Biomedical subjects

E Skolnik

Publications and source records attributed to E Skolnik.

14 recordsLinked to original sources

PubMed1993

Guanine-nucleotide-releasing factor hSos1 binds to Grb2 and links receptor tyrosine kinases to Ras signalling.

Many of the actions of receptor tyrosine kinases are mediated by the protein Ras, including the activation of various downstream serine/threonine kinases and the stimulation of growth and differentiation. The human protein Grb2 binds to ligand-activated growth factor receptors and downstream effector proteins through its Src-homology (SH) domains SH2 and SH3, respectively, and like its homologue from Caenorhabditis elegans, Sem-5, apparently forms part of a highly conserved pathway by which these receptors can control Ras activity. Here we show that the SH3 domains of Grb2 bind to the carboxy-terminal part of hSos1, the human homologue of the Drosophila guanine-nucleotide-releasing factor for Ras, which is essential for control of Ras activity by epidermal growth factor receptor and sevenless. Moreover, a synthetic 10-amino-acid peptide containing the sequence PPVPPR specifically blocks the interaction. These results indicate that the Grb2/hSos1 complex couples activated EGF receptor to Ras signalling.

3T3 Cells↗

PubMed1992

High-efficiency expression/cloning of epidermal growth factor-receptor-binding proteins with Src homology 2 domains.

Src homology 2 domains bind to tyrosine-phosphorylated growth factor receptors and are found in proteins that serve as substrates for tyrosine kinases, such as phospholipase C-gamma 1 and ras GTPase-activating protein. We have previously described the cloning of phosphatidylinositol 3'-kinase-associated p85 from expression libraries with the tyrosine-phosphorylated epidermal growth factor receptor as a probe. We have now modified this technique by using T7 polymerase-based expression libraries, which significantly improves sensitivity of the method. In one screening of such a library, we identified five different murine Src homology 2 domain-containing proteins, which we call GRBs (growth factor receptor-bound proteins). Two of these proteins represented the tyrosine kinase fyn and the mouse homologue of phospholipase C-gamma 1, whereas two genes encoded proteins similar to v-crk and NCK. We also isolated the gene for GRB-7, which encodes a protein of 535 amino acids. In addition to a Src homology 2 domain, GRB-7 also has a region of similarity to the noncatalytic domain of ras GTPase-activating protein and is highly expressed in liver and kidney. Use of this expression/cloning system should increase our ability to identify downstream modulators of growth factor action.

Amino Acid Sequence↗

PubMed1991

Advanced glycosylation end products in patients with diabetic nephropathy.

BACKGROUND: Glucose reacts nonenzymatically with proteins in vivo, chemically forming covalently attached glucose-addition products and cross-links between proteins. The excessive accumulation of rearranged late-glucose-addition products, or advanced glycosylation end products (AGEs), is believed to contribute to the chronic complications of diabetes mellitus. METHODS: To elucidate the relation of AGEs to diabetic complications, we used a radioreceptor assay to measure serum and tissue AGEs in diabetic (Types I and Type II) and nondiabetic patients with different levels of renal function. Serum AGEs were measured as a low-molecular-weight (less than or equal to 10 kd) peptide fraction and a high-molecular-weight (greater than 10 kd) protein fraction. RESULTS: The mean (+/- SD) AGE content of samples of arterial-wall collagen from 9 diabetic patients was significantly higher than that of samples from 18 nondiabetic patients (14.5 +/- 5.2 vs. 3.6 +/- 1.5 AGE units per milligram, P less than 0.001). Moreover, diabetic patients with end-stage renal disease had almost twice as much AGE in tissue as diabetic patients without renal disease (21.3 +/- 2.8 vs. 11.5 +/- 1.9 AGE units per milligram, P less than 0.001). The AGE levels in both serum fractions were elevated in the patients with diabetes, and the levels of AGE peptides correlated directly with serum creatinine (P less than 0.001) and inversely with creatinine clearance (P less than 0.005), suggesting that levels of AGE peptides increased with the severity of diabetic nephropathy. In six patients with diabetes who required hemodialysis, the levels of AGE peptides were five times higher than in eight normal subjects (82.8 +/- 9.4 vs. 15.6 +/- 3.4 AGE units per milliliter, P less than 0.001). In another group of diabetic patients the mean serum creatinine level, which decreased by 75 percent during a session of hemodialysis, whereas the level of AGE peptides decreased by only 24 percent. Serum levels of AGE peptides were normal in two patients with normal serum creatinine levels after renal transplantation. CONCLUSIONS: AGEs accumulate at a faster-than-normal rate in arteries and the circulation of patients with diabetes; the increase in circulating AGE peptides parallels the severity of renal functional impairment in diabetic nephropathy.

Adult↗

PubMed1990

A novel addition to the T cell repertory. Cell surface expression of tumor necrosis factor/cachectin by activated normal human T cells.

Expression of the pluripotent molecule TNF in a focused and antigen-restricted fashion might provide an advantage to the host organism. Given the central role of T cells in antigen-specific immunity, we examined whether activated T cells express TNF on their cell surface. FACS analysis of highly purified normal human T cells labeled with an anti-TNF mAb revealed that T cells express cell surface TNF when signaled with the synergistic combination of a calcium ionophore, ionomycin, and a protein kinase C activator, 12-o-tetradecanoyl phorbol acetate. Cell surface radioiodination studies of stimulated T cells demonstrated the presence of 26-kD transmembrane protein, a size predicted by TNF cDNA and different from that of the 17-kD secreted TNF molecule. The induced cell surface expression of TNF could be blocked with cyclosporine and/or methylprednisolone, and Northern analysis for TNF-specific transcripts revealed that this inhibitory effect occurs pretranslationally. Our demonstration for the first time that stimulated normal human T cells display cell surface TNF provides a mechanistic basis for the realization of effects of TNF in an antigen-specific fashion.

Cyclosporins↗

PubMed1990

Physiologic signaling in normal human T-cells: mRNA phenotyping by northern blot analysis and reverse transcription-polymerase chain reaction.

Synergy between ionomycin and sn-1,2-dioctanoylglycerol (diC8) was shown at the level of lymphokine gene transcription. Transcriptional activation of interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and the protooncogene H-ras was accomplished by signaling highly purified normal human resting T-lymphocytes (T-cells) with diC8, a physiologic regulator of protein kinase C, and the calcium ionophore, ionomycin. Northern blot analysis of mRNA for early T-cell activation genes demonstrated the synergism between diC8 and ionomycin at the gene induction level. To amplify very low levels of IL-2 mRNA, sequential reverse transcription and polymerase chain reaction (RT-PCR) of T cell mRNA were used to demonstrate the capacity of the calcium signal (ionomycin) to promote low-level IL-2 transcription in normal human T-cells without additional signals. Cyclosporine (CsA) prevented diC8 and ionomycin-induced expression of IL-2, IFN-gamma, and H-ras genes. The completeness of its inhibitory effect was evident by the absence of IL-2 transcripts in CsA-treated cultures screened by the RT-PCR technique. CsA also prevented IL-2 and IFN-gamma gene expression in accessory cell-depleted T-cells stimulated by cross-linking the CD2 and CD3 antigens on the cell surface. Our observations demonstrate that a physiologic regulator of PKC, diC8, and cell surface crosslinking of the CD2 and CD3 antigen, promote gene expression in normal human quiescent T-cells independently of accessory cells, and that CsA prevents gene expression via a direct effect on T-cells.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1988

The sternocleidomastoid myoperiosteal flap for esophagopharyngeal reconstruction and fistula repair: clinical and experimental study.

Despite advances in head and neck surgery, reconstruction of the pharynx and cervical esophagus continues to be troublesome. Classic pedicled flaps are often too bulky and difficult to position for repair of pharyngeal and esophageal fistulas. An ideal flap would be local, well-vascularized, compact, and capable of being sutured into a tension-free, water-tight seal. In selected cases, the sternocleidomastoid myoperiosteal flap can meet these requirements in a single-stage procedure for repair of fistulas as well as selected cases of primary pharyngeal reconstruction. The use of this flap is described in five patients. Two patients underwent laryngectomy with partial pharyngectomy that left inadequate mucosa for primary closure. A sternocleidomastoid myoperiosteal flap was used to add width to the remaining mucosa. Both patients healed within 3 weeks and remained stricture free. Three other patients who underwent radiation followed by tumor resection and standard primary closure of the pharynx developed fistulas. Two fistulas were repaired successfully with the sternocleidomastoid myoperiosteal flap, and both patients were able to eat a general diet on the eighth postoperative day. Reconstruction was also performed in dogs to histologically evaluate the epithelialization capacity of the periosteum. There was total epithelialization of the flap at 4 weeks after reconstruction.

Aged↗

PubMed1986

Parietal occipital nape of neck flap. A myocutaneous flap for selected head and neck reconstruction.

Reconstruction in head and neck surgery has been greatly advanced with the use of the pectoralis major and trapezius myocutaneous flaps. Most surgical defects can be repaired with one of these flaps alone, or in conjunction with cutaneous flaps. Specific problems, however, occur that cannot be successfully reconstructed by these standard flaps. The traditional scalp flaps are cutaneous flaps. Use of these flaps is limited because of their shortened arc of rotation and accompanying forehead deformity. Three patients underwent reconstruction with a parietal occipital nape of neck myocutaneous flap. Its advantages include the following: large segments of hairless skin from the contralateral side of the neck can be used, an extensive arc of rotation and distance can be achieved with excellent vascularity in the overlying skin, and cosmetic results are superior. Angiographic studies were used to demonstrate the vascular pattern and supply to this flap. Cadaver dissections were performed to determine the pattern of distribution of the perforating vessels to the skin from underlying muscle.

Carcinoma, Squamous Cell↗

PubMed1986

Malignant tumors of the major salivary glands.

A total of 512 patients with major salivary gland tumors were treated at our institution between the years 1960 to 1975. The 147 cases of malignant salivary gland tumors were reviewed according to presenting characteristics and stage, histology, and outcome. Treatment for each type is summarized. The battery of diagnostic aids and prognostic indicators available to the physician are also reviewed. The newer and more controversial procedures of CT scanning, nuclear magnetic resonance scanning, and fine-needle aspiration are discussed in detail. In the past, salivary gland tumors have been classified by histology alone. Current trends employ the TNM staging system in planning treatment and predicting end results. We have found a far better survival rate in patients with various tumor types presenting with stage I or II disease, but point out that patients with high-grade tumors often present with advanced disease. All major salivary gland tumors should be approached according to the principles of cancer surgery. The minimum procedure is thus superficial or total parotidectomy with preservation of the facial nerve. In low-grade malignancies, the diagnostic procedure will have accomplished this definitive treatment. Salivary gland tumors are rare in the pediatric population. Such malignancies often defy radical treatment. Although cure rates in many categories of high-grade tumors are low, the only hope for survival is an initial aggressive surgical approach. Although radiation was used for recurrent disease only during the years of this study, it is currently being used as adjuvant therapy in almost all malignancies except low-grade mucoepidermoid. Recurrences are almost always fatal.

Adult↗

PubMed1984

Metastatic neck disease. Evaluation by computed tomography.

Computed tomographic (CT) scanning has been used in the preoperative examination of patients with head and neck cancer. Although early reports on the use of CT scanning for cervical lymphadenopathy were encouraging, the accuracy of CT in detecting nodal metastases has not been well established. Fifty consecutive patients underwent radical neck dissection and preoperative CT scanning. The clinical staging of the neck, CT diagnoses, and pathologic findings were correlated; CT accuracy was then compared with clinical accuracy. Our findings show the overall accuracy of CT diagnoses to be 90%. Comparison with clinical accuracy shows the CT scan to be superior to the clinical examination, particularly in detecting occult metastases.

Diagnostic Errors↗

PubMed1983

Parathyroid localization by computed tomographic scanning.

Increased accuracy of parathyroid hormone assays has yielded an earlier diagnosis of primary hyperparathyroidism, often in an asymptomatic stage. Non-invasive modalities used to localize parathyroid abnormalities have not been accurate for small adenomas. Although arteriography has been shown to be accurate in detection of adenomas, the invasive nature of the study, as well as possible complications, minimizes its use in preoperative localization of parathyroid abnormalities. The computed tomographic (CT) scan was used preoperatively in eight patients to assess its accuracy in localizing parathyroid abnormalities. The radiographic findings were correlated with surgical and pathologic findings. The conditions of seven patients were correctly diagnosed preoperatively by the CT scan, including that of one patient with diffuse hyperplasia. With the increased accuracy attained by this noninvasive examination, we believe that CT scanning should be a routine part of the preoperative examination of patients with primary hyperparathyroidism.

Adenoma↗

PubMed1982

Radiation therapy for subclinical carcinoma in cervical lymph nodes.

Radiotherapy alone was used to treat 187 patients with a head and neck cancer and clinically uninvolved lymph nodes. Delayed lymph node metastases developed in 35 (19%) patients, and concomitant tumor at the primary site was present in 90% of them. In two (1%) of the 187 patients, delayed metastases developed in the irradiated nodes with the primary tumor controlled; both of these patients received a radiation dose of less than 5,000 rad. Metastases in supraclavicular and posterior cervical regions occurred in 4% of the patients; and these sites were not included in the original radiation fields. The following conclusions were reached: (1) a radiation dose of 5,000 rad or more can eradicate 99% of the subclinical carcinomas in lymph nodes; (2) whole-neck irradiation is not indicated in patients with N0 stage tumor; and (3) surgical resection of primary tumors alone, without added neck dissection, may be adequate if postoperative radiation therapy is planned.

Carcinoma, Squamous Cell↗

PubMed1973

In memoriam.

Explore the source record for details and available documents.

History, 20th Century↗

PubMedDate not supplied

Laryngeal injuries secondary to nasogastric tubes.

Laryngeal complications secondary to nasogastric intubation have been reported rarely in recent literature. Recent experience with three patients who developed laryngeal injuries related to nasogastric tubes prompted retrospective, experimental, and prospective studies to determine the mechanism of laryngeal injury. A review of the literature, as well as the clinical findings in our three patients, point to midline tube placement and the subsequent development of cricoid chondritis as the underlying etiology. An experimental study using anesthetized dogs was designed to compare histologically the effect on the larynx with nasogastric tubes placed in the midline, as opposed to nasogastric tubes in the lateral position. Results of the histologic study confirmed that midline tubes generate severe inflammation in the postcricoid region. One hundred patients were then evaluated roentgenographically to determine the incidence of midline tube placement in a random sample. Six percent of the patients had nasogastric tubes in the midline. Patients who have nasogastric tubes in place for more than three days or have a severe amount of discomfort should have an x-ray film to determine position of the tube. Midline tubes should be removed or replaced.

Aged↗

PubMedDate not supplied

Sternomastoid myoperiosteal flap for reconstruction of the subglottic larynx.

Reconstruction of the subglottis is usually required after resection of cricoid cartilage or tracheal tissue in cases of trauma, subglottic stenosis, or invasive thyroid carcinoma. There are multiple techniques available for reconstruction of the subglottic larynx, but most of them have a high rate of complications or graft failure. We have found the sternocleidomastoid myoperiosteal flap to be an ideal means of reconstruction. In an experimental study, we performed subglottic reconstruction using the sternomastoid myoperiosteal flap on 15 mongrel dogs to determine the presence of bone formation versus calcified fibrous scar. Radiologic studies suggested apparent metaplastic bone formation at the graft site, and histologic studies confirmed this. Functionally, 12 dogs had stable airways without stridor or subglottic narrowing. Three dogs died of complications. With successful reconstruction of large defects in the canine subglottis, attempts to repair large subglottic and tracheal defects in the human are feasible.

Animals↗