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Biomedical subjects

J Green

Publications and source records attributed to J Green.

At least 343 records · Page 19Linked to original sources
PubMed1994

hMSH2 mutations in hereditary nonpolyposis colorectal cancer kindreds.

It has recently been shown that hereditary nonpolyposis colorectal cancer (HNPCC) is caused by hereditable defects in DNA mismatch repair genes. However, the fraction of HNPCC due to defects in any one repair gene and the nature of these mutations are not known. We analyzed 29 HNPCC kindreds for mutations in the prototype DNA mismatch repair gene hMSH2 by a combination of linkage analysis, polymerase chain reaction-based screening, and sequencing of the coding region. The complete intron/exon structure of the gene was ascertained to facilitate this analysis. The results suggest that at least 40% of classic HNPCC kindreds are associated with germline mutations in hMSH2 and that most of these mutations produce drastic alterations in the predicted protein product.

Amino Acid Sequence↗
PubMed1994

Synthetic, structural and biological studies of the ubiquitin system: the total chemical synthesis of ubiquitin.

The small protein ubiquitin (76 amino acids) has been synthesized under optimized conditions by Merrifield solid-phase methodology using the N alpha-Fmoc protecting group. The crude polypeptide mixture was purified to homogeneity by gel filtration, dialysis and a combination of cation- and anion-exchange chromatography to yield ubiquitin. Amino acid analysis, enzymic digestion and sequencing by automated Edman degradation were used to authenticate the primary structure. Isoelectric focusing and m.s. were used to demonstrate that the final product was greater than 98% pure with a final yield of 93 mg (4.3%) from a single synthesis on a 0.25 nmol scale.

Amino Acid Sequence↗
PubMed1994

Screening for cognitive impairment in older individuals. Validation study of a computer-based test.

OBJECTIVE: This study examined the validity of a computer-based cognitive test that was recently designed to screen the elderly for cognitive impairment. DESIGN: Criterion-related validity was examined by comparing test scores of impaired patients and normal control subjects. Construct-related validity was computed through correlations between computer-based subtests and related conventional neuropsychological subtests. SETTING: University center for memory disorders. PARTICIPANTS: Fifty-two patients with mild cognitive impairment by strict clinical criteria and 50 unimpaired, age- and education-matched control subjects. Control subjects were rigorously screened by neurological, neuropsychological, imaging, and electrophysiological criteria to identify and exclude individuals with occult abnormalities. RESULTS: Using a cut-off total score of 126, this computer-based instrument had a sensitivity of 0.83 and a specificity of 0.96. Using a prevalence estimate of 10%, predictive values, positive and negative, were 0.70 and 0.96, respectively. Computer-based subtests correlated significantly with conventional neuropsychological tests measuring similar cognitive domains. Thirteen (17.8%) of 73 volunteers with normal medical histories were excluded from the control group, with unsuspected abnormalities on standard neuropsychological tests, electroencephalograms, or magnetic resonance imaging scans. CONCLUSIONS: Computer-based testing is a valid screening methodology for the detection of mild cognitive impairment in the elderly, although this particular test has important limitations. Broader applications of computer-based testing will require extensive population-based validation. Future studies should recognize that normal control subjects without a history of disease who are typically used in validation studies may have a high incidence of unsuspected abnormalities on neurodiagnostic studies.

Aged↗
PubMed1994

Genomic diversity of small round structured viruses in the United Kingdom.

Fifty-two faecal specimens collected in the United Kingdom between 1986 and 1992, which contained small round structured virus (SRSV) particles, were tested by reverse transcriptase polymerase chain reaction assays using two primer pairs derived from sequences of Snow Mountain Agent and Norwalk virus. There was poor correlation between results obtained with each primer pair. Twenty specimens (38%) gave positive bands with SM51/31 primers and 18 (34%) were positive with SM52/32 primers, with a total of 30 specimens (57.7%) giving amplification products of the expected size with one or both primer pairs. Genomic variation was investigated by sequencing a 266 bp region of the RNA polymerase gene from nine strains which had been antigenically typed by solid phase immune electron microscopy (SPIEM). RNA sequence identities ranged from 53 to 99%. Three genomic groups were suggested by phylogenic analysis, the first of which contained Norwalk virus, Southampton virus, and strains typed by SPIEM as SRSV UK2. The second contained Snow Mountain agent and strains typed as either SRSV UK3 or UK4. The third contained strains typed as SRSV UK1 and strains untypeable by SPIEM. Some correlation was demonstrated when antigen typing by SPIEM and phylogenic grouping based on sequence data were compared.

Adult↗
PubMed1994

1,25(OH)2-16ene-vitamin D3 is a potent antileukemic agent with low potential to cause hypercalcemia.

Compounds that induce cancer cells to differentiate are clinically effective for several types of malignancies. The 1,25-dihydroxyvitamin D3[1,25(OH)2D3(C)] induces leukemic cells, including HL-60, to differentiate and/or no longer proliferate, but it causes hypercalcemia. Development of vitamin D analogs that are more potent in their abilities to affect leukemic cells without causing greater hypercalcemia, may be useful therapeutically. A novel analog [1,25(OH)2-16ene-D3(HM)] has a double bond between C-16 and C-17; it appears to be an extremely effective antileukemic agent with the same or fewer effects on serum calciums. We define the potency of this compound and compare it with seven, previously reported, potent analogs of 1,25(OH)2D3. HM inhibited clonal growth of HL-60 cells by 50% at 1.5 x 10(-11) M. This was about equipotent to 1,25(OH)2-16ene-23yne-D3(V), about 100-fold more potent than many of the other analogs, and 1000-fold more potent than 1,25(OH)2D3. The rank order of leukemic inhibitory activity was: 1,25(OH)2-16ene-D3(HM) > or = 1,25(OH)2- 16ene-23yne-D3(V) > 1,25(OH)2-23ene-D3(EX) = 1,24(OH)2-22ene-24-cyclopropyl-D3(BT) = 22-oxa- 1,25(OH)2D3(EU) = 1,25(OH)2-24-homo-D3(ER) > 1,25(OH)2D3(C) > 1,25(OH)2-24- dihomo-D3(ES). The rank order of their effects on induction of differentiation of HL-60 cells, as measured by superoxide production and nonspecific esterase activity, was similar to their antiproliferative activities. In contrast, each analog slightly stimulated proliferation of normal human myeloid clonal growth. Serum calcium levels were the same or slightly less when either 1,25(OH)2-16ene-D3(HM) or 1,25(OH)2D3 (0.0625, 0.125, or 0.25 microgram) was given intraperitoneally to mice for 5 weeks. HM bound to 1,25(OH)2D3 receptors about 1.5-fold more avidly than 1,25(OH)2D3. In fact, this vitamin D3 appears to be the most avid binder to 1,25(OH)2D3 receptors that has been identified to date. In contrast, HM had a greater than 50-fold lower affinity for the D-binding proteins as compared with 1,25(OH)2D3, thus increasing the availability of the compound for target tissues. Further differentiation experiments showed that HM was more potent than 1,25(OH)2D3 in the presence of serum, but was equipotent in serum-free conditions. Taken together, our experiments suggest that 1,25(OH)2-16ene-D3(HM) may be more potent than 1,25(OH)2D3(C) because of its higher affinity to the 1,25(OH)2D3 receptors and its low affinity to the D-binding protein present in serum. HM is an ideal compound for clinical studies including patients with preleukemia and other neoplasia, as well as several skin disorders, such as psoriasis.

Antineoplastic Agents↗
PubMed1994

Cytogenetic and fluorescence in situ hybridization studies on sporadic and hereditary tumors associated with von Hippel-Lindau syndrome (VHL).

We performed cytogenetic and fluorescence in situ hybridization (FISH) studies on 29 sporadic or familial tumors associated with von Hippel-Lindau [correction of Landau] disease. Four of five renal cell carcinomas with detectable alterations showed clones with chromosome 3 alterations. These changes led to loss of genetic material visible with cytogenetic resolution: either an unbalanced translocation involving 3p or loss of a whole homolog 3, resulting in monosomy of 3p. We have previously mapped the VHL gene to chromosomal region 3p25-p26. We applied FISH using the single copy probes cA233 and cA479, sequences close to the VHL gene, in a search for submicroscopic deletions of 3p. Use of FISH with differentially labeled probes indicated cA479 to be distal to cA233, but both were located within bands 3p25-26. FISH with single copy probes for interphase cytogenetics detected four subclones with deletions in the VHL region in 8/22 tumors, including four tumors which appeared cytogenetically normal. FISH proved to be a powerful tool in tumor genetic studies, especially helpful in detecting tumor subclones in benign and slowly growing tumors.

Adrenal Gland Neoplasms↗
PubMed1994

Regulation of transcription at the ndh promoter of Escherichia coli by FNR and novel factors.

FNR is a transcriptional regulator that controls gene expression in response to oxygen limitation in Escherichia coli. The NADH dehydrogenase II gene (ndh) is repressed by FNR under anaerobic conditions. Repression is not simply due to occlusion of the promoter (-35 and -10) region by FNR because adjacent pairs of FNR monomers were found to bind at two sites centred at -50.5 and -94.5 in the ndh promoter region without preventing RNA polymerase binding. However, contact between RNA polymerase and the -132 to -62 region of the non-coding strand of ndh DNA, and RNA polymerase-mediated open complex formation, were prevented by bound FNR. The upstream FNR-binding site (-94.5) was needed for efficient FNR-dependent repression of ndh transcription in vitro, and also for repression of an ndh-lacZ fusion in vivo. Anaerobic ndh repression may thus involve the binding of two pairs of FNR monomers upstream of the -35 region, which prevents essential RNA polymerase-DNA contacts in the upstream region as well as inhibiting RNA polymerase function by direct FNR interaction. Expression of the ndh-lacZ fusion in an fnr deletion strain was enhanced by anaerobic growth in rich medium or minimal medium supplemented with amino acids. Furthermore, two proteins (M(r) 12,000 and 35,000) which interact with and may activate transcription from the ndh promoter under these conditions were detected by gel retardation analysis. These putative amino acid-responsive activators may thus offset FNR-mediated repression and maintain a low level of anaerobic ndh expression for regulating the NAD+/NADH ratio during growth in rich media.

Amino Acids↗
PubMed1994

Seasonal variation in the necropsy incidence of massive pulmonary embolism.

AIMS: To investigate the seasonal incidence of massive pulmonary embolism at necropsy. METHODS: Massive pulmonary embolism was defined as a recent thromboembolus occluding the pulmonary trunk or one or both main pulmonary arteries and constituting the main cause of death. A total of 4289 necropsies carried out at East Birmingham Hospital from 1979 to 1988 was reviewed. The number of subjects with massive pulmonary embolism was noted and the accumulated percentage for each calendar month was calculated. RESULTS: Massive pulmonary embolism was found in 13.02% of necropsies carried out in April; in September and October the percentage rose to 14.29 and 14.19, respectively, after falling to 8.04 and 7.80 in June and July. In January and February the incidence fell again to about 9%. CONCLUSIONS: The incidence of massive pulmonary embolism at East Birmingham Hospital is highest in the spring and autumn. Investigation of the seasonal incidence in arctic and tropical areas would be of interest.

Autopsy↗
PubMed1994

Endothelin receptor in osteoblastic cells is coupled to multiple messenger signals.

We analyzed the functional characteristics of endothelin (ET) peptides in the osteoblastic UMR-106 cells by studying receptor binding as well as dose-response curves for ET-1 and ET-3 on two biological responses: 1) induction of Ca2+ transients and 2) activation of the Na(+)-H+ exchanger. ET specifically binds to a single class of receptor with a rank order of affinity ET-1 >> ET-3. ET-1 and ET-3 dose dependently stimulated a rise in intracellular Ca2+ ([Ca2+]i), with ET-1 being two orders of magnitude more potent than ET-3 [50% effective concentration (EC50) = 8 x 10(-10) and 9 x 10(-8) M for ET-1 and ET-3, respectively; P < 0.01]. The effect of ET-1 on [Ca2+]i was 90% inhibitable by the ETA antagonist BQ-123. The activity of Na(+)-H+ exchange was studied by using the pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein as well as by 22Na+ fluxes. ET-1 and ET-3 activated the exchange in a concentration-dependent manner and with similar potencies (EC50 approximately 10(-10) M). The action of ETs on Na(+)-H+ exchange was mimicked neither by phorbol esters nor by Ca2+ ionophores. It was, however, blocked by BQ-123 as well as by the protein tyrosine kinase inhibitor genistein. We conclude that in UMR-106 cells, a single ET receptor subtype is coupled to multiple effectors, a Ca2+ message system and a tyrosine-kinase system which, in turn, activates the Na(+)-H+ exchanger.

Animals↗
PubMed1994

Interleukin-6 attenuates agonist-mediated calcium mobilization in murine osteoblastic cells.

Interleukin-6 (IL-6) is a multifunctional cytokine which is made by osteoblasts and has diverse effects on bone metabolism. We studied the interaction of IL-6 with the Ca2+ and cAMP signaling systems in the osteoblastic cell line UMR-106 and in primary osteoblastic cultures derived from neonatal rat calvariae. IL-6 did not alter basal intracellular calcium concentration ([Ca2+]i) but inhibited Ca2+ transients induced by parathyroid hormone (PTH), prostaglandin E2 (PGE2), and endothelin-1 in both dose- (100-400 U/ml) and time- (4-48 h) dependent manners. The effect of the cytokine was abolished by the tyrosine kinase inhibitor, herbimycin A (50 ng/ml). The IL-6 effect on the Ca2+ message system was related to suppressed production of hormonally induced inositol 1,4,5-triphosphate and inhibition of Ca2+ release from intracellular stores. Hormonally induced calcium entry pathways (estimated by using Mn2+ as a surrogate for Ca2+) were not, however, altered by the cytokine. IL-6 did not modulate cAMP generation in osteoblasts. With respect to osteoblast function, IL-6, although having no effect on cell proliferation by itself, greatly enhanced the antiproliferative effect of PGE2 and PTH. Because the production of IL-6 in osteoblasts is stimulated by calciotropic hormones (e.g., PTH and PGE2), the suppressive effect of the cytokine on hormonally induced Ca2+ transients may serve as an autocrine/paracrine mechanism for modulating the effect of hormones on bone metabolism.

Animals↗
PubMed1994

The influence of the setting of 'cut-off' points for orthodontic treatment need upon the reliability of the Index of Orthodontic Treatment Need.

This investigation evaluated the effect of setting cut-off points for treatment allocation upon the reliability of the Index of Orthodontic Treatment Need (IOTN). Cut-off points were placed between the grades signifying 'need' and 'moderate need' and between 'need' and 'no need' for treatment. The reliability of each of these dichotomous decisions was evaluated with (i) the Kappa statistic and (ii) the false positive and false negative rates. We found that the reliability was decreased and the false positive rate was increased when the cut-off point was placed between the 'need' and 'moderate need' for treatment levels. The effect of this variation in reliability is discussed.

Esthetics, Dental↗
PubMed1994

The $147,000 misunderstanding: repercussions of overestimating the cost of AIDS.

The increasing incidence of AIDS in the 1980s prompted inquiry into the resources required to meet projected needs. In the first economic study to appear on the illness, the Centers for Disease Control (CDC) estimated that the costs of inpatient care were $147,000 per AIDS patient, heightening concern that the health care system would be overwhelmed by the epidemic. However, every study published subsequently has produced much lower cost estimates. As a result, many have concluded that treatment costs declined due to improved delivery of AIDS care. We offer an alternative interpretation, based on evidence demonstrating that the CDC's methods and assumptions yielded a figure about three times too high. The CDC's erroneous estimate had significant policy repercussions. Using the $147,000 figure, the health insurance industry lobbied successfully for the right to screen applicants for HIV. Next, when a study of San Francisco AIDS patients found local hospital costs per case to be $27,571, many concluded that billions of dollars could be saved if the "San Francisco model" of care (emphasizing home and community-based services and case management) were universalized. Since then, most programs for AIDS services have provided funds for community care. While such programs improve access to vital services, they are unlikely to guarantee "better care for less money." A more informed understanding of the cost of AIDS should lead to programs that also strengthen inpatient care.

AIDS Serodiagnosis↗
PubMed1994

Circulatory disturbance and renal dysfunction in liver disease and in obstructive jaundice.

The appearance of hepatorenal syndrome in a patient with acute or chronic liver disease is associated with a dismal outcome. Thus, management of HRS remains a formidable challenge to the aggressiveness and perseverance of the physician. The best treatment for HRS remains prevention based on avoidance of circulating volume contraction or the use of nephrotoxic drugs. Treatment for established HRS remains a frustrating experience with recovery being rare. A successful liver transplantation is currently the only definitive treatment that can reverse HRS. As this procedure is being performed with increasing frequency and encouraging results, a new window of hope has been opened for these patients.

Adult↗
PubMed1994

Cytosolic pH regulation in osteoblasts.

The process of bone formation depends on an optimal alkaline pH in the extracellular milieu surrounding the osteoblast. To the extent that ionic composition of an extracellular environment is determined by events taking place inside the cell, it is conceivable that the pH in the fluid outside the osteoblast is affected by cytosolic pH (pHi) regulation by these cells. Under HEPES-buffered conditions, the main pH regulatory mechanism is the ubiquitous acid-extruding mechanism, Na+/H+ exchange. However, under the more physiologic HCO3- environment, one can identify three additional acid-bone transporters: Na(+)-independent Cl-/HCO3- exchanger, Na+(HCO3-)3 cotransporter, and HCO(3-)-conductive pathway. In addition to their role in regulation of pHi in the osteoblast, these transporters also play a role in volume regulation of these cells both under hypertonic conditions (regulatory volume increase) and during osmotic swelling (regulatory volume decrease). Second messengers produced by calciotropic hormones (e.g. cytosolic Ca2+, cAMP) regulate the activity of Na+/H+ exchanger and Cl-/HCO3- exchanger.

Animals↗
PubMed1994

The physicochemical structure of bone: cellular and noncellular elements.

Bone responds to systemic acid base perturbations through an ionic exchange with the systemic extracellular fluid which, in its extreme form, culminates in dissolution of the skeletal tissue as observed in chronic acidotic states. As a major reservoir for the body stores of calcium, phosphorus, carbonate, citrate, magnesium and sodium the bone may use these ions in order to buffer massive loads of protons during acute metabolic acidosis. The total skeletal mass consists of two components: (1) an organic unmineralized matrix which includes mainly type 1 collagen and which comprises about one third of total bone weight and (2) the inorganic mineral phase of bone which constitutes about two thirds of the skeleton and is mainly composed of hydroxyapatite crystals (the main form of bone mineral). States of chronic metabolic acidosis lead to a gradual and progressive resorption of both the organic and inorganic components of bone. This process is carried out both by a direct physicochemical effect of the excess protons and through activation of the two main bone cell types, the osteoblasts and osteoclasts. In order to fully comprehend the nature of bone-systemic circulation interface, it is essential to understand the microanatomy and the physicochemical structure of bone.

Animals↗