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Biomedical subjects

J Clark

Publications and source records attributed to J Clark.

At least 199 records · Page 11Linked to original sources
PubMed1996

Ascosteroside, a new antifungal agent from Ascotricha amphitricha. I. Taxonomy, fermentation and biological activities.

Ascosteroside, a novel antifungal compound, was isolated from the culture broth of Ascotricha amphitricha. This compound is an alpha-linked glycoside of a lanostane type triterpenoid. It is active against yeasts such as Candida albicans and Saccharomyces cerevisiae and against filamentous fungi but shows no activity against bacteria. It is not toxic to mammalian cells at concentrations up to 150 microM. In a mouse model, the compound afforded protection comparable to that of ketoconazole.

Animals↗
PubMed1996

Interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction as a diagnostic aid for synovial sarcoma.

Identification of the t(X;18)(p11.2;q11.2) that is associated with a high proportion of synovial sarcoma can be a useful diagnostic aid. The translocation results in fusion of the SYT gene on chromosome 18 to either the SSX1 or the SSX2 gene, two homologous genes within Xp11.2. Two-color interphase fluorescence in situ hybridization and reverse transcription polymerase chain reaction were assessed as approaches to identify the rearrangement in well characterized cases. The presence of the translocation, and the specific chromosome X gene disrupted, were inferred from the configuration of signals from chromosome-specific centromere probes, paints, and markers flanking each gene in preparations of interphase nuclei. Rearrangement was found in two cell lines and eight of nine tumor samples, including analysis of five touch imprints. This was consistent with cytogenetic data in four cases and reverse transcription polymerase chain reaction analysis using primers known to amplify both SYT-SSX1 and SYT-SSX2 transcripts. The transcripts were distinguished by restriction with LspI and SmaI. Contrary to previous suggestions, there was no obvious correlation between histological subtype and involvement of the SSX1 or SSX2 gene. These approaches could also be applied to the identification of tumor-free margins and metastatic disease.

Adolescent↗
PubMed1996

Clearance kinetics, biodistribution, and organ saturability of phosphorothioate oligodeoxynucleotides in mice.

We examined the dynamics of removal from circulation, tissue distribution, and persistence of phosphorothioate oligodeoxynucleotides (S-ODN) anti-tumor-necrosis-factor and a control of random sequence (randomer) in mice. After intravenous injection, the majority (96%) of S-ODN cleared rapidly from the circulation in the first two phases. In the first phase, 37.8 +/- 2.3% of the radioactivity had a mean half-life (t1/2) of 2.0 +/- 0.4 minutes. In the second phase, 58.1 +/- 1.5% of the radioactivity cleared with t1/2 of 12.6 +/- 0.2 minutes. The catabolic phase, constituting a minor proportion (4.1 +/- 0.8% of the total radioactivity), had a mean t1/2 of 2.7 +/- 0.5 hours. At a low dose (1 microgram) tissue distribution of both S-ODN anti-tumor-necrosis-factor and randomer were similar. The liver and kidneys were the major organs involved in uptake and removal of S-ODN. Autoradiographic studies showed the liver Kupffer cells to be the major site of uptake and renal urinary space for elimination. The clearance rate from the circulation was increased with the dose of S-ODN. In contrast, the fraction of radioactivity localized in the kidneys, liver, and spleen was decreased with increase in dosage. Furthermore, at a high dose (200 micrograms), the tissue distribution of the S-ODN anti-tumor-necrosis-factor differed significantly from the randomer. These findings have general significance in showing that the liver and kidneys are the major organs for removal of S-ODN and these organs are saturable at high doses. In addition, the results have specific importance in defining different parameters, dose and base composition, that affect utilization of antisense oligonucleotides for controlling gene expression in vivo.

Animals↗
PubMed1996

The transition from underground to legal syringe exchange: the New York City experience.

The most common method of syringe exchange program (SEP) development in the United States has been for SEPs to be started by activists without funding and then to become a government-funded community-based organization. This developmental process, which has not been studied to date, involves major organizational change. We report our findings on three New York City syringe exchanges experiencing this type of transition. Our data illustrate that following legalization, increased legitimacy and funding allowed all three SEPs to expand the size and scope of their programs (e.g., adding hours, sites, referral services, and the ability to support user groups), resulting in a rapid growth in participation (over 15,000 in 18 months). Regulation accompanying legalization posed significant challenges to SEPs, including added record-keeping and reporting tasks, increased demand for referrals, and accommodating evaluation, which affected already overburdened staffs. The transition process poses significant challenges to these developing organizations as well as opportunities for improved services.

Attitude of Health Personnel↗
PubMed1995

Long-range organization of reiterated sequences, including the SSX1 cDNA at the OATL1 cluster in Xp11.23.

Analysis of four YACs at the OATL1 locus was undertaken to determine the organization of locally repeated sequences within the OATL1 cluster. A restriction map of ICRFy900C0874, a 600-kb YAC, was constructed using a range of rare-cutting enzymes. Several markers were isolated from the OATL1 cluster, and the YAC map was used for their localization. Markers are shown to be reiterated within the OATL1 cluster, and fine-scale mapping has identified the accurate map position and organization of these repeated sequences within a 275-kb interval. The SSX1 gene involved in synovial sarcoma tumorigenesis and localized at the OATL1 cluster is also shown to be present in a minimum of five copies, all of which map to the aforementioned region. Several markers generated in this study have homologous counterparts at OATL2; they have been utilized to delimit the duplicated region at the OATL clusters. Although instability of one of the OATL1 YACs, ICRFy900F0501, has precluded a precise sizing of this interval, it has been possible to place an upper limit of 520 kb on this region of duplication.

Base Sequence↗
PubMed1995

Fusion of SYT to two genes, SSX1 and SSX2, encoding proteins with homology to the Kruppel-associated box in human synovial sarcoma.

We demonstrate that the cytogenetically defined translocation t(X;18)(p11.2;q11.2) found in human synovial sarcoma results in the fusion of the chromosome 18 SYT gene to either of two distinct genes, SSX1 or SSX2, at Xp11.2. The SSX1 and SSX2 genes encode closely related proteins (81% identity) of 188 amino acids that are rich in charged amino acids. The N-terminal portion of each SSX protein exhibits homology to the Kruppel-associated box (KRAB), a transcriptional repressor domain previously found only in Kruppel-type zinc finger proteins. PCR analysis demonstrates the presence of SYT-SSX1 or SYT-SSX2 fusion transcripts in 29 of 32 of the synovial sarcomas examined, indicating that the detection of these hybrid transcripts by PCR may represent a very useful diagnostic method. Sequence analysis has demonstrated heterogeneity in the fusion transcripts with the formation of two distinct SYT-SSX1 fusion junctions and two distinct SYT-SSX2 fusion junctions.

Adolescent↗
PubMed1995

Mutational analysis of Saccharomyces cerevisiae ARF1.

Wild type and eight point mutants of Saccharomyces cerevisiae ARF1 were expressed in yeast and bacteria to determine the roles of specific residues in in vivo and in vitro activities. Mutations at either Gly2 or Asp26 resulted in recessive loss of function. It was concluded that N-myristoylation is required for Arf action in cells but not for either nucleotide exchange or cofactor activities in vitro. Asp26 (homologous to Gly12 of p21ras) was essential for the binding of the activating nucleotide, guanosine 5'-3-O-(thio)triphosphate. This is in marked contrast to results obtained after mutagenesis of the homologous residue in p21ras or Gs alpha, and suggests a fundamental difference in the guanine nucleotide binding site of Arf with respect to these other GTP-binding proteins. Two dominant alleles were also identified, one activating dominant ([Q71L]Arf1) and the other ([N126I]) a negative dominant. A conditional allele, [W66R]Arf1, was characterized and shown to have approximately 300-fold lower specific activity in an in vitro Arf assay. Two high-copy suppressors of this conditional phenotype were cloned and sequenced. One of these suppressors, SFS4, was found to be identical to PBS2/HOG4, recently shown to encode a microtubule-associated protein kinase kinase in yeast.

ADP-Ribosylation Factor 1↗
PubMed1995

Operational issues in syringe exchanges: the New York City tagging alternative study.

It is estimated that 50% of the approximate 200,000 intravenous drug users (IDUs) in New York City (NYC) are infected with HIV. Syringe exchange, a common method of HIV prevention in many countries was legalized in NYC in 1992. As syringe exchange has gained public support and the number of functioning exchangers has grown in the country, more attention has been given to the study of operational characteristics of syringe exchanges. Syringe exchanges may be considered health service delivery organizations, and the specific methods of service delivery may greatly influence their effectiveness in reducing HIV risk behavior among injecting drug users. Improving operational characteristics of syringe exchanges requires both careful data collection, in order to reduce ambiguity in interpretation, and methods for cumulating knowledge, so that previous learning experiences need not be repeated with each new exchange. We report here on the practice of marking ("tagging") syringes distributed by exchanges in NYC during the period from 1990 through 1994. During this period the NYC exchanges operated illegally as underground exchanges, and then received legal status and expanded greatly. Developing regulations that reflect the reality of the program operations while allowing for monitoring and oversight is a complicated process, especially when implemented in states that maintain paraphernalia and prescription laws and where "unauthorized" possession of injection equipment remains a criminal activity under existing legal statutes. The particular situation in NYC which required the revision of existing regulations during a period of rapid program expansion and implementation of a large system of syringe exchange further illustrates the multiple pressures which accompany such a process. In order to implement meaningful regulations which maximize the public health benefits of syringe exchange programs on an individual and community level, recommendations are made.

HIV Infections↗
PubMed1995

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate in rats and mice.

Effects of gavage versus dosed feed administration on the toxicokinetics of benzyl acetate were studied in male F344 rats and B6C3F1 mice. Benzyl acetate was rapidly hydrolysed to benzyl alcohol and then oxidized to benzoic acid. After gavage administration of benzyl acetate in corn oil at 500 mg/kg (rats) and 1000 mg/kg (mice), high benzoic acid plasma concentrations were observed. In contrast, much lower benzoic acid plasma concentrations were found after dosed feed administration at about 615 mg/kg/day for rats and about 850 mg/kg/day for mice. Results show that although the daily doses of benzyl acetate are comparable, bolus gavage administration effectively saturated the benzoic acid elimination pathway whereas dosed feed administration did not. In contrast, hippuric acid plasma concentrations were similar after both gavage and dosed feed administration due to the depletion of the glycine supply pool. Study results could explain the different toxicity and carcinogenicity responses of benzyl acetate observed in 2-yr chronic gavage and dosed feed studies.

Administration, Oral↗
PubMed1995

Preoperative cisplatin and accelerated hyperfractionated radiation induces high tumor response and control rates in patients with advanced head and neck cancer.

BACKGROUND: Preoperative therapy with concurrent cisplatin infusion and accelerated hyperfractionated radiation has the potential to eradicate pools of resistant cells with high-growth fraction that accumulate during standard radiation therapy. Based on preliminary data showing a high complete response rate (necessary for organ preservation) in patients with advanced squamous cell cancer of the head and neck (stages III and IV), we conducted a multi-institutional study using accelerated hyperfractionated radiation to maximize local and regional tumor control without adding toxicity. PATIENTS AND METHODS: Preoperative radiation was given in 1.8 Gy fractions for 2 weeks followed by 1.2 Gy BID hyperfractionation to 46.7 Gy. Continuous infusion of cisplatin 20 mg/m2 was given on days 1 through 4 and 22 through 25. Patients were initially assessed with panendoscopy and were subsequently reassessed with biopsy of primary site (+/- nodes). Patients with negative primary site biopsy received additional hyperfractionated radiation to 76 Gy with simultaneous carboplatin 25 mg/m2 BID for 12 consecutive days. Patients with residual disease after 47 Gy had resection of primary site and node dissection. Of 69 patients treated, 56 were T3 and T4, and 46 were N1, N2, and N3; 17 patients (25%) were stage III and 50 (72%) were stage IV; in 2 patients (3%) the stage was unknown. RESULTS: Treatment was well tolerated with no grade IV toxicities, but there were 13 patients with grade III toxicities (mucositis, dysphagia, or hematological toxicity). Biopsy specimens were taken from 84% of the patients, and 81% of the primary sites showed pathologic complete response and 49% of the lymph nodes showed a pathologic complete response. Thirty-four patients underwent curative surgery. Eleven required resection of the primary and 23 required neck dissection only. At 2 years (median followup 12 months), 44 of 69 patients (64%) have no evidence of disease, 9 are dead of disease, 9 are dead of other causes, and 6 are alive with disease. Surgical toxicities were minimal and primarily limited to fibrosis in 12 patients, edema in 8 patients, tracheoesophageal fistula in 1 patient, and delayed wound healing in 1 patient. Late toxicities included xerostomia in 22 patients, dysphagia in 17, and speech impairment in 9. CONCLUSIONS: Preoperative concurrent radiotherapy and chemotherapy provides a high level of organ preservation and local and regional control because of the high complete response rate at the primary site. A planned neck dissection with minimal morbidity ensures local/regional control, as well as providing definitive staging information. A randomized evaluation is suggested for this program.

Adult↗
PubMed1995

Most comfortable loudness shift as a measure of speech attenuation by hearing protectors.

The feasibility of using most comfortable loudness (MCL) as a real-world measure of speech attenuation introduced by hearing protection devices (HPDs) was studied. The authors compared three insert HPDs and an earmuff under three test conditions: (a) monaural earphone listening, (b) binaural earphone listening, and (c) sound field listening. The earmuff was used only in the sound-field condition. In addition, three sets of fitting instructions were utilized. Twelve normal hearing subjects participated. Results indicate that MCL shift can be used as a simple measure of speech attenuation provided by HPDs. The observed MCL shifts were affected by the fitting instruction but not by the listening condition. Findings support the notion that MCL-based tests of speech attenuation by HPDs can be conducted reliably both in sound field and under earphones and may be a simple and valid tool for assessing changes in speech audibility due to the wearing of HPDs.

Adult↗
PubMed1995

The human SB1.8 gene (DXS423E) encodes a putative chromosome segregation protein conserved in lower eukaryotes and prokaryotes.

We report that the human gene SB1.8 (DXS423E) encodes a protein of 1233 amino acids that is highly homologous (30% identity) to the essential yeast protein SMC1 which is required for the segregation of chromosomes at mitosis. Both SB1.8 and SMC1 contain an N-terminal NTP binding site, a central coiled-coil region and a C-terminal helix-loop-helix domain, and have structural features in common with the force generating proteins myosin and kinesin. SB1.8 also exhibits regions of homology and overall structural similarity to the prokaryote (Mycoplasma hyorhinis) protein 115p. Thus SB1.8 and SMC1 are members of a highly conserved and ubiquitous family of proteins that appear to have a fundamental role in cell division. In addition we show that SB1.8 (DXS423E) maps to a cosmid contig that lies centromeric to the OATL2 locus at chromosome Xp11.2.

Amino Acid Sequence↗
PubMed1995

I-123 MIBG scintigraphy in adults. A report of clinical experience.

Thirty-one adult patients with clinical findings suggestive of pheochromocytoma were studied with I-123 MIBG. All patients had images obtained at 24 and 48 hours. Five patients had abnormal uptake proved to be because of I-123 MIBG avid tumors. The remaining 26 patients had no proven tumors and showed physiologic uptake in various organs. The 24-hour images were of high quality. In all cases, the 48-hour images contributed no significant additional information. Only in 1 patient did the 48-hour image add some certainty. Physiologic uptake was seen in the salivary glands, liver, G.I. tract, and urinary bladder in all patients (100%). Uptake was also observed in the lung and heart (90%), normal adrenal glands (32%), thyroid (29%), spleen (23%) uterus (13%), and neck muscles (6%). The authors' experience indicates that I-123 MIBG gives superior images compared to the previously used I-131 MIBG, that the optimum imaging time for adults is 18-24 hours, and that normal distribution patterns including uterine and neck muscle uptake should be familiar to physicians interpreting the studies.

3-Iodobenzylguanidine↗
PubMed1995

Antibiotic pharmacokinetics in the inflamed prostate.

We hypothesized that altered pharmacokinetics in the inflamed prostate gland might account for the treatment failure of clinically diagnosed chronic bacterial prostatitis. We employed a rat model of chronic bacterial prostatitis to investigate any pharmacokinetic differences that may exist between uninflamed and inflamed prostate glands. Four groups of animals were studied (treated and untreated control and prostatitis groups). Seven days of norfloxacin therapy cured 60% of the animals with well-established bacterial prostatitis compared with a spontaneous cure rate of 10% in the nontreated prostatitis animals. Norfloxacin levels did not change significantly between the infected and noninfected prostate glands. We conclude that failure of antibiotic therapy in chronic bacterial prostatitis is not due to significantly altered norfloxacin pharmacokinetics in the chronically inflamed prostate gland but rather to the difficulty of eradicating protected bacterial microcolonies within an infection-induced altered microenvironment deep within the prostate gland.

Animals↗