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R J Richards

Publications and source records attributed to R J Richards.

At least 55 records · Page 3Linked to original sources
PubMed1993

The accumulation of pentamidine and the toxic effects of the drug, its selected analogues and metabolites on isolated alveolar cells.

Radiolabelled [3H]pentamidine is accumulated into 48-h and 7-day cultures of alveolar epithelial type 2 cells and alveolar macrophages in a linear, time and dose-dependent manner, with the rate of uptake being 15.3, 13.4 and 17.9 pmol/micrograms protein per 30 min, respectively. Uptake was not affected by metabolic inhibitors. The differential toxicity of the parent drug pentamidine, five analogues and six metabolites was assessed on freshly isolated and type 2 cells maintained in culture over 24 h. Toxicity, determined by the attachment ability of alkaline phosphatase positive cells containing lamellar bodies was greater in freshly isolated cells. Overall, three/four of the analogues proved less damaging to type 2 cells than the pentamidine with one derivative [1,3-bis(4-amidino-2-methoxy)propane], a compound particularly efficacious against pneumocystis in rats, showing minimal toxicity. Five metabolites (chain hydroxylated derivatives) were less toxic than the parent drug. However, one metabolite (N,N-dihydroxy derivative) was much more toxic than pentamidine to both type 2 cells and alveolar macrophages. It is concluded that as the type 2 cell can accumulate the drug, it represents a target cell which is particularly sensitive to pentamidine and/or some of its metabolites.

Alkaline Phosphatase↗
PubMed1993

Dose-dependent distribution of 3H-pentamidine following intra-tracheal administration to rats.

1. The acute toxicity to the lung, and disposition, of pentamidine isethionate as a function of a pulmonary-delivered dose was investigated in the rat. 2. Acute toxicity 24 h following intra-tracheal instillation of pentamidine was determined by analysis of acellular surface protein concentration and differential cell counting of bronchoalveolar lavage fluid. These two parameters indicated that pentamidine doses > 10 mg/kg lead to increasingly severe oedematous and inflammatory responses within the lung. 3. Following intra-tracheal administration of sub-toxic doses of 3H-pentamidine (0.2-10 mg/kg), the extent of activity in liver, kidney, gut and lavage fluid at 24 h correlated significantly with dose, whereas the level of activity in lung was saturated at doses > 0.8 mg/kg. 4. Values of << 1 for liver:lung and kidney:lung ratios of 3H-activity at low pentamidine doses demonstrated the high affinity of the lung for the compound. These ratios substantially increased with pentamidine dose, reflecting distribution of the drug to liver and kidney. Association of radioactivity with these organs was rapid (< 30 min), and indicated that pentamidine is effectively absorbed from the respiratory tract following intra-tracheal instillation.

Animals↗
PubMed1993

Agenesis of the gallbladder in symptomatic adults. A case and review of the literature.

Agenesis of the gallbladder, with normal bile ducts, is a rare congenital condition occurring in 13 to 65 per 100,000 population, probably from failure of the gallbladder bud to develop or vacuolize in utero. Adults are usually asymptomatic. We report a 40-year-old woman with gallbladder agenesis, found at operation for presumed gallbladder disease. We review 44 similar cases: dyspepsia was the predominant symptom in 15 of 44 patients (34%); 24 of 44 (54%) had symptoms suggestive of biliary colic, and 12 of 44 (27%) had jaundice. Common duct stones were found in eight of 12 patients who were jaundiced, but not in any other. A familial tendency was reported in five series. Our patient and one other had another congenital anomaly. Ultrasound was performed on five patients: three had a small, shrunken gallbladder and in two the gallbladder was absent. Ultrasound may suggest the diagnosis if absence of the gallbladder is demonstrated in conjunction with another congenital anomaly.

Adult↗
PubMed1992

The accumulation of pentamidine into rat lung slices and its interaction with putrescine.

The aromatic diamidine, pentamidine, accumulated into rat lung slices by an uptake system that obeyed saturation kinetics, with an average Km value of 554 microM and a Vmax value of 4077 nmol/g lung wet wt/30 min, respectively. This system was not inhibited by metabolic inhibitors but was greatly diminished by lowering the temperature from 37 degrees to 4 degrees. Both compounds, pentamidine and putrescine, inhibited the uptake of the other and the inhibition of pentamidine accumulation by putrescine was demonstrated to be non-competitive. Uptake of putrescine was inhibited by increasing concentrations of pentamidine. As putrescine accumulates in epithelial type 1 and type 2 cells and in Clara cells, it is likely that pentamidine is also accumulated in these cell types but does not utilize the pulmonary uptake system for polyamine transport. Within the time period studied, toxic effects of the drug were not observed.

Animals↗
PubMed1992

Steroid hormones during puberty: racial (black-white) differences in androstenedione and estradiol--the Bogalusa Heart Study.

A large biracial cross-section of 1038 healthy children aged 6-18 yr with 519 blacks, 519 whites, 678 males, and 360 females was evaluated for Tanner stage and serum levels of androstenedione, dehydroepiandrosterone-sulfate, estradiol, progesterone, and testosterone. The anthropometric values of the blacks and whites were very similar at each Tanner stage with only minor differences in age, height, and weight related to an earlier onset of puberty in blacks. The hormones dehydroepiandrosterone-sulfate, progesterone, and testosterone did not exhibit any racial differences. Estradiol showed a significantly higher level among black males compared to white males (P less than or equal to 0.05) whereas androstenedione was significantly higher in both white males (P = 0.0001) and females (P less than or equal to 0.01) compared with blacks. Many hormones are known to effect insulin resistance and others have reported a correlation between insulin levels and androstenedione. Blacks suffer disproportionately from diabetes. Since puberty is a time of dramatic changes in insulin resistance, racial (black-white) differences in steroid hormone changes were explored. This study shows that a racial difference in androstenedione levels exist during puberty, at a time when racial differences in insulin resistance are becoming manifest.

Adolescent↗
PubMed1991

Diamine uptake by rat lung type II cells in vitro.

Lung epithelial type II cells are responsible for synthesising and secreting pulmonary surfactant which reduces surface tension and prevents lung collapse. Type II cells replace type I cells and can proliferate in response to alveolar injury. An important aspect of this proliferation may be the ability of type II cells to accumulate amines actively, particularly the endogenous diamine putrescine. Putrescine is accumulated into isolated alveolar type II cells by an energy-dependent process. The uptake obeys saturation kinetics for which an apparent Km of 14.7 microM and Vmax of 130 pmol/micrograms DNA/hr was derived. The inhibitory effects of structurally similar amines on putrescine accumulation are described. As the herbicide paraquat has been suggested to share the same uptake system as putrescine from lung slice studies, this phenomenon was investigated in type II cell cultures. The results demonstrated that paraquat is a partially competitive inhibitor of putrescine accumulation in the cells. The Ki for the inhibition of putrescine uptake by paraquat in type II cells was calculated to be 69 microM, a value which closely matches the Km for paraquat (70 microM) predicted from lung slice studies. In molecular terms, the partial nature of the competition indicates that paraquat and putrescine do not occupy identical sites. Saturation of its site by paraquat reduced the affinity of putrescine 3.6-fold, but did not abolish it.

Animals↗
PubMed1991

Biochemical and cellular mechanisms of pulmonary fibrosis.

This review summarizes the manner in which a variety of agents may induce fibrogenic reactions in the lung. The extent of reaction is dependent on dose, time scale of exposure, and chemical reactivity. The regime of multiple dosing with chemicals or gases with recovery periods is important in disease progression. The means by which biochemists and histopathologists assess fibrosis, the advantages and disadvantages of each of the methods as related to subjectivity, quantitation, and speed of analysis are compared. The mechanisms which control the step from fibrogenesis (a potentially reversible reaction) to fibrosis (irreversible) may be linked to the maturation of collagen, calcification, or the formation of cross-linked protein masses. Attention is given to hydroxylysine cross-links in newly formed "fibrotic" collagen but focusses on gamma-glutamyl-epsilon-lysyl cross-links formed by calcium-dependent transglutaminases. It is suggested that these enzymes, released by replacement epithelial cells, could be responsible for the formation of stabilized protein masses in the lung, thus contributing to a progressive fibrosis.

Animals↗
PubMed1990

The efficacy of triclabendazole and other anthelmintics against Fasciola hepatica in controlled studies in cattle.

In eight controlled tests 274 cattle were used to assess the efficacies of triclabendazole, albendazole, clorsulon, nitroxynil, oxyclozanide and rafoxanide against Fasciola hepatica. Against one-, two- and four-week-old early immature fluke the mean efficacies of triclabendazole given orally at 12 mg/kg were 88.1, 95.3 and 90.7 per cent, respectively. Clorsulon, nitroxynil and rafoxanide administered at recommended dose rates showed negligible activity against these stages of the parasite. Against six- and eight-week-old infections the mean efficacies of triclabendazole at 12 mg/kg were 87.5 per cent and 95.7 per cent, respectively. Against F hepatica aged six weeks, albendazole and oxyclozanide showed no activity and clorsulon, nitroxynil and rafoxanide had only slight to moderate activity. The efficacies of triclabendazole, clorsulon, nitroxynil and rafoxanide against 10- or 12-week-old parasites were 100, 99.0, 99.1 and 90.1 per cent, respectively. Albendazole and oxyclozanide showed poor efficacy against 12-week-old infections.

Administration, Oral↗
PubMed1990

Interactions between paraquat, endogenous lung amines' antioxidants and isolated mouse Clara cells.

The ability of paraquat to damage mouse lung Clara cells in the presence and absence of herbicide inhibitors is investigated using a cell culture system. Clara cell damage is assessed on the loss of nitroblue tetrazolium reductase activity and the inability to attach and spread on an extracellular matrix. Endogenous amines such as putrescine and spermidine reduce paraquat-induced damage at low concentrations indicating that they compete for the same cell surface receptor as paraquat and thus potentially block the accumulation of the herbicide. The efficacy of 10 microM exogenous putrescine as a protectant is reduced the longer the time before it is added to the cultures. Clara cells contain high levels of NADPH-dependent P-450 reductase which is required to redox cycle the paraquat and generate reactive oxygen radicals. Compounds with antioxidant properties are examined for their ability to reduce the Clara cell damage. Cystamine, the disulphide form of the naturally occurring thiol, cysteamine, and taurine, a metabolite of cystamine, both of which are accumulated in the lung, do not reduce paraquat-induced Clara cell damage. Another antioxidant, alpha-tocopherol is also ineffective but reduced glutathione (GSH), present in high quantities (3.2 mM) in clara cells, could reduce damage to the cultured cells. Cysteine, a precursor of GSH, can also prevent Clara cell damage when the concentration of paraquat is low.

Animals↗
PubMed1990

Can the blood urea nitrogen/creatinine ratio distinguish upper from lower gastrointestinal bleeding?

We wanted to know if the blood urea nitrogen to creatinine (BUN/Cr) ratio could help distinguish upper from lower gastrointestinal bleeding. We analyzed retrospectively patients admitted to our hospital for gastrointestinal bleeding over the past 5 years. A total of 126 patients represented 74 upper bleeds and 52 lower bleeds. The mean BUN/Cr ratio was significantly higher in upper than lower bleeders, 34.8 and 17.8 respectively (p less than 0.001). No lower bleeder had a ratio of greater than or equal to 36, whereas 38% of upper bleeders had a ratio of greater than or equal to 36. The BUN/Cr ratio may be an easy, cheap method of distinguishing upper from lower gastrointestinal bleeding in some cases. A BUN/Cr ratio of greater than or equal to 36 suggests upper gastrointestinal bleeding, whereas a ratio of less than 36 is not helpful in locating the source of bleeding.

Adult↗
PubMed1990

Isolation of Clara cells from the mouse lung.

A method is described for isolating Clara cells from the mouse lung that does not require the technique of elutriation. Mouse lungs totally perfused of blood are instilled with crystalline trypsin (0.25%) and incubated for the optimum time of 15 min. The lung tissue is chopped, mechanically agitated, and sequentially filtered to obtain a primary digest of 3 to 5 x 10(6) cells. Clara cells, identified routinely by histochemical localization of NADPH diaphorase, using the stain nitrotetrazolium blue (NBT), accounts for between 20 to 40% of the cells in the primary digest. Layering the cells of the primary digest on a discontinuous Percoll gradient followed by centrifugation gives rise to a major band of cells, 52% that are Clara cells (0.77 +/- 0.28 x 10(6)/mouse). A second method was devised to purify the Clara cells by simply centrifuging (32g, 6 min, 10 degrees C) the primary digest and discarding the supernatant that contained only a few NBT positive cells. When this process was repeated three times, the final pellet contained 68% Clara cells realizing 0.55 +/- 0.16 x 10(6) cells/mouse. The cells have typical Clara cell morphology as confirmed by electron microscopy and have a high level of P-450 enzymes (7-ethoxycoumarin deethylase and coumarin hydroxylase). Furthermore, the primary digests and the purified isolates contain less than 1% alveolar Type II cells, although such cells, identified by the histochemical localization of alkaline phosphatase, can be obtained by a second, more extensive digestion procedure. The simple procedure described for the isolation of mouse Clara cells could be further advanced if methods could be devised to prevent the loss of NADPH diaphorase activity during enzymatic digestion and cell centrifugation.

Animals↗
PubMed1990

Type II pneumocytes in mixed cell culture of human lung: a light and electron microscopic study.

Alveolar Type II epithelial cells dedifferentiate rapidly in vitro. Studies with animal tissue suggest that cell-cell and extracellular matrix-cell interactions are important in the retention of Type II cell morphology in vitro. Thus, in this study with human tissue, alveolar Type II cells, alveolar macrophages, and spindle cells were prepared from the same sample of lung (obtained following lobectomy for cancer, n = 3), cocultured on glass cover slips or tissue culture plastic, and studied by light microscopy with scanning (SEM) and transmission (TEM) electron microscopy for 8 days. The primary cell isolates contained approximately 45% Type II cells; the remainder were macrophages or unidentifiable cells. Clusters, made up of a single layer of cuboidal Type II cells around a central core of connective tissue (largely collagen and some elastic tissue), formed above a monolayer of spindle cells. The Type II cells were morphologically similar to those seen in vivo. The cells were still cuboidal at 8 days but had lost their lamellar bodies, which were released into the medium via the apical surface. The clusters increased in size with time (area, microns 2: day 1, 29(5-143) x 10(2); day 8, 63(10-311) x 10(2); mean(range); p less than 0.02) without changing in number per culture, suggesting Type II cell proliferation. This may have been due to factors produced by the other cells and adherence to the extracellular matrix (ECM); (free collagen fibers, present in the original preparation, spindle cells, and/or Type II cells could be responsible for presence of ECM). We propose this as a useful model for the study of human Type II epithelial cells in vitro.

Cell Differentiation↗
PubMed1990

Clara cell cultures from the mouse and their reaction to bronchiolar toxins.

The major aim of this study was to determine if small numbers of freshly isolated mouse Clara cells could be used to rapidly screen the toxic effects of a number of diverse pulmonary toxins. A short-term (20 hr) culture of functionally competent (nitotetrazolium reductase positive) Clara cells was developed. In this culture the Clara cells were allowed to attach to an extracellular matrix in 96-well multiwell plates containing a culture medium of DCCM 1 and Ultroser G (0.4%). Pulmonary toxins (a total of 26 agents with concentrations ranging from 10(-7) M to 10(-3) M) were examined for their ability to reduce the attachment efficiency of functionally competent Clara cells and TD50 values (the amount of toxin required to reduce normal attachment efficiency by 50%) were calculated. With the possible exception of some halogenated hydrocarbons, the simple toxicity test in vitro correlated well with the known effects of the bronchiolar necrotic agents in vivo. For 13 compounds studied there was a direct correlation between TD50 values in vitro and LD50 values (mostly oral) in rodents in vivo, the correlation coefficient of the regression line being 0.783.

Animals↗
PubMed1989

The biochemical and pathological changes produced by the intratracheal instillation of certain components of zinc-hexachloroethane smoke.

Zinc chloride which is formed by igniting a mixture of zinc oxide and hexachloroethane in the production of white smokes has been shown to produce oedema when given to rats as a single instillation. The oedematous reaction, as assessed by histopathology and measurements of alveolar surface protein in lavage fluid, is variable, dose-dependent, and maximal at 3 days but at sub-lethal doses it regresses after 7 days. The parent compound, zinc oxide, does not produce these effects. In some animals there is evidence of a fibrogenic response at 7 days post-exposure although it is currently unknown whether or not this effect is progressive.

Animals↗
PubMed1989

Actinomycosis: a rare cause of vesicocolic fistula.

We present a case of actinomycosis presenting as a vesicocolic fistula. There are no other such reported cases. The diagnosis, pathogenesis, and treatment of abdominal actinomycosis are reviewed.

Actinomycosis↗