The ciliary neurotrophic factor and its receptor, CNTFR alpha

Ciliary neurotrophic factor (CNTF) is expressed in glial cells within the central and peripheral nervous systems. CNTF stimulates gene expression, cell survival or differentiation in a variety of neuronal cell types such as sensory, sympathetic, ciliary and motor neurons. In addition, effects of CNTF on oligodendrocytes as well as denervated and intact skeletal muscle have been documented. CNTF itself lacks a classical signal peptide sequence of a secreted protein, but is thought to convey its cytoprotective effects after release from adult glial cells by some mechanism induced by injury. Interestingly, mice that are homozygous for an inactivated CNTF gene develop normally and initially thrive. Only later in adulthood do they exhibit a mild loss of motor neurons with resulting muscle weakness, leading to the suggestion that CNTF is not essential for neural development, but instead acts in response to injury or other stresses. The CNTF receptor complex is most closely related to, and shares subunits with the receptor complexes for interleukin-6 and leukemia inhibitory factor. The specificity conferring alpha subunit of the CNTF complex (CNTFR alpha), is extremely well conserved across species, and has a distribution localized predominantly to the nervous system and skeletal muscle. CNTFR alpha lacks a conventional transmembrane domain and is thought to be anchored to the cell membrane by a glycosyl-phosphatidylinositol linkage. Mice lacking CNTFR alpha die perinatally, perhaps indicating the existence of a second developmentally important CNTF-like ligand. Signal transduction by CNTF requires that it bind first to CNTFR alpha, permitting the recruitment of gp130 and LIFR beta, forming a tripartite receptor complex. CNTF-induced heterodimerization of the beta receptor subunits leads to tyrosine phosphorylation (through constitutively associated JAKs), and the activated receptor provides docking sites for SH2-containing signaling molecules, such as STAT proteins. Activated STATs dimerize and translocate to the nucleus to bind specific DNA sequences, resulting in enhanced transcription of responsive genes. The neuroprotective effects of CNTF have been demonstrated in a number of in vitro cell models as well as in vivo in mutant mouse strains which exhibit motor neuron degeneration. Intracerebral administration of CNTF and CNTF analogs has also been shown to protect striatal output neurons in rodent and primate models of Huntington's disease. Treatment of humans and animals with CNTF is also known to induce weight loss characterized by a preferential loss of body fat. When administered systemically, CNTF activates downstream signaling molecules such as STAT-3 in areas of the hypothalamus which regulate food intake. In addition to its neuronal actions, CNTF and analogs have been shown to act on non-neuronal cells such as glia, hepatocytes, skeletal muscle, embryonic stem cells and bone marrow stromal cells.

A standardized feeding regimen for hypertrophic pyloric stenosis decreases length of hospitalization and hospital costs

BACKGROUND/PURPOSE

Before the institution of a standardized feeding regimen (SFR) for hypertrophic pyloric stenosis (HPS) at the authors' institution, the postoperative feeding regimen and, thus, the length of hospitalization for HPS patients was variable. The aim of this study was to evaluate whether a SFR would affect the length of hospitalization or hospital costs for HPS patients.

METHODS

A 5-year retrospective analysis was performed on 242 patients who underwent pyloromyotomy via a standard right upper quadrant incision. The length of hospitalization and hospital costs were compared in these patients before and after the institution of a standardized postoperative feeding regimen.

RESULTS

The SFR decreased total length of hospitalization by 19.4% (3.1 days v2.5 days, P = .002), postoperative length of stay by 21% (1.9 days v 1.5 days, P< .001), total costs by 11.9% (P= .05), direct costs by 7.7% (P= .22), and indirect costs by 18.6% (P= .003). This occurred despite a small increase in costs per day. The SFR did not change the complication rate (5.3% before SFR v6.1% after SFR, P = 1.0).

CONCLUSION

A postoperative standardized feeding regimen for patients with HPS decreased length of hospitalization and hospital costs without adverse effects.

The urology residency matching program in practice

PURPOSE

We evaluate behaviors and attitudes among resident applicants and program directors related to the American Urological Association (AUA) residency matching program and recommend changes to improve the match.

MATERIALS AND METHODS

Written questionnaires were mailed to 519 resident applicants and 112 program directors after the 1999 American Urological Association match. Subjects were asked about their observations, behaviors and opinions towards the match.

RESULTS

Questionnaires were returned by 230 resident applicants and 94 program directors (44% and 83% response rates, respectively.) Of the resident applicants 75% spent $1,001 to $5,000 for interviewing. Of the program directors 47% recalled that applicants asked how programs would rank the applicant and 61% of applicants recalled that program directors asked applicants how they would rank programs. Dishonesty was acknowledged by 31% of program directors and 44% of resident applicants. Of program directors 82% thought applicants "lied", while 67% of applicants thought that programs "lied" (quotations indicate questionnaire language). Participants characterized their own dishonesty as "just playing the game" or they "did not feel badly." Of program directors 81% and of applicants 61% were "skeptical" or "did not believe" when informed they were a "high" or "number 1" selection. Being asked about marital status was recalled by 91% of male and 100% of female (p = 0. 02), if they had children by 53% of male and 67% of female, (p = 0. 03), and intent to have children by 25% of male and 62% of female (p <0.001), applicants, respectively. Free-form comments were written by 132 resident applicants and 28 program directors. The most frequent comments suggested the need to improve ethical behavior, modify the process so applications could be transmitted electronically and modify interviews to reduce applicant financial burden. Nine female applicants commented on their perceptions of sexual discrimination during the interviews.

CONCLUSIONS

Resident applicants and program directors violate match code rules frequently. Program directors and resident applicants are skeptical of each other. Patterns of faculty behavior differ based on applicant gender. Interviews are costly for applicants. We recommend that 1) programs adopt policies to enhance fairness, 2) applications be filed electronically, 3) programs assist resident applicants with interview accommodation to reduce financial burden and 4) a post-interview code of limited or noncommunication be adopted.

Recruitment behavior and program directors: how ethical are their perspectives about the match process?

OBJECTIVE

This study examined family practice residency directors' perspectives on the 1999 National Resident Matching Program (NRMP) process and identified directors' expectations for students' recruitment behavior.

METHODS

Subjects were the family practice residency program directors. A 22-item written questionnaire was mailed to each director. The questions related to the directors' perceptions of the following issues: applicants interviewing in more than one specialty, communication initiated by programs or applicants, commitments made to applicants and by applicants, ethical dilemmas faced by the program director, and the NRMP process itself. Descriptive statistics were reported.

RESULTS

Only a few of the residency program directors (9.1%) felt that it was ethically wrong for an applicant to interview in more than one specialty. However, most program directors (83%) indicated that the knowledge of an applicant interviewing in more than one specialty had a "significant" negative or "some" negative effect on the applicant's rank order. Ninety-five percent of program directors indicated that they engage in follow-up communication with applicants following the formal interview. Almost all program directors (98%) reported that at least some applicants contact them following the formal interview to inform them that the program was a "high" or No. 1 rank-order choice. The majority of program directors (94%) felt that the NRMP process placed their program in the position of having to be dishonest with applicants to match their top choices.

CONCLUSIONS

The results of the study indicate that the actions of many program directors and applicants may not be consistent with the written policies of the NRMP.

The molecular basis of lung morphogenesis

To form a diffusible interface large enough to conduct respiratory gas exchange with the circulation, the lung endoderm undergoes extensive branching morphogenesis and alveolization, coupled with angiogenesis and vasculogenesis. It is becoming clear that many of the key factors determining the process of branching morphogenesis, particularly of the respiratory organs, are highly conserved through evolution. Synthesis of information from null mutations in Drosophila and mouse indicates that members of the sonic hedgehog/patched/smoothened/Gli/FGF/FGFR/sprouty pathway are functionally conserved and extremely important in determining respiratory organogenesis through mesenchymal-epithelial inductive signaling, which induces epithelial proliferation, chemotaxis and organ-specific gene expression. Transcriptional factors including Nkx2.1, HNF family forkhead homologues, GATA family zinc finger factors, pou and hox, helix-loop-helix (HLH) factors, Id factors, glucocorticoid and retinoic acid receptors mediate and integrate the developmental genetic instruction of lung morphogenesis and cell lineage determination. Signaling by the IGF, EGF and TGF-beta/BMP pathways, extracellular matrix components and integrin signaling pathways also directs lung morphogenesis as well as proximo-distal lung epithelial cell lineage differentiation. Soluble factors secreted by lung mesenchyme comprise a 'compleat' inducer of lung morphogenesis. In general, peptide growth factors signaling through cognate receptors with tyrosine kinase intracellular signaling domains such as FGFR, EGFR, IGFR, PDGFR and c-met stimulate lung morphogenesis. On the other hand, cognate receptors with serine/threonine kinase intracellular signaling domains, such as the TGF-beta receptor family are inhibitory, although BMP4 and BMPR also play key inductive roles. Pulmonary neuroendocrine cells differentiate earliest in gestation from among multipotential lung epithelial cells. MASH1 null mutant mice do not develop PNE cells. Proximal and distal airway epithelial phenotypes differentiate under distinct transcriptional control mechanisms. It is becoming clear that angiogenesis and vasculogenesis of the pulmonary circulation and capillary network are closely linked with and may be necessary for lung epithelial morphogenesis. Like epithelial morphogenesis, pulmonary vascularization is subject to a fine balance between positive and negative factors. Angiogenic and vasculogenic factors include VEGF, which signals through cognate receptors flk and flt, while novel anti-angiogenic factors include EMAP II.

The ciliary neurotrophic factor and its receptor, CNTFR alpha

Ciliary neurotrophic factor (CNTF) is expressed in glial cells within the central and peripheral nervous systems. CNTF stimulates gene expression, cell survival or differentiation in a variety of neuronal cell types such as sensory, sympathetic, ciliary and motor neurons. In addition, effects of CNTF on oligodendrocytes as well as denervated and intact skeletal muscle have been documented. CNTF itself lacks a classical signal peptide sequence of a secreted protein, but is thought to convey its cytoprotective effects after release from adult glial cells by some mechanism induced by injury. Interestingly, mice that are homozygous for an inactivated CNTF gene develop normally and initially thrive. Only later in adulthood do they exhibit a mild loss of motor neurons with resulting muscle weakness, leading to the suggestion that CNTF is not essential for neural development, but instead acts in response to injury or other stresses. The CNTF receptor complex is most closely related to, and shares subunits with the receptor complexes for interleukin-6 and leukemia inhibitory factor. The specificity conferring alpha subunit of the CNTF complex (CNTFR alpha), is extremely well conserved across species, and has a distribution localized predominantly to the nervous system and skeletal muscle. CNTFR alpha lacks a conventional transmembrane domain and is thought to be anchored to the cell membrane by a glycosyl-phosphatidylinositol linkage. Mice lacking CNTFR alpha die perinatally, perhaps indicating the existence of a second developmentally important CNTF-like ligand. Signal transduction by CNTF requires that it bind first to CNTFR alpha, permitting the recruitment of gp130 and LIFR beta, forming a tripartite receptor complex. CNTF-induced heterodimerization of the beta receptor subunits leads to tyrosine phosphorylation (through constitutively associated JAKs), and the activated receptor provides docking sites for SH2-containing signaling molecules, such as STAT proteins. Activated STATs dimerize and translocate to the nucleus to bind specific DNA sequences, resulting in enhanced transcription of responsive genes. The neuroprotective effects of CNTF have been demonstrated in a number of in vitro cell models as well as in vivo in mutant mouse strains which exhibit motor neuron degeneration. Intracerebral administration of CNTF and CNTF analogs has also been shown to protect striatal output neurons in rodent and primate models of Huntington's disease. Treatment of humans and animals with CNTF is also known to induce weight loss characterized by a preferential loss of body fat. When administered systemically, CNTF activates downstream signaling molecules such as STAT-3 in areas of the hypothalamus which regulate food intake. In addition to its neuronal actions, CNTF and analogs have been shown to act on non-neuronal cells such as glia, hepatocytes, skeletal muscle, embryonic stem cells and bone marrow stromal cells.

Feeling the stress: perceptions of burnout among general surgery program directors

PURPOSE

To document the types and levels of stress experienced by general surgery program directors as they fulfill their education and administrative responsibilities.

METHODS

This study consisted of a 3-part survey that incorporated 2 established instruments to help determine the presence of burnout in program directors. A personal projects analysis was used to help identify the tasks most relevant to the role of program director as well as to evaluate their perceptions of these tasks. The Maslach Burnout Inventory (MBI) was used to measure the degree of burnout among program directors. Demographic data were gathered to develop a picture of the background of the program directors and how they spent their time.

RESULTS

A total of 71.8% of program directors responded. Of all tasks, teaching received the highest ratings for importance, enjoyment, and control, as well as the lowest ratings for stress. Emotional exhaustion was the most notable aspect of burnout in program directors on the MBI. Program directors scoring high in burnout were younger, had been in their current position fewer years, and had fewer years overall as a program director.

CONCLUSIONS

Burnout is more related to age and experience of program director than to features of the program itself.

Venous ischemia as a cause of ureteral necrosis in transplanted ureters

BACKGROUND

Urologic complications after pediatric renal transplantation can adversely effect the outcome and may result in decreased graft survival. Efforts to prevent these complications are worthwhile. This study investigates the incidence of these complications in a clinical transplant program and reports on an animal model used to investigate one possible cause.

METHODS

In the clinical study, the results of a pediatric renal transplant program at a large children's hospital for a 5(1/2)-year period were reviewed with special attention paid to patients suffering ureteral necrosis. In the experimental study, 9 swine underwent laparotomy, bilateral complete infrahilar ureteric dissection, and extravesical ureteroneocystostomy. On the left side only, the renal and adrenal veins were ligated. The arterial supply remained intact. The right side did not undergo vessel ligation and served as the control. Three pigs each were killed at 3, 8, and 15 days. Kidneys, ureters and a cuff of bladder were examined histologically.

RESULTS

In the clinical study 75 renal transplants were performed with a total of 5 cases of early ureteral necrosis. Two of these 5 displayed venous congestion and ischemia, and 2 were associated with kidneys displaying primary nonfunction of the graft. Seventy-one of 75 grafts are continuing to function. One of the 4 early graft losses also had an ischemic ureter. In the experimental study all right kidneys and ureters were normal. All left kidneys had complete hemorrhagic necrosis. Necrosis also was found in 5 of 9 proximal left ureters and in 7 of 9 distal left ureters. Viable left ureters displayed moderate to severe submucosal and periureteric hemorrhage. Four of 9 ureters displayed more damage distally than proximally. The extent of necrosis was similar at 3, 8, and 15 days.

CONCLUSION

In both clinical and experimental studies, venous congestion and subsequent ischemia have been shown to be important causes of ureteral necrosis after renal transplantation.

The umbilical fold approach to pyloromyotomy: is it a safe alternative to the right upper-quadrant approach?

BACKGROUND

Hypertrophic pyloric stenosis has been approached using two standard incisions for pyloromyotomy: the circumumbilical (UMB) and the right upper quadrant (RUQ). The UMB approach produces an almost undetectable scar but has been associated with more complications.

STUDY DESIGN

A 5-year retrospective analysis was performed on 344 patients (90 UMB and 254 RUQ) to compare technical and wound complications. The effect of prophylactic antibiotics on wound infection was also evaluated.

RESULTS

The intraoperative complication rate was 5.5% (13.3% UMB versus 2.8% RUQ; p = 0.001). The mucosal perforation rate was 3.5% (8.9% UMB versus 1.6% RUQ; p = 0.003). Mucosal perforations increased the mean +/- SD length of hospitalization in UMB patients (3.9 +/- 0.8 versus 2.4 +/- 1.1 days; p < 0.001). The serosal tear rate was 2.0% (4.4% UMB versus 1.2% RUQ; p=0.08). The postoperative complication rate was 5.8% (14.4% UMB versus 2.8% RUQ; p < 0.001), and the wound infection rate was 2.6% (6.7% UMB versus 1.2% RUQ; p = 0.01). Antibiotic prophylaxis decreased the rate of wound infection to 1.8% and eliminated the statistical difference between the groups (4.5% UMB versus 0% RUQ; p=0.16). The rate of other postoperative complications was 3.2% (7.8% UMB versus 1.6% RUQ; p = 0.009). Duration of hospital stay did not differ between the groups overall (2.6+/-1.12 days for UMB versus 2.7+/-1.5 days for RUQ; p = 0.35).

CONCLUSIONS

The UMB approach to pyloromyotomy was cosmetically superior but increased complication rates. Technical complications were easily corrected and length of stay was not affected. Wound infections were decreased in both groups by the use of prophylactic antibiotics.

Abrogation of cyclin D1 expression predisposes lung cancer cells to serum deprivation-induced apoptosis

Cyclin D1 antisense (D1AS)-transfected lung epithelial cell lines were serum deprived and then analyzed for three hallmarks of apoptosis: appearance of single-strand DNA breaks, alteration of apoptosis-related protein expression, and induction of chromatin condensation. Single-strand DNA breaks appeared at significant levels 24 h after serum deprivation, whereas induction of chromatin condensation was observed after 72 h. The antioxidants dimethyl sulfoxide, ascorbate, and glutathione, as well as insulin-like growth factor-I, inhibited induction of DNA damage in this assay. Additionally, proliferating cell nuclear antigen expression is completely suppressed in the D1AS cells, indicating a mechanism to explain the reduced capacity for DNA repair. Increased expression of cyclin D1, which is a common lesion in lung cancer, may thus prevent induction of apoptosis in an oxidizing and growth factor-poor environment. Reducing cyclin D1 expression in lung cancer cells by expression of D1AS RNA disrupted these protective pathways.

Is match ethics an oxymoron?

BACKGROUND

Graduate medical education has undergone economic and structural changes-changes that have placed increasing pressure on medical students and programs to match effectively. This study documents the experiences, perceptions, and ethical dilemmas of medical students with the 1998 match process.

METHODS

Surveyed were 437 senior students from three medical schools. Students were questioned about: interviewing practices, communication with programs, commitments made, ethical dilemmas faced, and the match process itself. Data were analyzed using Student's t test, the chi-square test, and descriptive statistics.

RESULTS

In all, 314 (72%) students responded. Programs expect postinterview communication from students (57%). Students perceive that programs are making "informal" commitments (43%), lying to them (33%), and encouraging their unethical behavior in order to match (21%). Ethical dilemmas are related to requests for informal commitments.

CONCLUSIONS

The NRMP's ruling that denounces prematch commitments is being broken by students and programs alike, resulting in the promotion of unprofessional behavior and gamesmanship.

Apoptosis and DNA damage in type 2 alveolar epithelial cells cultured from hyperoxic rats

Apoptosis is a genetically controlled cellular response to developmental stimuli and environmental insult that culminates in cell death. Sublethal hyperoxic injury in rodents is characterized by a complex but reproducible pattern of lung injury and repair during which the alveolar surface is damaged, denuded, and finally repopulated by type 2 alveolar epithelial cells (AEC2). Postulating that apoptosis might occur in AEC2 after hyperoxic injury, we looked for the hallmarks of apoptosis in AEC2 from hyperoxic rats. A pattern of increased DNA end labeling, DNA laddering, and induction of p53, p21, and Bax proteins, strongly suggestive of apoptosis, was seen in AEC2 cultured from hyperoxic rats when compared with control AEC2. In contrast, significant apoptosis was not detected in freshly isolated AEC2 from oxygen-treated rats. Thus the basal culture conditions appeared to be insufficient to ensure the ex vivo survival of AEC2 damaged in vivo. The oxygen-induced DNA strand breaks were blocked by the addition of 20 ng/ml of keratinocyte growth factor (KGF) to the culture medium from the time of plating and were partly inhibited by Matrigel or a soluble extract of Matrigel. KGF treatment resulted in a partial reduction in the expression of the p21, p53, and Bax proteins but had no effect on DNA laddering. We conclude that sublethal doses of oxygen in vivo cause damage to AEC2, resulting in apoptosis in ex vivo culture, and that KGF can reduce the oxygen-induced DNA damage. We speculate that KGF plays a role as a survival factor in AEC2 by limiting apoptosis in the lung after acute hyperoxic injury.

Inhibition of vascular and epithelial differentiation in murine nitrofen-induced diaphragmatic hernia

Neonates with congenital diaphragmatic hernia (DH) die of pulmonary hypoplasia and persistent pulmonary hypertension. We used immunohistochemical localization of alpha-smooth muscle actin (alpha-SMA), platelet endothelial cell adhesion molecule (PECAM)-1, thyroid transcription factor (TTF)-1, surfactant protein (SP) A, SP-C, and competitive RT-PCR quantitation of TTF-1, SP-A, SP-C, and alpha-SMA mRNA expression to characterize the epithelial and vascular phenotype of lungs from ICR fetal mice with a nitrofen-induced DH. Nitrofen (25 mg) was gavage fed to pregnant mice on day 8 of gestation. Fetal mice were delivered on day 17. The diaphragm was examined for a defect, and the lungs were either fixed, sectioned, and immunostained or processed for mRNA isolation. In comparison with control lungs, DH lungs showed increased expression of alpha-SMA mRNA, fewer and more muscular arterioles (alpha-SMA), less well-developed capillary networks (PECAM-1), delayed epithelial development marked by a persistence of TTF-1 in the periphery, and decreased SP-A mRNA and SP-A expression. These data suggest that in the murine nitrofen-induced DH, as in human congenital DH, pulmonary insufficiency is due to an inhibition of peripheral pulmonary development including terminal airway and vascular morphogenesis.

Contractility, transforming growth factor-beta, and plasmin in fetal skin fibroblasts: role in scarless wound healing

The early fetus responds to cutaneous wounds in a fundamentally different way from the adult; fetal wounds heal without scars. Wound contraction is a vital component of wound healing. The cytokine transforming growth factor (TGF)-beta promotes wound contraction and can be activated by the serine protease plasmin. Herein, we explored whether murine skin fibroblast contractile properties, TGF-beta, and plasmin formation are developmentally regulated. Our results showed that early fetal mouse embryonic day 15 skin fibroblasts contracted a collagen gel less, secreted less active and total TGF-beta, and generated less plasmin than either late fetal (embryonic day 17) or adult skin fibroblasts. Furthermore, there was a slight positive correlation between the formation of plasmin and the level of activation of TGF-beta. We conclude that early fetal mouse skin fibroblasts contract a collagen gel and secrete and activate TGF-beta to a lesser extent than do late fetal and adult skin fibroblasts. We speculate that the fetal skin fibroblast undergoes a developmental transition that causes wounds in mouse to contract at or after embryonic day 17. Further, this developmental transition is influenced by growth factor-fibroblast interactions and coincides with the emergence of the skin fibroblast's ability to generate plasmin and activate TGF-beta.

Relative resistance of striatal neurons containing calbindin or parvalbumin to quinolinic acid-mediated excitotoxicity compared to other striatal neuron types

To evaluate the relative ability of those striatal neuron types containing calbindin or parvalbumin to withstand a Ca(2+)-mediated excitotoxic insult, we injected the NMDA receptor-specific excitotoxin quinolinic acid (QA) into the striatum in mature adult rats and 2 months later examined the relative survival of striatal interneurons rich in parvalbumin and striatal projection neurons rich in calbindin. To provide standardization to the survival of striatal neuron types thought to be poor in Ca2+ buffering proteins, the survival was compared to that of somatostatin-neuropeptide Y (SS/NPY)-containing interneurons and enkephalinergic projection neurons, which are devoid of or relatively poorer in such proteins. The various neuron types were identified by immunohistochemical labeling for these type-specific markers and their relative survival was compared at each of a series of increasing distances from the injection center. In brief, we found that parvalbuminergic, calbindinergic, and enkephalinergic neurons all showed a generally comparable gradient of neuronal loss, except just outside the lesion center, where calbindin-rich neurons showed significantly enhanced survival. In contrast, striatal SS/NPY interneurons were more vulnerable to QA than any of these three other types. These observed patterns of survival following intrastriatal QA injection suggest that calbindin and parvalbumin content does not by itself determine the vulnerability of striatal neurons to QA-mediated excitotoxicity in mature adult rats. For example, parvalbuminergic striatal interneurons were not impervious to QA, while cholinergic striatal interneurons are highly resistant and SS/NPY+ striatal interneurons are highly vulnerable. Both cholinergic and SS/NPY+ interneurons are devoid of any known calcium buffering protein. Similarly, calbindin does not prevent striatal projection neuron vulnerability to QA excitotoxicity. Nonetheless, our data do suggest that calbindin may offer striatal neurons some protection against moderate excitotoxic insults, and this may explain the reportedly slightly greater vulnerability of striatal neurons that are poor in calbindin to ischemia and Huntington's disease.

Cyclin D1 antisense RNA destabilizes pRb and retards lung cancer cell growth

To investigate the role of cyclin D1 in the regulation of lung cancer cell growth, we created five stably transfected cell lines carrying a cyclin D1 antisense construct. The transfected cells exhibited a marked decrease in the rate of cell growth, in contrast to the original lines (A549 and NCI-H441). The expression of several cell cycle-regulating proteins, including cyclin A, the cyclin-dependent kinases (cdk) 2 and cdk4, in addition to cyclin D1 itself, was markedly decreased. The expression of one cdk inhibitor, p21WAF1/CIP1, increased in the A549-derived cell lines. A specific target of cyclin D1 activity, the growth-suppressing product of the retinoblastoma gene, pRb, exhibited decreased expression and a decreased level of phosphorylation in the transfected cells. Decreased expression of pRb due to a significant increase in its turnover rate suggested that the stability of the protein may depend on phosphorylation by cyclin D1-dependent cdk activity. In addition to the impact on pRb stability, decreased expression of cyclin D1 induced susceptibility to cell death after withdrawal of exogenous growth factors in the antisense transfected cell lines, a response that was not observed in the original cancer cell lines. We conclude that abrogation of cyclin D1 overexpression in lung cancer cells disrupts several key pathways that are required for uncontrolled cell growth and induces those that lead to cell death after growth factor deprivation. Therefore, we speculate that use of antisense cyclin D1 expression in appropriate gene vectors could be a useful method for retarding lung cancer cell growth in accessible tumors such as those of the lung epithelium.

Cell cycle in alveolar epithelial type II cells: integration of Matrigel and KGF

The regulation of cell cycle control in alveolar epithelial type II cells (AEC2) in response to peptide growth factors and extracellular matrix signals is not well understood. Herein, we have determined that, in adult rat AEC2 in primary culture on Engelbreth-Holm-Swarm biomatrix (Matrigel) in the presence of keratinocyte growth factor, the expression of key cell cycle control elements, including cyclins A and D and cyclin-dependent kinases (cdk) 1 and 4, is increased and that retinoblastoma protein (pRb) phosphorylation is also increased, with a corresponding decrease in the expression of p53 and the cdk inhibitors (cdkis) p21WAF1/CIP1 and p27KIP-1 compared with cells cultured on plastic. The Matrigel biomatrix-KGF culture conditions were also associated with an enhanced proliferative response, as measured by fluorescent-activated cell sorter analysis, thymidine incorporation into DNA, and proliferating cell nuclear antigen expression. This enhanced proliferation occurred with neither a soluble extract of Matrigel biomatrix nor with other simple biological matrices. We conclude that coordinated induction of key cyclins and cdks, with the concomitant suppression of key negative cell cycle regulators, occurs in AEC2 on Matrigel biomatrix in the presence of KGF. We speculate that the balance between cyclin and cdk activation and cdki suppression in AEC2 serves to integrate the combined influences of biomatrix and KGF signaling on pRb phosphorylation, thereby controlling transit through S phase of the cell cycle. Conversely, AEC2 express high levels of cdkis and p53 at rest in G1 phase. The latter finding may explain the quiescent state of normal adult AEC2 in vivo.

Factor VII C329R: a variant with a disrupted disulfide bond in the catalytic domain

We report a novel mutation within the coagulation factor VII gene associated with a dysfunctional procoagulant factor VII (12% of normal plasma factor VII activity; 50% of normal plasma factor VII antigen level). Using heteroduplex analysis and subsequent sequencing, we identified a thymine-10,902 to cytosine mutation within exon eight of the factor VII gene, encoding for a substitution of arginine for cysteine-329 (factor VII C329R) within the heavy chain of factor VII. This substitution disrupts a disulfide bond within the factor VII catalytic domain and might cause altered conformation of the active site triad.

Characterization of a full-length cDNA for rabbit factor X

A 300 bp probe generated by the PCR was derived from rabbit genomic DNA using primers from a highly conserved region of the DNA for human factor X (HFX). The probe was used in northern blot analysis of liver RNA to demonstrate an mRNA species of 1.6 kb for the rabbit factor X and subsequently for isolation and characterization of the cDNA for rabbit factor X (RFX) from a lambda Zap II cDNA library generated from rabbit liver mRNA. The cDNA contains 22 bases upstream from the 5'-translation initiation codon, 1470 nucleotides of open reading frame, a stop codon and a 3' poly (A) tail. The cDNA codes for a 40-residue signal/propeptide region, followed by a 447-residue mature protein. The deduced amino acid sequence shows a high degree of homology with the sequence of HFX. Inhibitory peptides derived from interactive sites of HFX for activators, cofactor and substrate exerted degrees of inhibition of RFX activation which showed a dependence on extent of homology with the corresponding regions of RFX.

Can continuity-of-care requirements for surgery residents be demonstrated in the current teaching environment?

In 1994, the Residency Review Committee in Surgery began evaluating the ability of programs to provide adequate continuity-of-care experiences to residents, based on 6 criteria requiring resident participation in each phase of a surgical patient's care. The Residency Review Committee document further described resident and patient experiences as being synonymous. No previous studies were found that examined the 6 criteria or compared them with the patient's experience with continuity. Study objectives were 2-fold: (1) to assess the 6 required continuity-of-care experiences provided to general surgery residents and (2) to compare resident experiences to the patient's experience with continuity. Surgery residents from 2 academic years, representing each postgraduate year, were studied. Patients had (1) undergone an operation involving a resident and (2) remained hospitalized for longer than 24 hours but less than 10 days. Data were collected from a retrospective randomized review of each patient's medical records. Of the 114 cases, 23.7% showed that the same resident participated in all phases of care. In the remaining cases, residents provided preoperative care in 70.2%, directed the postoperative hospitalized care in 86.8%, and provided postdischarge care in 37.7%. Patients saw an average +/- SD of 4.6 +/- 1.5 surgical providers during the entire course of their surgical care. In conclusion, continuity experiences were provided to surgery residents in varying quantities and combinations, with one quarter of the residents experiencing "perfect continuity." Resident continuity experiences and patient continuity were not synonymous. Although improved medical record documentation may have enhanced these results, continuity-of-care remains difficult to demonstrate in view of the current surgery teaching environment.

Ciliary neurotrophic factor protects striatal output neurons in an animal model of Huntington disease

Huntington disease is a dominantly inherited, untreatable neurological disorder featuring a progressive loss of striatal output neurons that results in dyskinesia, cognitive decline, and, ultimately, death. Neurotrophic factors have recently been shown to be protective in several animal models of neurodegenerative disease, raising the possibility that such substances might also sustain the survival of compromised striatal output neurons. We determined whether intracerebral administration of brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3, or ciliary neurotrophic factor could protect striatal output neurons in a rodent model of Huntington disease. Whereas treatment with brain-derived neurotrophic factor, nerve growth factor, or neurotrophin-3 provided no protection of striatal output neurons from death induced by intrastriatal injection of quinolinic acid, an N-methyl-D-aspartate glutamate receptor agonist, treatment with ciliary neurotrophic factor afforded marked protection against this neurodegenerative insult.

Light and electron microscopic immunohistochemical study of dopaminergic terminals in the striatal portion of the pigeon basal ganglia using antisera against tyrosine hydroxylase and dopamine

A dopaminergic projection from the midbrain to the striatal portion of the basal ganglia is present in reptiles, birds, and mammals. Although the ultrastructure of these fibers and terminals within the striatum has been studied extensively in mammals, little information is available on the ultrastructure of this projection in nonmammals. In the present study, we used immunohistochemical labeling with antibodies against tyrosine hydroxylase (TH) or dopamine (DA) to study the dopaminergic input to the striatal portion of the basal ganglia in pigeons (i.e., lobus parolfactorius and paleostriatum augmentatum). At the light microscopic level, the anti-TH and anti-DA revealed a similar abundance and distribution of numerous labeled fine fibers and varicosities within the striatum. In contrast, the use of an antidopamine beta-hydroxylase antiserum (which labels only adrenergic and noradrenergic terminals) labeled very few striatal fibers, which were restricted to visceral striatum. These results demonstrate that anti-TH mainly labels dopaminergic terminals in the striatum. At the electron microscopic level, the anti-TH and anti-DA antisera labeled numerous axon terminals within the striatum (15-20% of all striatal terminals). These terminals tended to be small (with an average length of 0.6 microns) and flattened, and their vesicles tended to be small (35-60 nm in diameter) and pleomorphic. About 50% of the terminals were observed to make synaptic contacts in the planes of section examined, and nearly all of these synaptic contacts were symmetric. Both TH+ and DA+ terminals typically contacted dendritic shafts or the necks of dendritic spines, but a few contacted perikarya. No clear differences were observed between TH+ and DA+ terminals within medial striatum (whose neurons project to the nigra in birds) or between TH+ and DA+ terminals within lateral striatum (whose neurons project to the pallidum in birds). In addition, no differences were observed between medial and lateral striata in either TH+ or DA+ terminals. Thus, there is no evident difference in pigeons between striatonigral and striatopallidal neurons in their dopaminergic innervation. Our results also indicate that the abundance, ultrastructural characteristics, and postsynaptic targets of the midbrain dopaminergic input to the pigeon striatum are highly similar to those in mammals. This anatomical similarity is consistent with the pharmacologically demonstrable similarity in the role of the dopaminergic input to the striatum in birds and mammals.

Neurotrophin-4/5 maintains the cholinergic phenotype of axotomized septal neurons

We examined the effect of intraseptal or intracerebroventricular (i.c. v.) infusions of NT-4/5 or intraseptal infusions of NGF on the level of immunohistochemical staining of choline acetyltransferase (ChAT)and the low-affinity nerve growth factor receptor (LNGFR)in the rat medial septum following unilateral transection of the fimbria. The extent of cell loss in the septum ipsilateral to the lesion, determined by cell counts of ChAT-immunopositive neurons and expressed as a ratio comparing the lesioned to the intact sides, was 0.28 in animals that received an infusion of phosphate-buffered saline (PBS). The ratios were 0.97 and 1.07 in animals that received an infusion of NT-4/5 into the ipsilateral ventricle and septum respectively. Septal infusions of NGF produced a ratio of ChAT-immunopositive cells of 1.03. The ratios of LNGFR-immunopositive neurons increased from 0.50 in PBS-infused animals to 0.79 and 0.83 in animals infused with NT-4/5 via the i.c. v. infusion of NT-4/5 or septal infusion of NT-4/5 or NGF. As determined by immunohistochemical staining, NT-4/5 infused into the lateral ventricle was detected in the periventricular portions of the forebrain ipsilateral to the infusion, while NT-4/5 or NGF infused intraseptally was detected in much of the septum, bilaterally. Furthermore, exogenous NT-4/5 or NGF was detected in numerous neuronal perikarya in the medial septal and diagonal band nuclei. These data demonstrate that, as with NGF, i.c.v. as well as septal infusions of NT-4/5 can maintain the phenotype of basal forebrain cholinergic neurons following axotomy.

An ultrastructural double-label immunohistochemical study of the enkephalinergic input to dopaminergic neurons of the substantia nigra in pigeons

Electron microscopic immunohistochemical double-label studies were carried out in pigeons to characterize the ultrastructural organization and postsynaptic targets of enkephalinergic (ENK+) striatonigral projection. ENK+ terminals in the substantia nigra were labeled with antileucine-enkephalin antiserum by using peroxidase-antiperoxidase methods, and dopaminergic neurons were labeled with anti-tyrosine hydroxylase antiserum by using silver-intensified immunogold methods. ENK+ terminals on dopaminergic neurons were equal in abundance to ENK+ terminals on nondopaminergic neurons, although the former were typically somewhat smaller than the latter (mean size: 0.50 vs. 0.75 micron, respectively). ENK+ terminals were evenly distributed on the cell bodies and dendrites of dopaminergic neurons, and they were evenly distributed on dendrites but rare on perikarya of nondopaminergic neurons. Transection of the basal telencephalic output revealed that 75% of the nigral ENK+ terminals were of basal telencephalic origin. These telencephalic ENK+ terminals included over 80% of those smaller than 0.80 micron on dopaminergic neurons and smaller than 1.0 micron on nondopaminergic neurons, and none greater than this in size. Both telencephalic and the nontelencephalic ENK+ nigral terminals made predominantly symmetric synapses on nigral neurons. Although the basal telencephalic ENK+ terminals uniformly targeted dendrites and perikarya, nontelencephalic ENK+ terminals seemed to avoid perikarya. The results indicate that ENK+ striatonigral neurons in birds may directly influence both dopaminergic and nondopaminergic neurons of the substantia nigra. Based on similar data for substance P-containing striatonigral terminals, the roles of enkephalin and substance P in influencing nigral dopaminergic neurons may differ slightly, as they appear to target preferentially different portions of dopaminergic neurons. The overall results in pigeons are similar to those for ENK+ terminals in the ventral tegmental area in rats, suggesting that the synaptic organization of the ENK+ input to the tegmental dopaminergic cell fields is similar in mammals and birds.