconds.

Dantrolene sodium reduces the enhanced leakage of creatine kinase caused by ethanol, cocaine, and electrical stimulation in isolated fast and slow muscles of rat

Binge drinking of alcohol, cocaine overdose, or overexertion can lead to rhabdomyolysis characterized by elevated creatine kinase (CK) and myoglobin in the serum, myoglobinuria, and muscle tenderness. Our previous studies showed that ethanol, cocaine, and electrical stimulation enhanced the leakage of CK from isolated soleus and extensor digitorum longus (EDL) muscles of rat. Dantrolene sodium was reported to reduce the muscle damage and elevated serum CK levels in exercised rats. The present study was aimed at testing whether dantrolene can reduce the enhanced leakage of CK from isolated rat soleus and EDL muscles caused by ethanol, cocaine, and electrical stimulation. After 4-hr incubation in oxygenated physiological solution at 37 degrees C, the mean leakage of CK was 1.56 units/mg of muscle in soleus and 0.89 units/mg in EDL. Ethanol at 0.2% increased the leakage of CK by 47% (p < 0.05) in soleus and by 26% in EDL. Cocaine at 1 mM increased the leakage of CK by 55% (p < 0.05) in soleus and by 27% in EDL. Electrical stimulation at 1 Hz for 4 hr increased the mean leakage of CK by 100% (p < 0.05) in soleus and 127% (p < 0.05) in EDL. Dantrolene sodium reduced the enhanced leakage of CK caused by ethanol, cocaine, and electrical stimulation significantly in soleus and slightly in EDL. Dantrolene may involve myoplasmic free Ca2+ in these beneficial effects as in malignant hyperthermia, and may be useful in the treatment of rhabdomyolysis associated with acute alcoholic myopathy, cocaine overdose, and overexertion.

Deregulated inflammatory response in mice lacking the STK/RON receptor tyrosine kinase

Immune and inflammatory responses must be rightly regulated to maintain a homoeostatic balance between an effective immune response and tissue damage to the host. NO is a principal mediator of many of the cytokine-inducible macrophage activities during a normal cell-mediated immune response. STK, the murine homologue of the human RON receptor tyrosine kinase, is expressed on murine resident peritoneal macrophages. The ligand for STK, macrophage-stimulating protein (MSP), is a serum protein that is activated by members of the coagulation cascade in response to tissue damage. In addition to its potential to induce chemotaxis and phagocytosis of C3bi-coated erythrocytes, MSP has an inhibitory effect on the production of NO by activated peritoneal macrophages in vitro. Here we demonstrate that peritoneal macrophages from mice lacking STK produce elevated levels of NO in response to interferon (IFN)-gamma in a dose-dependent manner, without the need for a co-stimulus. However, production of pro-inflammatory cytokines by activated macrophages from stk -/- mice is unaltered. In vivo, stk -/- mice exhibit increased inflammation in an IFN-gamma-mediated delayed-type hypersensitivity reaction and increased susceptibility to lipopolysaccharide (LPS)-induced endotoxic shock. Furthermore, the levels of NO in the serum of mice injected with LPS are significantly higher than those in control littermates. Nevertheless, the serum levels of IFN-gamma and the intermediate cytokines generated by the inflammatory response, which have previously been shown to play a role in septicaemic shock, do not differ significantly from controls. These data suggest that the STK receptor suppresses NO production, therefore ameliorating the potentially tissue-damaging effects of a cell-mediated immune response, through negative regulation of the IFN-gamma signalling pathway.

Incidence of stroke and myocardial infarction in women of reproductive age

BACKGROUND AND PURPOSE

Information on the incidence of vascular disease in women of reproductive age has been limited. These disease are rare in this age group, and a large population base is required for reliable estimation of incidence.

METHODS

For a case-control study of vascular disease and low-dose oral contraceptive use, we used emergency department logs and hospital admission and discharge records to ascertain fatal and nonfatal cases of first-ever stroke and myocardial infarction (MI) in women 15 to 44 years of age who were-members of a large California HMO. Incidence rates of stroke and MI were calculated on the basis of these data.

RESULTS

The incidence of MI not associated with pregnancy was 5.0 per 100,000 women-years. The incidence of stroke not associated with pregnancy was 10.7 per 100,000 women-years. MI was very rare until age 35 years. At every age, about half of hemorrhagic strokes were due to subarachnoid hemorrhage.

CONCLUSIONS

The incidence rates of stroke and MI are low in women of reproductive age in the United States.

Stress-signalling kinase Sek1 protects thymocytes from apoptosis mediated by CD95 and CD3

Distinct and evolutionarily conserved signal transduction cascades mediate survival or death in response to developmental and environmental cues. The stress-activated protein kinases, or Jun N-terminal kinases (SAPKs/JNKs), are activated in response to a variety of cellular stresses such as changes in osmolarity and metabolism, DNA damage, heat shock, ischaemia, or inflammatory cytokines. Sek1 (JNKK/MKK4) is a direct activator of SAPKs/JNKs in response to environmental stresses or mitogenic factors. Here we investigate the role of Sek1 in development and apoptosis by deleting sek1 in embryonic stem (ES) cells by homologous recombination. We provide genetic evidence that different stresses utilize distinct signalling pathways for SAPK/JNK activation. sek1(-/-) rag2(-/-) chimaeric mice have normal numbers of mature T cells but fewer immature CD4+CD8+ thymocytes. The sek1 mutation did not affect the induction of apoptosis in response to environmental stresses in ES and T cells: instead, sek1 protected thymocytes from CD95 (Fas)- and CD3-mediated apoptosis. These data indicate that SEK1 mediates survival signals in T-cell development.

Long-range genomic rearrangements upstream of Kit dysregulate the developmental pattern of Kit expression in W57 and Wbanded mice and interfere with distinct steps in melanocyte development

Mutations in the murine dominant white spotting (W) locus cause pleiotropic developmental defects that affect hematopoietic cells, melanocytes, germ cells and the interstitial cells of Cajal in the gut. W mutations either alter the coding sequence of the Kit receptor tyrosine kinase, resulting in a receptor with impaired kinase activity, or affect Kit expression. Here we describe the molecular and cell-type-specific developmental defects of two of the latter class of regulatory W alleles, W57 and Wbanded(bd). In both mutants, the temporal and spatial patterns of Kit expression are dysregulated during embryogenesis and in adult animals. In Wbd mice, ectopic expression of Kit in the dermatome of the somites at days 10.8 and 11.8 of development seemed to interfere with melanoblast development. In contrast, the W57 allele leads to an intrinsic pigmentation defect by downregulating developmental Kit expression in trunk melanoblasts, but not melanoblasts around the otic vesicle. Both mutations affect transcriptional initiation of the Kit gene. The W57 allele is associated with a 80 kb deletion 5′ of the Kit-coding region while Wbd is associated with a 2.8 Mb genomic inversion of chromosome 5 with the distal breakpoint between Kit and the platelet-derived growth factor receptor alpha (Pdgfra) gene, and the proximal breakpoint between the genes for the GABA receptor beta 1 (Gabrb1) and the Tec tyrosine kinase, juxtaposing the Kit and Tec tyrosine kinase genes. Neither W57 nor Wbd affect genomic sequences previously suggested in in vitro experiments to control cell-type-specific expression of Kit. These results link specific mechanisms of cellular and developmental defects to long-range genomic rearrangements that positively and negatively affect Kit transcription in different cell lineages as well as in different subpopulations of the same lineage.

Oncogenic mutation in the Kit receptor tyrosine kinase alters substrate specificity and induces degradation of the protein tyrosine phosphatase SHP-1

Activating mutations in the Kit receptor tyrosine kinase have been identified in both rodent and human mast cell leukemia. One activating Kit mutation substitutes a valine for aspartic acid at codon 816 (D816V) and is frequently observed in human mastocytosis. Mutation at the equivalent position in the murine c-kit gene, involving a substitution of tyrosine for aspartic acid (D814Y), has been described in the mouse mastocytoma cell line P815. We have investigated the mechanism of oncogenic activation by this mutation. Expression of this mutant Kit receptor tyrosine kinase in a mast cell line led to the selective tyrosine phosphorylation of a 130-kDa protein and the degradation, through the ubiquitin-dependent proteolytic pathway, of a 65-kDa phosphoprotein. The 65-kDa protein was identified as the src homology domain 2 (SH2)-containing protein tyrosine phosphatase SHP-1, a negative regulator of signaling by Kit and other hematopoietic receptors, and the protein product of the murine motheaten locus. This mutation also altered the sites of receptor autophosphorylation and peptide substrate selectivity. Thus, this mutation activates the oncogenic potential of Kit by a novel mechanism involving an alteration in Kit substrate recognition and the degradation of SHP-1, an attenuator of the Kit signaling pathway.

Update on adolescent health care in pediatric practice

PURPOSE

To determine current adolescent health care practices of pediatricians and evaluate whether changes have taken place during the past decade.

METHODS

A questionnaire completed by 101 pediatricians in 1985 was abbreviated and adapted by Committee on Youth of Chapter 2, District II of the American Academy of Pediatrics and sent to 1,633 members of the Chapter in June 1993.

RESULTS

Forty-three percent of the 436 respondents in 1993 were female, 43% < or = 40 years of age and 53% were in private practice. Most accept new patients > or = 16 years of age (76%), continue to see patients > or = 19 years of age (63%), and interview adolescents without their parents (86%). Although between one-third and two-thirds of respondents report having equipment for gynecologic examinations, most indicate they are "not entirely comfortable" treating adolescent issues and therefore refer to others for management. Between one-quarter and one-half indicate they are "very interested" in learning more about adolescent issues and an additional 40-50% are "somewhat interested." Obstacles to providing adolescent care include: "image as a baby doctor" (65%), fear that parents would object (61%), no separate hours (57%), difficulty in providing confidential care (56%), and difficulty in charging appropriate fees (47%). Females and younger pediatricians are more comfortable with some aspects of gynecologic care and more likely to be satisfied with the adolescent care they are providing. There were few differences between responses in 1993 and 1995.

CONCLUSIONS

Few of the pediatricians surveyed provide comprehensive care to adolescent patients. Future policy decisions and medical education must respond to these realities in pediatric practice.

A long-term study of symptoms, spirometry and survival amongst home nebulizer users

Although home nebulizers are widely used to deliver bronchodilator medication to patients with asthma and chronic obstructive pulmonary disease (COPD), the long-term benefits and hazards are unknown. The present authors have previously reported a prospective 12-month study of home nebulizer use involving 49 patients (15 asthma, mean forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) 1.3/2.1 1; 34 COPD, mean FEV1/FVC 0.7/1.8 1). Thirty-two of these patients were treated with long-term domiciliary nebulized bronchodilator treatment, the other 17 patients chose metered dose inhaler (MDI) therapy. The present paper reports the progress of these patients over 5 yr. Five-year survival was similar in both groups (nebulizer users 56%, MDI users 53%). Most deaths were due to respiratory failure (14 deaths) or lung cancer (four deaths). Survival was determined mainly by FEV1 (R = 0.54, P = 0.0001) and age (R = -0.47, P = 0.0007). Laboratory lung function tests (16 nebulizer users) showed that FEV1 and FVC were still higher than pre-nebulizer baseline measurements after 36 months of nebulizer use, but PEFR had fallen by 7%. Twenty-one of 23 surviving nebulizer users completed a questionnaire after 36 months of treatment. All used their nebulizer at least once per day and 20 of 21 patients reported that they still obtained full benefit from each nebulized treatment. The morning peak flow response to nebulized treatment was the same at baseline and at 36 months (48 1 min-1). All patients remained breathless (mean subjective score 4.8 on seven-point scale) but the subjective response to nebulized treatment was unchanged at 36 months. Tachyphylaxis did not develop among 13 patients who underwent repeated reversibility studies using 200 micrograms of salbutamol at 6, 12 and 36 months. It is concluded that home nebulizer therapy is safe and effective for a small number of carefully selected patients with severe asthma or COPD, who have been evaluated by a rigorous home nebulizer assessment protocol prior to commencing home nebulizer therapy.

A novel family of repeat sequences in the mouse genome responsive to retinoic acid

Repetitive DNA sequences form a substantial portion of eukaryotic genomes and exist as members of families that differ in copy number, length, and sequence. Various functions, including chromosomal integrity, gene regulation, and gene rearrangement have been ascribed to repetitive DNA. Although there is evidence that some repetitive sequences may participate in gene regulation, little is known about how their own expression may be regulated. During the course of gene trapping experiments with embryonic stem (ES) cells, we identified a novel class of expressed repetitive sequences in the mouse, using 5' rapid amplification of cDNA ends-polymerase chain reaction (5' RACE-PCR) to clone fusion transcripts from these lines. The expression of these repeats was induced by retinoic acid (RA) in cultured ES cells examined by Northern blot analyses. In vivo, their expression was spatially restricted in embryos and in the adult brain as determined by RNA in situ hybridization. We designated this family of sequences as Dr (developmentally regulated) repeats. The members of the Dr family, identified by cDNA cloning and through database search, are highly similar in sequence and show peculiar structural features. Our results suggest the expression of Dr-containing transcripts may be part of an ES cell differentiation program triggered by RA.

Cell autonomous functions of the receptor tyrosine kinase TIE in a late phase of angiogenic capillary growth and endothelial cell survival during murine development

TIE is a receptor tyrosine kinase expressed in both mature endothelial cells and their precursors, as well as in some hematopoietic cells. Mouse embryos homozygous for a disrupted Tie allele die at midgestation due to impaired endothelial cell integrity and resulting hemorrhage. Here we have performed chimeric analysis to study further the function of the murine TIE in the development of embryonic vasculature and in the hematopoietic system. Cells lacking a functional Tie gene (tie(lcz)/tie(lczn-) cells) contributed to the embryonic vasculature at E10.5 as efficiently as cells heterozygous for a targeted Tie allele (tie(lcz)/+ cells). Thus, TIE does not play a significant role in vasculogenesis or in early angiogenic processes, such as formation of the intersomitic arteries and limb bud vascularization. At E15.5 tie(lcz)/tie(lczn-) cells still readily contributed to major blood vessels and to endothelial cells of organs such as lung and heart, which have been suggested to be vascularized by angioblast differentiation. In contrast, the tie(lcz)/tie(lczn-) cells were selected against in the capillary plexuses of several angiogenically vascularized tissues, such as brain and kidney. Our results thus support a role for TIE in late phases of angiogenesis but not vasculogenesis. Furthermore, the results suggest that different mechanisms regulate early and late angiogenesis and provide support for a model of differential organ vascularization by vasculogenic or angiogenic processes. Analysis of adult chimeras suggested that TIE is required to support the survival or proliferation of certain types of endothelial cells demonstrating heterogeneity in the growth/survival factor requirements in various endothelial cell populations. Chimeric analysis of adult hematopoietic cell populations, including peripheral platelets and bone marrow progenitor cells, revealed that tie(lcz)/tie(lczn-) cells were able to contribute to these cell types in a way indistinguishable from tie(lcz)/+ or wild-type cells. Thus, the primary function of TIE appears to be restricted to the endothelial cell lineage.