Search PubMed⌕ Search

Biomedical subjects

D Goldfarb

Publications and source records attributed to D Goldfarb.

At least 19 recordsLinked to original sources
PubMed2000

Two-dimensional ENDOR-ESEEM correlation spectroscopy

A two-dimensional (2D) experiment that correlates electron-nuclear double resonance (ENDOR) and electron spin-echo envelope modulation (ESEEM) frequencies, useful for unraveling and assigning ENDOR and ESEEM spectra from different paramagnetic centers with overlapping EPR spectra, is presented. The pulse sequence employed is similar to the Davies ENDOR experiment with the exception that the two-pulse echo detection is replaced by a stimulated echo detection in order to enhance the resolution in the ESEEM dimension. The two-dimensional data set is acquired by measuring the ENDOR spectrum as a function of the time interval T between the last two microwave pulses of the stimulated echo detection scheme. This produces a series of ENDOR spectra with amplitudes that are modulated with T. Fourier transformation (FT) with respect to T then generates a 2D spectrum with cross peaks connecting spectral lines of the ESEEM and ENDOR spectra that belong to the same paramagnetic center. Projections along the vertical and horizontal axes give the three-pulse FT-ESEEM and ENDOR spectra, respectively. The feasibility of the experiment was tested by simulating 2D ENDOR-ESEEM correlation spectra of a system consisting of an electron spin (S = (1/2)) coupled to two nuclei (I(1) = I(2) = (1/2)), taking into account experimental conditions such as pulse durations and off-resonance irradiation frequencies. The experiment is demonstrated on a single crystal of Cu(2+) doped l-histidine (Cu-His), containing two symmetrically related Cu(2+) sites that at an arbitrary orientation exhibit overlapping ESEEM and ENDOR spectra. While the ESEEM spectrum is relatively simple and arises primarily from one weakly coupled (14)N, the ENDOR spectrum is very crowded due to contributions from two nonequivalent nitrogens, two chlorides, and a relatively large number of protons. The simple ESEEM projection of the 2D ENDOR-ESEEM correlation spectrum is then used to disentangle the ENDOR spectrum and resolve two sets of lines corresponding to the different sites. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Development of specific monoclonal antibodies and a sensitive discriminatory immunoassay for the circulating tumor markers SCCA1 and SCCA2.

The squamous cell carcinoma antigen (SCCA) serves as a serologic marker for advanced squamous cell carcinomas (SCC) of the uterine cervix, lung, esophagus, head and neck and vulva. Elevations in serum levels of SCCA following treatment for SCC correlate with tumor relapse or metastasis. Recent molecular studies show that SCCA is transcribed by two nearly identical genes (SCCA1 and SCCA2) that encode for members of the high molecular weight serine proteinase inhibitor (serpin) family. Despite a high degree of similarity in their amino acid sequences, SCCA1 and SCCA2 have distinct biochemical properties: SCCA1 is an inhibitor of papain like cysteine proteinases, such as cathepsins (cat) L, S and K, whereas SCCA2 inhibits chymotrypsin-like serine proteinases, catG and mast cell chymase. In this paper, we report the generation and characterization of anti-SCCA1 and anti-SCCA2 specific monoclonal antibodies (MAbs). Using these MAbs, we developed an enzyme-linked immunoassay (ELISA) that discriminated between SCCA1 and SCCA2 without any cross-reaction. This assay measured both the native and complexed forms of SCCA1 and SCCA2. The sensitivity of detection of SCCA1 and SCCA2 assays were 0.17 ngml(-1) and 0.19 ngml(-1), respectively. Mean inter- and intra-assay coefficients of variation were 12.1% and 9.9% for SCCA1 assay and 12% and 8.8% for SCCA2 assay, respectively. Recovery and parallellism studies indicated that SCCA1 and SCCA2 were detected in the plasma and amniotic fluids without any major interference by the biologic fluid components. This assay provides a simple and accurate procedure for the quantitation of total SCCA1 and SCCA2.

Animals↗
PubMed1999

A W-band pulsed ENDOR spectrometer: setup and application to transition metal centers.

The design and performance of a 95 GHz pulsed W-band EPR/ENDOR spectrometer is described with emphasis on the ENDOR part. Its unique feature is the easy and fast sample exchange at 4.2 K for frozen solution and single crystal samples. In addition, the microwave bridge power output is relatively high (maximum 267 mW), which allows the application of short microwave pulses. This increases the sensitivity in echo experiments because of the broader excitation bandwidth and the possibility of employing short pulse intervals, as long as the dead time does not increase significantly with the power. The spectrometer features two microwave and radiofrequency (0.1-220 MHz, 3 kW pulse power) channels and a 6 T superconducting magnet in a solenoid configuration. The magnet is equipped with cryogenic sweep coils providing a sweep range of +/-0. 4 and +/-0.2 T for a center field of 0-4 and 4-6 T, respectively. The spectrometer performance is demonstrated on Cu(II) centers in single crystals, a zeolite polycrystalline sample, and a protein frozen solution.

Copper↗
PubMed1999

Azide binding to the trinuclear copper center in laccase and ascorbate oxidase.

Azide binding to the blue copper oxidases laccase and ascorbate oxidase (AO) was investigated by electron paramagnetic resonance (EPR) and pulsed electron-nuclear double resonance (ENDOR) spectroscopies. As the laccase : azide molar ratio decreases from 1:1 to 1:7, the intensity of the type 2 (T2) Cu(II) EPR signal decreases and a signal at g approximately 1.9 appears. Temperature and microwave power dependent EPR measurements showed that this signal has a relatively short relaxation time and is therefore observed only below 40 K. A g approximately 1.97 signal, with similar saturation characteristics was found in the AO : azide (1:7) sample. The g < 2 signals in both proteins are assigned to an S = 1 dipolar coupled Cu(II) pair whereby the azide binding disrupts the anti-ferromagnetic coupling of the type 3 (T3) Cu(II) pair. Analysis of the position of the g < 2 signals suggests that the distance between the dipolar coupled Cu(II) pair is shorter in laccase than in AO. The proximity of T2 Cu(II) to the S = 1 Cu(II) pair enhances its relaxation rate, reducing its signal intensity relative to that of native protein. The disruption of the T3 anti-ferromagnetic coupling occurs only in part of the protein molecules, and in the remaining part a different azide binding mode is observed. The 130 K EPR spectra of AO and laccase with azide (1:7) exhibit, in addition to an unperturbed T2 Cu(II) signal, new features in the g parallel region that are attributed to a perturbed T2 in protein molecules where the anti-ferromagnetic coupling of T3 has not been disrupted. While these features are also apparent in the AO : azide sample at 10 K, they are absent in the EPR spectra of the laccase : azide sample measured in the range of 6-90 K. Moreover, pulsed ENDOR measurements carried out at 4.2 K on the latter exhibited only a reduction in the intensity of the 20 MHz peak of the 14N histidine coordinated to the T2 Cu(II) but did not resolve any significant changes that could indicate azide binding to this ion. The lack of T2 Cu(II) signal perturbation below 90 K in laccase may be due to temperature dependence of the coupling within the trinuclear : azide complex.

Ascorbate Oxidase↗
PubMed1998

Supersaturation and stone composition in a network of dispersed treatment sites.

PURPOSE: We determined the validity of urine supersaturation assessed from 2, 24-hour urine collections from outpatients eating uncontrolled diets and receiving care at a network of treatment sites that uses a central laboratory. We compared supersaturation to stone composition to determine whether supersaturation values correlate with composition. MATERIALS AND METHODS: Two 24-hour urine samples collected from 183 patients at 6 treatment sites were shipped to a single central laboratory. Complexations and crystallizations in vitro from aging during the transport step were interrupted by pH change in acid and alkaline directions. Relevant analytes were measured, and supersaturation was calculated for calcium oxalate, calcium phosphate as brushite and uric acid. Stone analysis was done at various laboratories. RESULTS: Urine supersaturation values correlated well with stone composition. Higher calcium phosphate and uric acid supersaturation was noted when stones contained higher amounts of calcium phosphate and any uric acid, respectively. In a validation study values of relevant urine materials were unchanged after 48 hours of aging. CONCLUSIONS: Despite the need for sample transport, resulting in the inevitable aging of samples, and variations in diet and details of sample collection, supersaturation values measured in only 2, 24-hour urine collections accurately reflected stone composition. This finding indicates that supersaturation values are reasonably stable in most patients during the months to years required for stones to form. In addition, samples collected in standard practice settings and sent to a central laboratory may accurately reflect these supersaturation values.

Calcium Oxalate↗
PubMed1996

Hyperfiltration nephropathy as a cause of late graft loss in renal transplantation.

Despite improved immunosuppression and early allograft survival, long-term survival of allografts remains unchanged. Late renal allograft loss has traditionally been considered to result from repeated or unresolved episodes of acute rejection that lead to chronic immune-mediated allograft rejection. However, late renal allograft loss is known to occur in the absence of prior episodes of acute rejection. It is therefore proposed that factors other than histocompatibility influence long-term allograft survival. Evidence for nonimmunologic factors contributing to late allograft loss is presented. The central hypothesis is that following renal allograft mass reduction (from any etiology), glomerular hyperperfusion and hyperfiltration develop and lead to progressive renal dysfunction, proteinuria, histopathologic allograft changes, and late allograft failure. Multiple nonimmunologic factors that could contribute to reduced renal mass and ultimately promote chronic allograft loss as a result of hyperfiltration nephropathy are presented along with possible therapeutic strategies for the prevention and treatment of glomerular hyperfiltration.

Glomerular Filtration Rate↗
PubMed1994

Two-state transition between molten globule and unfolded states of acetylcholinesterase as monitored by electron paramagnetic resonance spectroscopy.

Cys-231 of Torpedo californica acetylcholinesterase (EC 3.1.1.7) was selectively labeled with the mercury derivative of a stable nitroxyl radical. In 1.5 M guanidinium chloride, this conjugate exists in a molten globule state (MG), whereas in 5 M denaturant, it is in an unfolded state (U). The transition between the two states is reversible. In the MG, the label is highly immobilized, whereas in the U, it is almost freely rotating. The clearly distinct electron paramagnetic resonance (EPR) spectra of the two states permits the study of this transition. Upon elevating the guanidinium chloride concentration, a decrease in the EPR signal of the MG occurs concomitantly with an increase in the U signal, the total intensity of the EPR spectra remaining constant. This behavior is characteristic of a two-state transition. The thermodynamic characteristics of this transition (delta G0 and m), whether estimated directly from the EPR data or from both CD and fluorescence data analyzed by assuming a two-state scheme, are in good agreement.

Acetylcholinesterase↗
PubMed1994

Epidemiologic and clinical comparison of renal artery stenosis in black patients and white patients.

PURPOSE: This study was undertaken to compare the epidemiologic and clinical features of renal artery stenosis (RAS) in black patients and white patients. METHODS: Data on all patients identified with 50% or greater RAS from 1984 to 1990 were collected and analyzed. The study was conducted at the Cleveland Clinic Foundation, which is a referral center for patients with renal artery disease. Eight hundred nineteen patients with RAS were identified from an institutional registry that records information on patients with this disease. This group comprises 40 black patients (4.9%) and 779 white patients (95.1%). The presence of RAS was determined by abdominal aortography in all patients. Black patients and white patients with RAS were compared with respect to their age, sex, presence and severity of hypertension, renal function, type and extent of renal artery disease, extrarenal vascular disease, and risk factors such as history of smoking, diabetes, and hyperlipidemia. RESULTS: The mean age of black patients and white patients was 62 years; however, a greater proportion of black patients were women (p = 0.01). RAS was due to atherosclerosis in 95% and 92% of blacks and whites, respectively. Although the extent and severity of RAS were equivalent in black patients and white patients, more blacks were diagnosed with severe (p = 0.01) or refractory (p = 0.05) hypertension. Extrarenal vascular disease was present in 95% and 70% of blacks and whites, respectively (p < 0.01). The incidence of coronary artery disease (p < 0.01), cerebrovascular disease (p < 0.01), and peripheral vascular disease (p < 0.01) was greater among black patients. A history of smoking was more common among black patients (p < 0.01). Serum total cholesterol and low-density lipoprotein cholesterol levels were equivalent among black patients and white patients; however, black patients had higher high-density lipoprotein cholesterol (p = 0.03) and lower triglyceride (p < 0.01) levels. CONCLUSIONS: There are significant differences between black patients and white patients with RAS. The basis for these findings and their relationship to the cause and true prevalence of RAS in blacks requires further study.

Adult↗
PubMed1994

The impact of adjuvant nephrectomy on multimodality treatment of metastatic renal cell carcinoma.

Multimodality treatment of metastatic renal cell carcinoma with biological response modifiers and cytoreductive surgery has produced durable responses. The timing and impact of cytoreductive surgery on the success of immunotherapy require further study. We reviewed the treatment of 62 patients with metastatic renal cell carcinoma and primary tumors in place who qualified for multimodality treatment comprising adjuvant nephrectomy and biological response modifier protocols at our institution between 1987 and 1992. Of the patients 37 were scheduled to undergo initial adjuvant nephrectomy followed by biological response modifier therapy. A total of 25 patients underwent initial biological response modifier therapy with planned delayed adjuvant nephrectomy if a response to treatment was demonstrated. Of the 37 patients undergoing initial adjuvant nephrectomy, 8 (22%) were unable to enter induction of immunotherapy because of perioperative complications (1), medical contraindications (2), tumor progression (4) or death (1). Three patients in the initial adjuvant nephrectomy group (8%) had a partial response and the median survival in this group was 12 months (range 1 to 57). In the initial biological response modifier group 3 patients (12%) with an objective response (2 complete and 1 partial) to biological response modifier therapy underwent nephrectomy. The median survival for the initial biological response modifier group was 14 months (range 1 to 48). These results add to our understanding of the impact of adjuvant nephrectomy on patients with metastatic renal cell carcinoma considered for immunotherapy protocols.

Adult↗
PubMed1994

Magnetic resonance imaging of pelvic tumors in children.

Pelvic tumors in children may be large, complex and of unknown origin. Preoperative radiological information regarding tumor localization and extent becomes essential in these cases for proper staging and surgical planning. Magnetic resonance imaging (MRI) offers the ability to enhance the surgical preparation of children who present with a pelvic mass. Advantages of MRI over computerized tomography include improved soft tissue characterization, signal enhancement of neuroendocrine tumors and multiplanar imaging. These features better define the origin, size and extent of tumors. In addition, no ionizing radiation is required. Several examples of pelvic tumors are presented. The new anatomical information provided by MRI altered surgical planning previously based on computerized tomography findings alone.

Adolescent↗
PubMed1994

A new triple-balloon, four-channel vascular catheter for use in renal transplantation.

While current surgical techniques of renal transplantation afford excellent results, some steps of the operation are associated with potential morbidity. Application of vascular clamps on an atherosclerotic recipient artery can cause plaque fracture or atheroembolism. atheroembolism. Prolonged revascularization time may aggravate ischemic allograft damage. Based on the premise that arterial occlusion by an intraluminal balloon is less damaging to the vascular endothelium than an external vascular clamp, a new three-balloon, four-channel vascular catheter has been developed for use in renal transplantation. Catheters are inserted by the Seldinger technique, one catheter being positioned in each recipient external iliac artery and external iliac vein. Vascular control of the recipient vessels is obtained by inflation of the balloons. A pilot study in four dogs has confirmed the technical feasibility of using this catheter during renal transplantation. A description of the catheter, technique of surgical placement, advantages and potential uses is presented.

Animals↗
PubMed1994

Use of the thoracic aorta for renal arterial reconstruction.

PURPOSE: Thoracic aortorenal bypass is a new technique for surgical renal revascularization in patients with severe atherosclerosis of the abdominal aorta. In such cases, the thoracic aorta is often free of disease. METHODS: From 1989 to 1992, thoracic aortorenal bypass was performed in 23 patients with hypertension, abdominal aortic atherosclerosis, and celiac artery stenosis; in 21 patients, renal artery stenosis was present bilaterally or in a solitary kidney. RESULTS: There was one operative death. Among the remaining 22 patients, hypertension was cured or improved after operation in 19 (86%), and renal function was improved or stable in 21 (95%). CONCLUSIONS: Thoracic aortorenal bypass has several advantages and is a useful alternative to abdominal aortic replacement in selected older patients who require renal arterial reconstruction.

Aorta, Abdominal↗
PubMed1994

Laryngeal pacing as a treatment for vocal fold paralysis.

We summarize etiologies of vocal fold paralysis and current treatments. The recent literature involving electrical stimulation of the larynx is reviewed. Four canines were involved in a study to test a new laryngeal pacemaker system. This system was used to stimulate both the lateral cricoarytenoid and thyroarytenoid muscles. The data are taken from two of these canines. One of the goals was to stimulate the paralyzed side of the larynx based on the activity of the normal (nonparalyzed) side of the larynx. The best stimulation parameters for full addition of the paralyzed vocal cord were 3-7 V, pulse duration of 0.5 ms at a frequency of 84-100 Hz. Principles for electrode design and electrophysiologic parameters pertaining to laryngeal pacing are discussed. We believe that unilateral vocal fold paralysis may someday be treated by stimulating the paralyzed lateral cricoarytenoid and thyroarytenoid muscles to move in synchrony with the normal, unparalyzed, lateral cricoarytenoid and thyroarytenoid muscles.

Animals↗
PubMed1994

Reduced nuclear import of human immunodeficiency virus type 1 preintegration complexes in the presence of a prototypic nuclear targeting signal.

Nuclear import of the retroviral preintegration complex and integration of retroviral with host cell DNA are essential steps for completion of the virus life cycle. The preintegration complex of the lentivirus human immunodeficiency virus type 1 (HIV-1) displays karyophilic properties and, as a consequence, is rapidly directed to the host cell nucleus by an energy-dependent transport pathway. The karyophilic properties of nuclear proteins are governed by a nuclear localization sequence, the targeting function of which can be inhibited in the presence of excess targeting signals. Here we present evidence that the nuclear import of a large karyophile--the preintegration complex of HIV-1--is inhibited in the presence of a prototypic nuclear targeting signal of simian virus 40 T antigen. This points to a novel strategy which prevents establishment of the provirus by interrupting nuclear localization of HIV-1 DNA.

Amino Acid Sequence↗
PubMed1994

Lyme disease: a review for the otolaryngologist.

Lyme disease is an important consideration in the differential diagnosis of patients seen by the otolaryngologist. Facial paralysis is the most common sign. The otolaryngologist may also see patients with temporal mandibular joint pain, cervical lymphadenopathy, facial pain, headache, tinnitis, vertigo, decreased hearing, otalgia and sore throat. The incidence is increasing and known to be endemic to certain areas of the United States and abroad. This paper reviews the various ways Lyme disease appears to the otolaryngologist. Three cases along with a discussion including epidemiology, vector, animal host relationship, clinical manifestations and pathophysiology are included. The literature is reviewed and the treatment discussed.

Child↗
PubMed1993

A nuclear localization signal within HIV-1 matrix protein that governs infection of non-dividing cells.

Permissiveness of the host cell to productive infection by oncoretroviruses is cell-cycle dependent, and nuclear localization of viral nucleoprotein preintegration complexes will occur only after cells have passed through mitosis. In contrast, establishment of an integrated provirus after infection by the lentivirus HIV-1 is independent of host cell proliferation. The ability of HIV-1 to replicate in non-dividing cells is partly accounted for by the karyophilic properties of the viral preintegration complex which, after virus infection, is actively transported to the host cell nucleus. Here we report that the gag matrix protein of HIV-1 contains a nuclear localization sequence which, when conjugated to a heterologous protein, directs its nuclear import. In addition, HIV-1 mutants containing amino-acid substitutions in this nuclear localization signal integrate and replicate within dividing but not growth-arrested cells, and thus display a phenotype more representative of an oncoretrovirus.

Amino Acid Sequence↗