Search PubMed⌕ Search

Biomedical subjects

L Wallace

Publications and source records attributed to L Wallace.

At least 73 records · Page 4Linked to original sources
PubMed1992

Immunodominant epitopes of HIV-1 p17 and p24.

Immunodominant antibody-binding sites were mapped using overlapping synthetic peptides of the structural proteins p17 and p24 of human immunodeficiency virus type 1 (HIV-1). Using sera from HIV-1-infected individuals at a variety of disease states, three major epitopes were identified within p17 and one within p24. Antibodies which recognized these epitopes were present in all risk groups throughout all stages of HIV infection, regardless of the presence of high levels of serum p24 antigen.

Amino Acid Sequence↗
PubMed1991

Bacterial flora of the uterus of cows after calving on two hygienically contrasting farms.

Intrauterine swabs were obtained from cows after calving on two commercial dairy herds with contrasting hygienic environments and incidence of leucorrhea, and cultured aerobically and anaerobically. Of 26 cows with a normal calving and puerperium, eight of 14 (57 per cent) were sterile on farm B where hygiene was poor, compared with five of 12 (42 per cent) on farm A where hygiene was better. Two cows on farm B retained their placentas and subsequently developed metritis/endometritis. Actinomyces pyogenes was the commonest bacterial isolate and Fusobacterium nucleatum, Proteus mirabilis and Bacteroides melaninogenicus were also frequently observed. Similar isolates were obtained from cows on farm B with parturient or puerperal disorders. The contrasting hygienic environments had no influence on either the quantitative or qualitative uterine bacterial flora. Thus, the difference in the incidence of endometritis must have been due to factors other than hygiene.

Actinomyces↗
PubMed1991

Treating Type A behaviours and mild hypertension in middle-aged men.

Unmedicated mildly hypertensive Type A men were randomly allocated to one of three conditions: stress management intervention training (N = 15), Type A management (N = 15), and delayed Type A management intervention. Significantly greater reductions in blood pressure at rest and during the Type A structured interview were found following the active interventions than during the minimal treatment control period of the delayed intervention. Type A management was more successful in changing a number of Type A behaviours, including anger, hostility and global Type A behaviour. Changes on measures of anger-in, -out, hostility, and SI ratings of Type A behaviour were associated with changes in systolic and diastolic blood pressure reactivity during interview.

Adult↗
PubMed1991

Osteoarthrotic changes after acute transarticular load. An animal model.

The canine patellofemoral joint was subjected to a standardized transarticular load of 2170 newtons for two milliseconds, and the gross and histological changes were examined at two, twelve, and twenty-four weeks after injury. Initially, the load creates fractures in the zone of calcified cartilage, with minimum damage to the articular cartilage surface. Surface fissures were visible in all patellae only after staining with India ink. Histologically, these surface clefts extended into the transitional or superficial radial zone, and they did not communicate with the subchondral bone except in two patellae. However, there were reproducible clefts in the region of the subchondral bone and the zone of calcified cartilage in all patellae. Six months after loading, there was a loss of safranin-O staining above the deep clefts, and there was new-bone formation in the subchondral region and fibrillation of the cartilaginous surface. Thus, the initial changes had progressed to osteoarthrotic-like conditions at six months. In this animal model, the joint is not invaded and the changes that result from loading are reproducible. The injury to the joint creates superficial disruption of the cartilage and subchondral changes that lead to arthritic-like degeneration of the cartilage within six months.

Animals↗
PubMed1991

Indoor/outdoor, and personal monitor and breath analysis relationships for selected volatile organic compounds measured at three homes during New Jersey TEAM-1987.

Indoor/outdoor relationships were identified for selected volatile organic compounds over the course of five consecutive days in three homes. Indoor sources of individual compounds were meant in one or more homes. Personal monitoring samples and breath analyses were obtained from volunteers in each home. A period of outdoor air stagnation occurred during one evening and morning of the study. Two results from the study that must be considered in future investigations of VOC exposure are 1) periods conducive to accumulating outdoor VOC can make substantial contributions to indoor values and 2) for homes without indoor sources of individual compounds the indoor values are driven by the outdoor values of a VOC. The primary results do not contradict previous TEAM studies which indicate that when indoor sources of a particular VOC are present the personal exposure and microenvironmental exposures are effected primarily by indoor contributions. Future comparisons of external exposure values with human breath analysis studies must be designed to more closely reflect the time interval associated with the half time of elimination for a particular VOC.

Air Pollutants↗
PubMed1991

The Los Angeles TEAM Study: personal exposures, indoor-outdoor air concentrations, and breath concentrations of 25 volatile organic compounds.

The U.S. Environmental Protection Agency and the California Air Resources Board studied the exposures of 51 residents of Los Angeles, California, to 25 volatile organic chemicals (VOCs) in air and drinking water in 1987. A major goal of the study was to measure personal, indoor, and outdoor air concentrations, and breath concentrations of VOCs in persons living in households that had previously been measured in 1984. Other goals were to confirm the marked day-night and seasonal differences observed in 1984; to determine room-to-room variability within homes; to determine source emission rates by measuring air exchange rates in each home; and to extend the coverage of chemicals by employing additional sampling and analysis methods. A total of 51 homes were visited in February of 1987, and 43 of these were revisited in July of 1987. The results confirmed previous TEAM Study findings of higher personal and indoor air concentrations than outdoor concentrations of all prevalent chemicals (except carbon tetrachloride); higher personal, indoor, and outdoor air concentrations in winter than in summer; and (in winter only) higher outdoor concentrations at night than in the daytime. New findings included the following: (1) room-to-room variability of 12-hour average concentrations was very small, indicating that a single monitor may be adequate for estimating indoor concentrations over this time span; (2) "whole-house" source emission rates were relatively constant during both seasons, with higher rates for odorous chemicals such as p-dichlorobenzene and limonene (often used in room air fresheners) than for other classes of chemicals; (3) breath concentrations measured during morning and evening were similar for most participants, suggesting the suitability of breath measurements for estimating exposure in the home; (4) limited data obtained on two additional chemicals-toluene and methylene chloride-indicated that both were prevalent at fairly high concentrations and that indoor air concentrations exceeded outdoor concentrations by a factor of about three.

Adolescent↗
PubMed1989

Interaction of permanently charged chlorpromazine and dopamine analogs with the striatal D-1 dopaminergic receptor.

Although a structural feature common to all dopaminergic agonists and antagonists is a side-chain basic amino group, it is unclear whether this moiety binds to the D-1 dopamine (DA) receptor in the charged or uncharged form. To obtain information on this point, we synthesized permanently charged dimethylsulfonium and quaternary ammonium analogs of chlorpromazine and DA and determined whether these compounds can bind to the D-1 receptor by measuring their abilities to inhibit the binding of SCH 23390, a D-1 receptor antagonist. Chlorpromazine and the dimethylsulfonium and trimethylammonium analogs of chlorpromazine were found to inhibit the binding of [3H]SCH 22390, which was maximally inhibited to the same extent by all three compounds. In addition, inhibition curves for the compounds fit a one-site binding model, indicating binding to a single class of sites. However, while the permanently charged chlorpromazine analogs were able to inhibit [3H]SCH-23390 binding, they were considerably less potent than chlorpromazine. DA and dimethyl DA were also able to inhibit [3H]SCH 23390 binding. However, the permanently charged dimethylsulfonium and trimethylammonium analogs of DA were ineffective in inhibiting [3H]SCH 23390 binding. In addition, the permanently uncharged methylsulfide analog did not inhibit binding. These studies show that permanently charged analogs of chlorpromazine can bind to the striatal D-1 receptor, which is consistent with an anionic recognition site on the D-1 receptor that interacts with antagonists in the cationic form. In addition, it appears that a nitrogen atom is not required for binding to the D-1 receptor, since the sulfonium analog of chlorpromazine bound to the receptor to the same extent as chlorpromazine. However, since the permanently charged or uncharged analogs of DA did not bind to the D-1 receptor, it is still unclear as to whether the charged form of a dopaminergic agonist can bind. The lower potency or ineffectiveness of the permanently charged analogs compared to the parent amines (chlorpromazine, DA, dimethyl DA) in binding to the D-1 receptor may reflect the inability of the permanently charged analogs to undergo hydrogen binding with the anionic site of the receptor.

Animals↗
PubMed1989

Oligoclonal immunoglobulins in HIV infection.

We tested 150 patients infected with human immunodeficiency virus (HIV) for the presence of oligoclonal bands in serum, prompted by reports that these abnormal proteins may have prognostic significance. Sixty HIV-negative individuals from "at-risk" groups were tested along with 80 HIV-negative, healthy blood donors for the presence of these bands. All sera were tested by isoelectric focusing, because it is more sensitive for this purpose than more-conventional electrophoretic techniques. In the HIV-positive group, 61% of the sera had oligoclonal bands; in the HIV-negative "at-risk" group, 36% had bands. No bands were detectable in sera from the healthy blood-donor group. Some patients were also followed for differing periods throughout their infection, and changes in their oligoclonal banding patterns could not be correlated with disease progression. The fact that oligoclonal bands were found to be present without HIV infection in a substantial number of individuals from within the "at-risk" groups leads us to conclude that the presence of oligoclonal bands in HIV infection is of limited prognostic significance.

HIV Seropositivity↗
PubMed1988

Interaction of permanently uncharged dopamine analogs with the D-2 dopaminergic receptor.

The purpose of this study was to determine if structural analogs of dopamine in which the side chain nitrogen has been replaced by a permanently uncharged monomethylsulfide, monomethylselenide or sulfoxide group are capable of binding to the striatal D-2 dopamine receptor and acting as agonists at this receptor. All the permanently uncharged dopamine analogs were found to bind to the D-2 dopamine receptor as evidenced by their abilities to inhibit significantly [3H]spiperone binding to striatal homogenates. However, the inhibition of [3H]spiperone binding by the uncharged dopamine analogs was incomplete and was almost abolished by the addition of NaCl (125 mM) to the incubation medium or by the addition of dopamine or quinpirole at a concentration that that saturates the high-affinity state of the D-2 dopamine receptor. These effects of NaCl, dopamine and quinpirole suggest that the uncharged dopamine analogs bind primarily to the high-affinity state of the D-2 dopamine receptor. Whether the uncharged monomethylsulfide and sulfoxide analogs could function as dopamine agonists at the striatal D-2 dopamine receptor was assessed by determining the abilities of these compounds to inhibit the K+-evoked release of [3H]acetylcholine from striatal slices. Both the monomethylsulfide and sulfoxide analogs inhibited the K+-evoked release of [3H]acetylcholine, but this inhibitory effect does not appear to be due to the activation of the D-2 dopamine receptor since it was not reversed by the selective D-2 dopamine antagonist, sulpiride. Additionally, the uncharged monomethylsulfide and sulfoxide dopamine analogs were found to antagonize the ability of apomorphine to inhibit the K+-evoked release of [3H]acetylcholine, but this antagonistic effect does not appear to be due to the reversible blockade of the D-2 dopamine receptor since it was not reduced by increasing the concentration of apomorphine. Therefore, while the permanently uncharged analogs of dopamine appear to bind to the high-affinity state of the D-2 dopamine receptor, they are not dopamine agonists or antagonists at the striatal D-2 dopamine receptor involved in regulating the release of acetylcholine. These results suggest that a positive charge may be a requirement for the activation of the striatal D-2 dopamine receptor.

Acetylcholine↗
PubMed1988

In vitro T cell responses to a candidate Epstein-Barr virus vaccine: human CD4+ T cell clones specific for the major envelope glycoprotein gp340.

Specific T cell proliferation was observed in short-term blood mononuclear cell cultures set up from Epstein-Barr virus (EBV)-immune individuals and challenged either with UV-irradiated EB virions or with a candidate subunit vaccine preparation, the purified envelope glycoprotein gp340 incorporated into immune stimulating complexes (gp340 iscoms). Limiting dilution culture of the activated T lymphoblasts in interleukin 2-containing medium generated stable CD3+CD4+CD8- T cell clones. Particular clones showing virus-specific proliferation in preliminary screening assays were selected for more detailed study. Three gp340 iscoms-induced clones from EBV-immune donor CG responded specifically to restimulation either with UV-EBV or with purified gp340 iscoms in the presence of autologous antigen-presenting cells (APC). Both T cell-depleted blood mononuclear cells and the EBV-transformed B cell line (treated with Acyclovir to block endogenous gp340 production) could be used for presentation, the latter being the more efficient when gp340 iscoms was the source of antigen. Blocking studies with monoclonal antibodies to HLA class II antigens and experiments using HLA-typed allogeneic APC indicated that all three gp340-specific CG clones were restricted through the HLA-DR2 antigen. One gp340 iscoms-induced clone from another EBV-immune donor, MR, likewise showed gp340-specific proliferation, in this case restricted through a HLA-DR4 antigen. Using HLA-DR-homozygous B cell lines representing the five known DR4 subtypes, efficient presentation of gp340 to this T cell clone was observed with both DR4 Dw4 and DR4 Dw14 antigens. Parallel experiments on one UV-EBV-induced T cell clone from donor MR gave a different pattern of results; these cells appeared to be specific for a virus structural component other than gp340 and to be restricted through an HLA-DP determinant.

Antibodies, Viral↗
PubMed1987

Interaction of permanently charged analogs of dopamine with the D-2 dopaminergic receptor.

Dopamine can exist in both charged and uncharged forms at physiological pH. At present it is unclear which of these forms is responsible for dopaminergic agonist activity. The purpose of this study was to determine whether permanently charged structural analogs of dopamine containing either a nitrogen, sulfur, or selenium atom in the side chain can bind to and activate the D-2 dopamine receptor. Binding to and activation of the D-2 dopamine receptor were measured by determining the abilities of the permanently charged dopamine analogs to inhibit [3H]spiperone binding to striatal homogenates and to inhibit K+-stimulated [3H]acetylcholine release from striatal slices respectively. The quaternary ammonium, dimethylsulfonium and dimethylselenonium analogs of dopamine were all found to inhibit [3H]spiperone binding to the same extent and in a manner qualitatively similar to the parent amines, dopamine and dimethyldopamine. Thus, [3H]spiperone inhibition curves for dopamine, dimethyldopamine and the permanently charged dopamine analogs were generally shallow and fit best to a two-site binding model as indicated by computer-assisted analyses. The addition of 125 mM NaCl to the incubation medium resulted in a significant decrease in the proportion of high affinity binding sites for both the permanently charged analogs and the parent amines. Similarly, the permanently charged dopamine analogs were found to maximally inhibit the K+-stimulated release of [3H]acetylcholine to the same extent as dopamine and dimethyldopamine. However, the permanently charged analogs were less potent in inhibiting both [3H]spiperone binding and K+-stimulated [3H]acetylcholine release than dopamine and dimethyldopamine. These results show that dopamine analogs possessing a permanent positive charge in the side chain can bind to and activate the D-2 dopamine receptor. The lower potencies of the permanently charged analogs in binding to and activation of the D-2 dopamine receptor suggest that, while the ability of a compound to exist in an uncharged form is not a requirement, both charged and uncharged forms of the agonist molecule appear to play a role in D-2 dopamine agonist activity.

Acetylcholine↗
PubMed1986

Homologous recombination in a Chinese hamster X-ray-sensitive mutant.

We have tested the mutant Chinese hamster cell line xrs-5, which is sensitive to ionizing radiation, for the ability to carry out homologous recombination. In an in vivo assay to detect recombination between two transfected plasmids carrying non-complementing mutants in the neomycin resistance gene, xrs-5 showed a 6-fold reduction in recombination frequency when compared to the parental cell line K1. Extracts prepared from nuclei of the mutant were also tested for their ability to catalyze homologous recombination between the same two plasmids in vitro. Extracts from xrs-5 were found to mediate recombination in this assay at frequencies not significantly different from those obtained with extracts from the parental cell line.

Animals↗
PubMed1986

Transfection and homologous recombination involving single-stranded DNA substrates in mammalian cells and nuclear extracts.

We have examined the ability of single-stranded DNA to participate in homologous recombination reactions in mammalian cells and nuclear extracts derived from them. We have inserted a fragment of the neo gene into the single-stranded DNA phage vector M13 mp11. The neo fragment was derived from a deletion derivative of the prokaryotic-eukaryotic shuttle vector pSV2neo. The resulting single-stranded DNA was mixed with a double-stranded deletion derivative of pSV2neo and tested for recombination in human cells, monkey cells, and nuclear extracts obtained from human cells. We were able to obtain recombinant molecules containing wild-type neo genes in all three systems. Examination of the products of recombination indicated that they resulted from correction of the deletion in the double-stranded DNA substrate. We were unable to detect any extensive conversion of single-stranded DNA into its double-stranded counterpart before it participated in the recombination reaction. We have also tested the ability of single-stranded DNA to yield transfectants. When a single-stranded DNA derivative of the herpes simplex virus thymidine kinase (TK) gene was introduced into mouse L-M(TK-) cells, we were able to obtain TK+ colonies. From these results, we conclude that single-stranded DNA can participate in transfection as well as homologous recombination reactions in mammalian cells.

Animals↗
PubMed1986

Concentrations of 20 volatile organic compounds in the air and drinking water of 350 residents of New Jersey compared with concentrations in their exhaled breath.

Twenty volatile organic compounds were measured in the personal air and drinking water of 350 New Jersey residents in the fall of 1981. Two consecutive 12-hour integrated personal air samples and two tap water samples were collected from each participant. At the end of the 24-hour monitoring period, each participant supplied a sample of exhaled breath. Simultaneous outdoor samples were collected in 100 residential locations in two cities. Eleven compounds were present much of the time in air, but only four (the trihalomethanes) in water; wide ranges of exposures (three to four orders of magnitude) were noted for most compounds. Ten of 11 compounds displayed significant correlations between air exposures and breath concentrations; the 11th (chloroform) was correlated with drinking water exposures. It was concluded that breath measurements are a feasible, cost-effective, and highly sensitive way to determine environmental and occupational exposures to volatile organic compounds.

Air Pollutants↗
PubMed1986

Contribution of organic particulates to respiratory cancer.

This paper presents some of the issues that remain to be resolved in order to assess the risk of cancer related to exposure to organic particulates. Most reviews of the effects of organic particulates from the outdoor environment on the risk of lung cancer show that this source seems to play a minor role. However, as fuel use and chemical composition of air pollutants change, the contribution of outdoor pollution as a cause of cancer may also change. Indoor air pollution is a more important source of exposure to organic particulates than is outdoor exposure. Although there is clear evidence that in occupational settings organic particulates cause human cancer, there has been almost no study of exposure to these types of particulates within indoor settings. Previous research has focused on cigarette smoke as the major indoor pollutant, but more specific characterization of contaminants in both the workplace and the home is required. The health effects of the higher levels of some of these contaminants in the workplace should be evaluated and the results extrapolated to populations exposed to lower levels in the home. Extensive research is needed to characterize organic particulate mixtures appropriately and test them for carcinogenicity. Studies on the health risks of nitropolynuclear aromatic hydrocarbons and polychlorinated dibenzodioxins and dibenzofurans are reviewed, but their contribution to the overall burden of respiratory cancer in humans cannot be estimated at this time. Characterization of mixtures, assessment of exposures, and linkage of exposures to health effects are the objectives of the recommendations proposed for further research.

Air Pollutants↗