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Biomedical subjects

J Richards

Publications and source records attributed to J Richards.

At least 19 recordsLinked to original sources
PubMed1992

Proposed role of phosphatidic acid in the extracellular control of the transition from G2 phase to mitosis exerted by epidermal growth factor in A431 cells.

Epidermal growth factor (EGF) has been shown to cause an inhibition of A431 cells in G2 phase within approximately 10 min, i.e., shortly before mitosis (Kinzel et al., Cancer Res., 50: 7932-7936, 1990). This system has been used to study the proposed role phospholipid metabolites, particularly phosphatidic acid (PA), may play (Kaszkin et al., Cancer Res., 51: 4328-4335, 1991) in the extracellular control of cells at the physiological restriction site in G2 phase. A431 cells responded to EGF with a dose-dependent formation of phosphatidic acid (PA) which correlated with the dose-dependent G2 delay as well as with their time courses. The G2 delay induced by EGF as well as PA mobilization were effected in conditioned medium or in fresh medium containing bovine serum albimun instead of serum, i.e., under the conditions necessary for precursor studies to be carried out. The major pathway of PA formation was probably via phospholipase C-mediated breakdown of phosphatidylinositol and diacylglycerol kinase: (a) the dose response of PA formation correlated with that of total inositol phosphate accumulation; (b) little diacylglycerol was found and then only at a high EGF concentration; (c) prelabeling with [1-14C]arachidonic acid resulting in a large specific labeling of phosphatidylinositol led to an EGF-induced, dose-dependent formation of radioactive arachidonyl-PA (correlated with that of total PA and inositol phosphate), but in the presence of a primary alcohol not to the formation of radioactive phosphatidylalcohol; (d) prelabeling with [1-14C]oleic acid led to the EGF-induced formation of labeled PA, which in the presence of a primary alcohol was only slightly reduced to the advantage of very low levels of labeled phosphatidyl alcohol, thus demonstrating that an EGF-effected activation of phospholipase D did occur but contributed little to the general PA level. An alternative mobilization of PA was attempted with the phorbolester 12-O-tetradecanoylphorbol-13-acetate (TPA), which was shown to activate phospholipase D in A431 cells and to elicit PA from a phospholipid pool which was not significantly labeled with radioactive arachidonic acid. The TPA-induced degree of PA formation and of the G2 delay correlated. Both phenomena were considerably larger with fresh medium containing 0.5% bovine serum albumin instead of serum than in conditioned medium.(ABSTRACT TRUNCATED AT 400 WORDS)

Drug Synergism↗
PubMed1992

Expression cloning of a common receptor for parathyroid hormone and parathyroid hormone-related peptide from rat osteoblast-like cells: a single receptor stimulates intracellular accumulation of both cAMP and inositol trisphosphates and increases intracellular free calcium.

Parathyroid hormone (PTH), a major regulator of mineral ion metabolism, and PTH-related peptide (PTHrP), which causes hypercalcemia in some cancer patients, stimulate multiple signals (cAMP, inositol phosphates, and calcium) probably by activating common receptors in bone and kidney. Using expression cloning, we have isolated a cDNA clone encoding rat bone PTH/PTHrP receptor from rat osteosarcoma (ROS 17/2.8) cells. The rat bone PTH/PTHrP receptor is 78% identical to the opossum kidney receptor; this identity indicates striking conservation of this receptor across distant mammalian species. Additionally, the rat bone PTH/PTHrP receptor has significant homology to the secretin and calcitonin receptors but not to any other G protein-linked receptor. When expressed in COS cells, a single cDNA clone, expressing either rat bone or opossum kidney PTH/PTHrP receptor, mediates PTH and PTHrP stimulation of both adenylate cyclase and phospholipase C. These properties could explain the diversity of PTH action without the need to postulate other receptor subtypes.

Amino Acid Sequence↗
PubMed1992

Monoclonal anti-melanoma antibodies IKH-1 and IKH-2 which work on formalin-fixed, paraffin embedded tissues: characterization, clinical trials and comparative studies with HMB-45.

Mouse monoclonal antibodies (MoAbs), IKH-1 and IKH-2, were produced against cloned human melanoma cells, KHm-6, which were cultured with 12-O-tetradecanoylphorbol-13-acetate (TPA) and processed by formalin fixation and alcohol dehydration (FFAD). According to the biochemical analysis, antigenic substances which reacted with IKH-1 were 34.0-60.0 kDa glycoproteins, and those which reacted with IKH-2 were 33.5, 34.5 and 36.0 kDa glycoproteins. Immunoelectron microscopy revealed that reaction products of IKH-1 were seen in some membranous vesicles, premelanosomes and cell membrane of TPA-treated KHm-6 cells, while IKH-2 recognized only premelanosomal structures. Immunohistochemical tests revealed that IKH-1 and IKH-2 have a high sensitivity (94.0% and 85.0%, respectively) to formalin-fixed, paraffin-embedded (FFPE) tissue sections of malignant melanomas. IKH-1 had a high specificity and IKH-2 and 100% specificity to FFPE tissue sections of melanocytic lesions.

Animals↗
PubMed1992

Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal.

The effects of lithium chloride on ornithine decarboxylase (ODC) activity were compared in the adrenal and kidney of control (saline treated) and prolactin-treated rats. ODC activity was decreased in kidney of both groups of animals, the magnitude of the effect of lithium in the hormone-treated group varying with the time of administering the lithium relative to prolactin. The response in the adrenal was quite different. Following treatment with LiCl, there was a gradual increase in ODC activity from a low of 10-35 pmol CO2 x 30 min-1.mg protein-1 in control animals to values 20- to 30-fold greater at 5 h. In rats treated simultaneously with LiCl and prolactin, ODC activity was greater at 5 h than that observed in animals receiving either compound alone, indicating that their effects were additive. When LiCl was given 4 h after prolactin, i.e., 1 h before sacrifice, ODC activity decreased to a very low level at 5 h, as in other tissues. The increase in ODC activity in the adrenal following LiCl is of the same magnitude as the changes observed in tissues stimulated to undergo alterations in proliferation, differentiation, or metabolic or membrane activity by hormones and other external stimuli.

Adrenal Glands↗
PubMed1991

A G protein-linked receptor for parathyroid hormone and parathyroid hormone-related peptide.

The complementary DNA encoding a 585-amino acid parathyroid hormone-parathyroid hormone-related peptide (PTH-PTHrP) receptor with seven potential membrane-spanning domains was cloned by COS-7 expression using an opossum kidney cell complementary DNA (cDNA) library. The expressed receptor binds PTH and PTHrP with equal affinity, and both ligands equivalently stimulate adenylate cyclase. Striking homology with the calcitonin receptor and lack of homology with other G protein-linked receptors indicate that receptors for these calcium-regulating hormones are related and represent a new family.

Amino Acid Sequence↗
PubMed1991

A proposed common mechanism by which phorbol esters and epidermal growth factor delay the progression from G2 phase to mitosis of HeLa cells through phospholipid metabolites.

The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA; also called phorbol myristate acetate) and epidermal growth factor both rapidly inhibit the transition of HeLa cells from G2 phase to mitosis in a reversible fashion with characteristics of a receptor-mediated response. It was proposed that an intracellular mediator was responsible for this inhibition. In searching for a common mediator elicited by the action of both ligands, the time course of generation of phospholipid metabolites was compared with the cell cycle response of the G2 cohort monitored by time lapse analysis. The time course and the degree of mobilization of diacylglycerols (DG) effected by TPA and by epidermal growth factor and that of phosphatidic acid correlated to a great extent with the onset and the duration of the G2 inhibition caused by both agonists. Further evidence for the proposed role of DGs and/or phosphatidic acid was obtained by the observation that membrane-penetrating 1,2-DG inhibited HeLa cells in G2 phase directly. The concentration of DG required correlated with that elicited by TPA or epidermal growth factor metabolically. This cellular response to 1,2-DG was also seen in cells after down-regulation of protein kinase C using TPA. The data indicate that cellular DG and/or phosphatidic acid may contribute to a restriction of cells in G2 phase possibly by changing membrane properties.

Arachidonic Acids↗
PubMed1991

Volunteers for biomedical research. Recruitment and screening of normal controls.

We examined the process of accruing healthy control subjects for biomedical research on brain function. Of 1670 responders to newspaper advertising, 23.1% were uninterested when learning more about the studies, and 50.9% of those remaining were found by structured telephone screening to meet exclusionary criteria for having a history of psychiatric, neurologic, or medical disease that might affect brain function. Of 312 volunteers passing the telephone screening who came to an in-person evaluation by a physician and agreed to participate, 49.7% were found to meet exclusionary criteria, and only 157 were admitted to the study. This underscores the importance of attending to the issue of screening and assessment of "normal volunteers." Alternative strategies should be considered for enriching the pool.

Adult↗
PubMed1991

The influence of parenting stress and child behavior problems on parental estimates of expressive and receptive language development.

This study examined the relative contributions of parental reports of child-related and parent-related stress to their estimates of expressive and receptive language skills on the Minnesota Child Development Inventory in 152 children referred to a communicative disorders clinic. Correlational analysis showed moderately high agreement between parental estimates and objective measures of expressive and receptive language ability. Multiple-regression analyses revealed that independent measures of language acquisition accounted for the greatest amount of variance in parental estimates of expressive and receptive language skills. Stressful child behavior accounted for a small but statistically significant proportion of the variance in estimates of expressive and receptive language skills. Parental stress, in contrast, did not contribute significantly to language estimates. These findings suggest that parents are able to formulate estimates of language development which are relatively independent of personal or child-related stressors.

Child↗
PubMed1991

Effects of antioxidants and reduced oxygen tension on rat mammary epithelial cells in culture.

Free radical damage has the potential to significantly affect the behavior of cells in culture. In this study the effects of antioxidants (superoxide dismutase, catalase, and vitamin E) and lowered oxygen tension (1% oxygen) on primary culture of rat mammary epithelial cells were examined. Rat mammary epithelial cells were dissociated in collagenase with or without the addition of antioxidants and low oxygen tension, then cultured for 10 d in rat-tail collagen gel matrix and fed with Dulbecco's modified Eagle's F12 medium supplemented with various hormones and growth factors. Growth potential of the mammary cells was enhanced when antioxidants and low oxygen tension were used, alone or in combination, during the cell dissociation period. Using antioxidants and low oxygen tension during the culture period failed to improve growth potential regardless whether cells were dissociated in standard conditions or with antioxidants and low oxygen tension. The use of antioxidants and low oxygen tension during the cell dissociation period also reduced the degree of keratinization of the cells after 10 d of culture. Using antioxidants and low oxygen tension during the cell culture period did not further reduce keratinization if antioxidants and low oxygen tension were used during the dissociation period, but were effective in reducing keratinization if cells were dissociated in standard condition. In this system, antioxidants and low oxygen tension reduced lipid peroxidation during the cell dissociation period. An iron chelator, desferal, can also reduce lipid peroxidation and enhance growth when used during cell dissociation, suggesting the enhanced growth potential by the addition of antioxidants and low oxygen to be due to the reduction of lipid peroxidation.

Animals↗
PubMed1991

Relationship between cholinesterase inhibition and thermoregulation following exposure to diisopropyl fluorophosphate in the rat.

This study examined the relationship between inhibition of cholinesterase activity (CA) and thermoregulatory response in the rat following exposure to the organophosphate (OP), diisopropyl fluorophosphate (DFP). Male Long-Evans rats were injected with DFP dissolved in peanut oil in doses ranging from 0 to 1.5 mg/kg (s.c.). Colonic (Tcol) and tail skin temperature (Ttail) were recorded at 0, 1, 2 and 3 h post-injection. At 3 h post-injection the rat was sacrificed and a blood sample was taken by cardiac puncture and analyzed for CA. There was a biphasic dose effect of DFP on Tcol with slight but significant elevation in Tcol in the dose range of 0.01-0.5 mg/kg and a significant depression in Tcol at doses of 1.0 and 1.5 mg/kg. There was a dose-dependent fall in CA with DFP administration in the erythrocyte, plasma, and whole blood fractions. Hypothermia was associated with 80-87% inhibition in CA, whereas the elevation in Tcol was associated with 20-70% inhibition in CA. DFP also elicited significant elevations in Ttail. Overall, the data fail to demonstrate any clear relationship between inhibition of blood CA and thermoregulatory response following exposure to DFP. However, the elevation in Tcol following relatively low doses of DFP may be of relevance to the frequently reported symptom of fever in humans exposed to OP agents.

Animals↗
PubMed1991

Increased recombination adjacent to the Huntington disease-linked D4S10 marker.

Huntington disease (HD) is caused by a genetic defect distal to the anonymous DNA marker D4S10 in the terminal cytogenetic subband of the short arm of chromosome 4 (4p16.3). The effort to identify new markers linked to HD has concentrated on the use of somatic cell hybrid panels that split 4p16.3 into proximal and distal portions. Here we report two new polymorphic markers in the proximal portion of 4p16.3, distal to D4S10. Both loci, D4S126 and D4S127, are defined by cosmids isolated from a library enriched for sequences in the 4pter-4p15.1 region. Physical mapping by pulsed-field gel electrophoresis places D4S126 200 kb telomeric to D4S10, while D4S127 is located near the more distal marker D4S95. Typing of a reference pedigree for D4S126 and D4S127 and for the recently described VNTR marker D4S125 has firmly placed these loci on the existing linkage map of 4p16.3. This genetic analysis has revealed that the region immediately distal to D4S10 shows a dramatically higher rate of recombination than would be expected based on its physical size. D4S10-D4S126-D4S125 span 3.5 cM, but only 300-400 kb of DNA. Consequently, this small region accounts for most of the reported genetic distance between D4S10 and HD. By contrast, it was not possible to connect D4S127 to D4S125 by physical mapping, although they are only 0.3 cM apart. A more detailed analysis of recombination sites within the immediate vicinity of D4S10 could potentially reveal the molecular basis for this phenomenon; however, it is clear that the rate of recombination is not continuously increased with progress toward the telomere of 4p.

Animals↗
PubMed1991

Successful treatment of Bacillus cereus infection with ciprofloxacin.

Bacillus cereus is rarely a pulmonary pathogen but may cause pneumonia in immunocompromised patients. A patient with bronchiectasis and no recognisable immunodeficiency had this organism isolated during two infective exacerbations, once from respiratory secretions and once by blood culture. Ciprofloxacin treatment was effective on both occasions.

Adult↗
PubMed1991

Acute post-streptococcal glomerulonephritis.

Acute glomerulonephritis is characterized by the presence of hematuria, proteinuria and edema, and often hypertension and acute renal failure. Acute post-streptococcal glomerulonephritis is the prototypic disease of acute glomerulonephritis. It is seen after both streptococcal pharyngeal and skin infections with a latency period from infection to presentation of 7-14 days and 14-21 days respectively. Approximately 90 percent of post-streptococcal glomerulonephritis occurs in young children. The diagnosis is made by supporting evidence of recent streptococcal infection, a positive ASO-titer or Anti-DNAase B titer, with associated hypocomplementemia. The disease is self-limited and generally requires only supportive therapy with resolution occurring over a period of weeks to months. There are generally no permanent sequelae in children. Adults may have a higher incidence of hypertension and chronic renal failure as a result of post-streptococcal glomerulonephritis.

Acute Disease↗