Daphnia need to be gut-cleared too: the effect of exposure to and ingestion of metal-contaminated sediment on the gut-clearance patterns of D. magna

The presence of sediment particles in the gut indicated that Daphnia magna used in whole-sediment bioassays ingest sediment. If gut contents are not removed prior to whole-body tissue-burden analysis, then the bioavailability of any sediment-associated contaminants (e.g. metals) can be overestimated. Gut clearing patterns were determined for D. magna after exposure to both clean and metal-contaminated (Cu and Zn) field-collected sediments. D. magna exposed to reference sediment had fuller guts than those exposed to metal-contaminated sediment (95% versus 60% full). Neither reference- nor metal-exposed D. magna could clear their gut completely of sediment particles when held in clean water for 24 h. When Daphnia were transferred to clean water after exposure to metal-contaminated sediment, there was no significant decrease in gut-fullness (P>0.05) even after 48 h of purging. By comparison, animals transferred to water containing 5 x 10(5) cells of algae (Pseudokircheriella subcapita) after exposure to contaminated sediment showed a significant drop in gut fullness from 56% immediately after exposure to 17% after 4 h of gut-clearance. Although gut fullness did not change significantly beyond 2 h of purging, data were much less variable after 8 h of gut-clearance than after 2 h or 4 h. The depuration of Cu was well described with a two-compartment first-order kinetic model (r2=0.78, P<0.0001) indicating that D. magna exposed to metal-contaminated sediment have one pool of Cu that is quickly depurated (0.2 h(-1)), and one that has been incorporated into the tissues (<<0.00001 h(-1)). Assuming tissue background of 48 microg/g, an exposed animal which has not been depurated or which has been purged with water alone would yield whole-body tissue Cu concentrations that are 5.6- and 4-fold higher, respectively, than that purged with algae + water (8 h). We recommend that D. magna used to estimate metal bioavailability from sediment be gut-cleared in the presence of algae for 8 h prior to determination of whole-body metal concentrations.

Inhalation toxicity of dimethyl piperidinone

A mixture of 1,3-dimethyl-2-piperidinone and 1,5-dimethyl-2-piperidinone (DMPD) (approximately 63-37 parts by weight) was tested for its inhalation toxicity in rats following 90-day repeated exposures. Male and female rats were exposed whole-body to either 0, 51, 230, or 310 mg/m(3) DMPD for 6 h/day, 5 days/weak for 90 days. Clinical signs, growth, clinical pathology, tissue pathology, neurobehavior, neuropathology, and semen quality were evaluated. No compound-related adverse effects were noted in clinical signs, body weights, food consumption, clinical laboratory evaluations, neurobehavioral evaluations, neuropathology, or sperm counts. Laryngeal changes consisting of minimal squamous epithelial hyperplasia and degeneration/necrosis of the cartilage were present in male and female rats exposed to 310 mg/m(3) both immediately following exposure and after the 1-month recovery period Male rats exposed to DMPD had increased relative kidney weights, increased formation of hyaline droplets and granular casts, and increased incidence of chronic progressive nephropathy. These kidney effects are consistent with increased accumulation of the urinary protein alpha(2 mu)-globulin, which has been well essential for several xenobiotics. The subsequent increased incidence of progressive nephropathy was specific to male rats with the alpha(2 mu) syndrome. Male and female rats exposed to 230 or 310 mg/m(3) had centrilobular hepatocellular hypertrophy, and male rats exposed to 310 mg/m(3) had increased relative liver weights. These liver changes were reversible following the recovery period and were considered not to represent adverse toxicological effects of treatment. Since the male rat-specific renal findings do not connote adversity for man and are net considered relevant to human hazard assessment, the no-observed-effect level in male and female rats was 230 mg/m(3), based on the microscopic changes in the larynx exposed to 310 mg/m(3).

Cell biology of laryngeal epithelial defenses in health and disease: preliminary studies

Esophageal epithelium has intrinsic antireflux defenses, including carbonic anhydrases (CAs I to IV) that appear to be protective against gastric reflux. This study aimed to investigate the expression and distribution of CA isoenzymes in laryngeal epithelium. Laryngeal biopsy specimens collected from the vocal fold and interarytenoid regions were analyzed by Western blotting and immunofluorescence. Carbonic anhydrases I and II were expressed by the majority of samples analyzed. In contrast, CA III was differentially expressed in the interarytenoid samples and was not detected in any vocal fold samples. The expression of CA III was increased in esophagitis as compared to normal esophageal tissue. Carbonic anhydrase I and III isoenzymes were distributed cytoplasmically in the basal and lower prickle cell layers. The laryngeal epithelium expresses some CA isoenzymes and has the potential to protect itself against laryngopharyngeal reflux. Laryngeal tissue may be more sensitive to injury due to reflux damage than the esophageal mucosa because of different responses of CA isoenzymes.

Further considerations of the skeletal system as a biomarker of episodic chlorpyrifos exposure

The mummichog, Fundulus heteroclitus, is a common inhabitant of eastern seaboard estuaries. As such, it can be affected by coastal agricultural and other nonpoint source runoff. We examined the effects of short-term episodic exposures to an agricultural pesticide, chlorpyrifos, on brain acetylcholinesterase (AChE) activity and vertebral yield strength in lab-reared and wild-caught fish. Brain AChE activity was chosen as an indicator because it is the target system for organophosphate action. Vertebral yield strength was chosen as an indicator because previous research warranted further investigation (Karen et al., 1998). Four daily or weekly 6 h exposures (2.5, 5.0, and 10.0 microg/l chlorpyrifos) in decreased salinity seawater (5 g/kg) significantly reduced brain AChE activity. The lowest concentration was within the range of reported environmental chlorpyrifos concentrations; thus inhibition of brain AChE from environmental chlorpyrifos exposures may pose a hazard to estuarine organisms. Yield strength measured in lab-reared fish appeared to be more sensitive to episodic chlorpyrifos exposures, because chlorpyrifos was a significant factor in 75% (3 out of 4) of tests performed with lab-reared fish. Chlorpyrifos exposure was a significant factor in only 25% (1 out of 4) tests performed with wild fish. These results suggested that changes in the responses of bone to load testing, following several short exposures to an organophosphate, could be sensitive indicators in lab-reared organisms.

Toxicity of pesticides to aquatic microorganisms: a review

Microorganisms contribute significantly to primary production, nutrient cycling, and decomposition in estuarine eco-systems; therefore, detrimental effects of pesticides on microbial species may have subsequent impacts on higher trophic levels. Pesticides may affect estuarine microorganisms via spills, runoff, and drift. Both the structure and the function of microbial communities may be impaired by pesticide toxicity. Pesticides may also be metabolized or bioaccumulated by microorganisms. Mechanisms of toxicity vary, depending on the type of pesticide and the microbial species exposed. Herbicides are generally most toxic to phototrophic microorganisms, exhibiting toxicity by disrupting photosynthesis. Atrazine is the most widely used and most extensively studied herbicide. Toxic effects of organophosphate and organochlorine insecticides on microbial species have also been demonstrated, although their mechanisms of toxicity in such nontarget species remain unclear. There is a great deal of variability in the toxicity of even a single pesticide among microbial species. When attempting to predict the toxicity of pesticides in estuarine ecosystems, effects of pesticide mixtures and interactions with nutrients should be considered. The toxicity of pesticides to aquatic microorganisms, especially bacteria and protozoa, is an area of research requiring further study.

Toxicity of pesticides to aquatic microorganisms: a review

Microorganisms contribute significantly to primary production, nutrient cycling, and decomposition in estuarine eco-systems; therefore, detrimental effects of pesticides on microbial species may have subsequent impacts on higher trophic levels. Pesticides may affect estuarine microorganisms via spills, runoff, and drift. Both the structure and the function of microbial communities may be impaired by pesticide toxicity. Pesticides may also be metabolized or bioaccumulated by microorganisms. Mechanisms of toxicity vary, depending on the type of pesticide and the microbial species exposed. Herbicides are generally most toxic to phototrophic microorganisms, exhibiting toxicity by disrupting photosynthesis. Atrazine is the most widely used and most extensively studied herbicide. Toxic effects of organophosphate and organochlorine insecticides on microbial species have also been demonstrated, although their mechanisms of toxicity in such nontarget species remain unclear. There is a great deal of variability in the toxicity of even a single pesticide among microbial species. When attempting to predict the toxicity of pesticides in estuarine ecosystems, effects of pesticide mixtures and interactions with nutrients should be considered. The toxicity of pesticides to aquatic microorganisms, especially bacteria and protozoa, is an area of research requiring further study.

Toxicity of tetrafluoroethylene and S-(1,1,2, 2-tetrafluoroethyl)-L-cysteine in rats and mice

Groups of 25 female F344 rats and 25 female B6C3F1 mice were exposed to 0, 30, 300, 600, or 1200 ppm tetrafluoroethylene (TFE) by inhalation for up to 12 days. Another set of 25 female rats and 25 female mice of the same strains were given 0, 5, 20, or 50 mg/kg of S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFE-CYS) by oral gavage for 12 days. Both 12-day exposure regimens consisted of exposures for 5 consecutive days, a weekend with no exposures, and 4 consecutive daily exposures following the weekend. Five animals per group were sacrificed after the first exposure, the fifth exposure, and the ninth exposure for evaluation of cell proliferation in the liver and kidney. The remaining animals in each group (up to 10) were sacrificed after the ninth exposure (test day 12) for pathological evaluation of the liver, kidney, and spleen. Clinical pathology evaluations were performed on test day 11 or 12. Inhalation of TFE by rats and mice caused slight microscopic changes in the kidneys of rats and mice, but no histopathological changes in the liver. In the kidney, administration of TFE-CYS by gavage caused severe microscopic changes in rats, moderate-to-severe changes in mice, and no microscopic changes in the liver. Cell proliferation was increased in the kidneys of rats and mice given TFE by inhalation and TFE-CYS by gavage. TFE-CYS also caused increased liver weights and cell proliferation in the liver of rats and mice at the high doses. The cell proliferation response in the kidney and liver was transient in both species, being most pronounced after 5 days of exposure, and less evident or absent after 12 days of exposure. In the kidney, the cell proliferation and histopathologic response in rats was generally more pronounced than in mice. Kidney damage and cell proliferation were confined to the pars recta (P3) of the outer stripe of the outer medulla and medullary rays. Tubules in mice exposed to TFE and TFE-CYS had mostly regenerating cells by test day 12, while in rats the tubules still showed marked degeneration along with regeneration by the end of the study. The cortical labyrinth (P1 and P2 segments) was also affected at the 50 mg/kg dose of TFE-CYS in rats. Rats exposed to 50 mg/kg TFE-CYS had a mild anemia, and rats exposed to 1200 ppm TFE had slight, biologically inconsequential decreases in erythrocyte mass that may have been compound-related. In spite of the rather pronounced histopathologic changes in the kidneys of rats exposed to TFE-CYS, there was no clinical chemistry evidence for decreased kidney function. Increased levels of urinary fluoride were present in rats exposed to 300 ppm and greater of TFE, and in rats exposed to 20 and 50 mg/kg TFE-CYS. The spleen was not affected in this study. Overall, the results of this study suggest that effects of TFE could be attributed to the toxicity of TFE-CYS over the course of a 2-week exposure, as all effects that were seen with TFE were also seen with TFE-CYS.

Fluid phase endocytosis in oral epithelia: variation with site and effect of cancer

The structure of the oral mucosa has been extensively studied but its cell physiology has been less well characterised. This study aimed to show the range in variation in fluid phase endocytic capability in biopsies from different oral sites. Oral epithelial cells were obtained from both biopsies and single-cell suspensions obtained by brushing the oral cavity. Biopsies in organ culture and single cells in suspension were incubated with fluorescent microspheres of 0.02, 0.1 or 1.0 microm diameter. Endocytosis of fluorescent microspheres was quantitated by flow cytometry and visualised by confocal microscopy. Epithelial cells from all oral sites that were sampled internalised 0.02 microm and 0.1 microm but not 1.0 microm microspheres, with no significant differences observed between oral regions. Single cells from non-cancer patients endocytosed significantly more 0.02 microm microspheres than cells removed from patients with oral cancer. This model may be used to study integrated oral cell function both in health and disease.

Starting young: improving the health and developmental outcomes of infants and toddlers in the child welfare system

The number of infants and toddlers entering out-of-home care has increased dramatically in the past few years, yet few published reports examine their needs. This article describes a collaborative, multidisciplinary developmental follow-up program for infants and toddlers that builds on the community-based family support model described in the Family to Family Foster Care Reform Initiative. The children's health and developmental status, as well as the program's effectiveness, are highlighted.

Fluid phase endocytosis within buccal mucosal cells of alcohol misusers

The structure of the oral mucosa is now well characterised, although studies on oral epithelial cell function have received less attention. The aims of this study were to see whether endocytosis could be demonstrated in cells from oral smears and if so, to assess the effect of chronic high alcohol intake on such uptake. Buccal mucosal smears were collected from 135 patients (91 non- or social drinkers, and 44 patients with harmful alcohol use). Name, age, sex, and alcohol history (for alcohol problem patients) were recorded. Cell suspensions were incubated in a solution of bovine serum albumin (BSA)-coated fluorescently labelled latex microspheres (0.02 micron diameter) in Ham's F-10 culture medium for 1 h at 37 degrees C as a marker of fluid phase endocytosis. Uptake of microspheres was confirmed by confocal microscopy, and mean endocytosed fluorescence levels determined by flow cytometry. A repeat smear from 11 of the alcohol patients was taken 9-14 days later. Endocytosis was significantly reduced in both male (P < 0.01) and female (P < 0.01) alcohol problem patients compared to controls. Units of alcohol consumed and cigarettes smoked per day did not show a dose-response correlation with endocytosis in the alcohol problem patients. Apparent abstinence from alcohol had no further effect on endocytic uptake at days 9-14. This study shows that normal oral squamous cells removed as buccal smears readily endocytose fluorescent microspheres and that this capacity can be affected by alcohol. Chronic high alcohol intake would appear to down regulate endocytosis in buccal cells even up to 14 days of abstinence. This may have implications for the pathogenesis of oral mucosal disorders in long-term users.

Biochemical and morphological correlations in human gallbladder with reference to membrane permeability

There is good evidence that gallbladder epithelium is permeable to a diverse range of molecules which move into the epithelial cell from the lumen or the basement membrane. Morphological investigations have shown both secretory mucous droplets, components of the endocytosis pathway together with evidence of a system allowing passage of molecules across the basement membrane. This indicates that the gallbladder epithelium may be influenced by molecules presented via the apical and basal membranes, complicating our understanding of gallbladder function, particularly in disease. Gallbladder disease increases the proteoglycan content of the basement membrane, but the implication of this in terms of permeability remains to be defined. Indeed, it remains unknown whether this precedes disease or is a manifestation of the disease process. The removal of water from hepatic bile by gallbladder involves two counter ion transport systems. Autoradiography shows that ion transport occurs into the lateral intracellular spaces but it remains unclear whether this leads to a hypertonic solution in these spaces causing an osmotically driven water absorption or if the process involves an osmotically linked isotonic secretion. These ion pumps are reversible, for water is absorbed during the interdigestive phase but fluid is secreted into the lumen during digestion or in the presence of disease. Appropriate neural stimulation can increase or decrease fluid absorption from the lumen while vasoactive intestinal peptide or secretin promote fluid secretion, probably mediated by prostaglandins leading to raised cyclic AMP acting at the cellular level. Immediate control may depend on intracellular Ca2+ which activates a calmodulin-protein kinase, phosphorylating the counter ion transporters to downregulate their activity. Failure of this regulatory process may explain the initial increase in bile concentrating potential seen in the development of gallstones although the mechanism of such failure remains unknown. More concentrated bile increases movement of biliary compounds into gallbladder epithelial cells which alter gallbladder function in a complex manner. Secondary bile acids are raised in gallstone disease and increase permeability of the gallbladder epithelium to molecules including cholesterol. This cholesterol absorbed from the lumen may have paramount importance to gallbladder function. Raised biliary cholesterol reduces gallbladder motility, possibly by increasing the amount of cholesterol in gallbladder muscle membranes and reducing contraction in response to cholecystokinin. However, increased secondary bile acids are also associated with an alteration in phospholipid acyl groups which may alter ion transport activity and/or cholesterol solubility within the micelle/vesicle. As the acyl groups show increased arachidonate levels the production of prostaglandins could be raised, although currently it is not known if this phospholipid arachidonate enters the epithelial cells. In addition, gallbladder inflammation is associated with raised phospholipase A2 activity, leading to formation of fatty acids and lysophospholipid which causes membrane damage. The fatty acids are likely to displace cholesterol from the micelle but may also act directly on the epithelium, possibly increasing prostaglandin production and thus stimulating mucin secretion. Increased mucin secretion is seen early in gallstone disease but the evidence presently available cannot determine if this is a causative factor.

Dynamics of ATP-induced calcium signaling in single mouse thymocytes

Extracellular ATP (ATPo) elicits a robust change in the concentration of intracellular Ca2+ ([Ca2+]i) in fura-2-loaded mouse thymocytes. Most thymocytes (60%) exposed to ATPo exhibited a biphasic rise in [Ca2+]i; [Ca2+]i rose slowly at first to a mean value of 260 nM after 163 s and then increased rapidly to a peak level of 735 nM. In many cells, a declining plateau, which lasted for more than 10 min, followed the crest in [Ca2+]i. Experiments performed in the absence of extracellular [Ca2+]o abolished the rise in thymocyte [Ca2+]i, indicating that Ca2+ influx, rather than the release of stored Ca2+, is stimulated by ATPo. ATPo- mediated Ca2+ influx was potentiated as the [Mg2+]o was reduced, confirming that ATP4- is the active agonist form. In the absence of Mg2+o, 3'-O-(4-benzoyl)benzoyl-ATP (BzATP) proved to be the most effective agonist of those tested. The rank order of potency for adenine nucleotides was BzATP4->ATP4->MgATP2->ADP3-, suggesting purinoreceptors of the P2X7/P2Z class mediate the ATPo response. Phenotyping experiments illustrate that both immature (CD4-CD8-, CD4+CD8+) and mature (CD4+CD8-, CD4-CD8+) thymocyte populations respond to ATP. Further separation of the double-positive population by size revealed that the ATPo-mediated [Ca2+]i response was much more pronounced in large (actively dividing) than in small (terminally differentiated) CD4+CD8+ thymocytes. We conclude that thymocytes vary in sensitivity to ATPo depending upon the degree of maturation and suggest that ATPo may be involved in processes that control cellular differentiation within the thymus.

Hepatic and adrenal changes in rabbits associated with hyperlipidemia caused by a semi-synthetic diet

Several investigators have reported that feeding a semi-synthetic diet of casein and dextrose to New Zealand White (NZW) rabbits will increase total serum cholesterol concentration, principally through an increase in the beta-lipoprotein fractions, thereby creating a useful model for atherosclerosis research. Although there is evidence to suggest that the dextrose/casein diet alters low-density lipoprotein receptor and bile acid clearance of cholesterol, the underlying mechanism is not completely understood. The effects of the diet on the overall physiology of the rabbit have received little attention. In this study feeding a diet of casein and dextrose of male NZW rabbits for 4 weeks resulted in changes in the serum lipid concentrations. During that time the rabbits fed the dextrose/casein diet gained less weight than did control rabbits. In the test diet rabbits, liver aspartate and alanine transaminase activities were increased from baseline values of 27 +/- 2 U/L and 89 +/- 9 U/L respectively to 112 +/- 21 U/L and 281 +/- 34 U/L respectively, then returned to the high end of the reference range. Necropsy findings included hepatomegaly caused by vacuolar hepatopathy in 19 or 20 experimental rabbits; rabbits fed the control diet had no hepatic lesions. Ultrastructural analysis revealed that enlargement of the liver cells was due to glycogen deposition. Adrenal glands from animals fed the experimental diet had a minimal change in the size of the adrenocortical cells consisting of slight ballooning and rarefaction of the cytoplasm. In a second study the level of dietary fiber was doubled. This resulted in a three-fold increase in lipid concentrations, compared with the fivefold increase in the first study. The liver enzyme activities were increased to the same extent as in the first study. Histologic changes were comparable to those in the first study. The activity of hepatic cholesterol 7alpha-hydroxylase was 3.7 +/- 0.4 pmol/min/mg of protein, compared with the control value of 7.7 +/- 1.1 pmol/min/mg of protein (P < 0.05) in the second study. The improved rate of weight gain and the lesser increase in total serum cholesterol concentration in the second study with increased dietary fiber suggest that two separate activities may be involved. Although the level of dietary fiber may be related to weight gain and total serum cholesterol values, the relation to the decrease in liver transaminase activities in study 1 was probably coincidental. It appears that the dextrose/casein diet causes decreased activity of hepatic cholesterol 7alpha-hydroxylase, which could cause a decrease in the biliary excretion of cholesterol.

Endocytosis of fluorescent microspheres by human oesophageal epithelial cells: comparison between normal and inflamed tissue

This paper examines the presence and characteristics of endocytosis by oesophageal epithelial cells. Biopsy specimens from normal and inflamed oesophagus were incubated in organ culture with fluorescent microspheres (0.1 and 0.01 microns diameter). These markers were taken into early endosomes and the lysosomes of both the smaller differentiating prickle cells and the larger mature squamous cells. Confocal and electron microscopy showed that markers passed to the early endosomes and the lysosomes by endocytosis. The process was energy dependent. Larger, 1 micron microspheres adhered to the epithelial cells but were not phagocytosed. Disaggregated cells were analysed by flow cytometry. Microspheres were endocytosed in proportion to the concentration in the culture medium in a dose dependent manner. Cells from inflamed oesophagus were significantly smaller (p = 0.013) and took up significantly more microspheres than cells from normal biopsy specimens (p = 0.015). In conclusion, endocytosis occurs in oesophageal epithelial cells and is increased in inflammation.

Ca2+ influx pathways mediated by swelling or stores depletion in mouse thymocytes

We used fura-2 video imaging to characterize two Ca2+ influx pathways in mouse thymocytes. Most thymocytes (77%) superfused with hypoosmotic media (60% of isoosmotic) exhibited a sharp, transient rise in the concentration of intracellular free Ca2+ ([Ca2+]i). After a delay of approximately 70 s, these swelling-activated [Ca2+]i (SWAC) transients reached approximately 650 nM from resting levels of approximately 100 nM and declined from a time constant of 20 s. Peak [Ca2+]i during transients correlated with maximum volume during swelling. Regulatory volume decrease (RVD) was enhanced in thymocytes exhibiting SWAC transients. Three lines of evidence indicate that Ca2+ influx, and not the release of Ca2+ from intracellular stores, underlies SWAC transients in thymocytes. First, thymocytes swollen in Ca2+-free media failed to respond. Second, Gd3+ and La3+ inhibited SWAC influx with Kd's of 3.8 and 2.4 microM, respectively. Finally, the depletion of Ca2+ stores with thapsigargin (TG) before swelling did not inhibit the generation, nor decrease the amplitude, of SWAC transients. Cell phenotyping demonstrated that SWAC transients are primarily associated with immature CD4-CD8- and CD4+CD8+ thymocytes. Mature peripheral lymphocytes (mouse or human) did not exhibit SWAC transients. SWAC influx could be distinguished from the calcium release-activated Ca2+ (CRAC) influx pathway stimulated by store depletion with TG. In TG-treated thymocytes, [Ca2+]i rose steadily for approximately 100 s, peaked at approximately 900 nM, and then declined slowly. Simultaneous activation of both pathways produced an additive [Ca2+]i profile. Gd3+ and La3+ blocked Ca2+ entry during CRAC activation more potently (Kd's of 28 and 58 nM, respectively) than Ca2+ influx during SWAC transients. SWAC transients could be elicited in the presence of 1 microM Gd3+, after the complete inhibition of CRAC influx. Finally, whereas SWAC transients were principally restricted to immature thymocytes. TG stimulated the CRAC influx pathway in all four thymic CD4/CD8 subsets and in mature T cells. We conclude that SWAC and CRAC represent separate pathways for Ca2+ entry in thymocytes.

Chronic toxicity/oncogenicity of dimethylformamide in rats and mice following inhalation exposure

The potential chronic toxicity and oncogenicity of dimethyl-formamide (DMF) was evaluated by exposing male and female rats and mice to 0, 25, 100, or 400 ppm DMF for 6 hr/day, 5 days/week for 18 months (mice) or 2 years (rats). Clinical pathology was evaluated at 3, 6, 12, 18, and 24 (rats only) months. An interim euthanasia for rats occurred at 12 months and hepatic cell proliferation in rats and mice was examined at 2 weeks, 3 months, and 12 months. No compound-related effects on clinical observations or survival were observed. Body weights of rats exposed to 100 (males only) and 400 ppm were reduced. Conversely, body weights were increased in 400 ppm mice. No hematologic changes were observed in either species. Serum sorbitol dehydrogenase activity was increased in rats exposed to 100 or 400 ppm. There were no compound-related effects on the estrous cycle of rats or mice at any concentration. Compound-related morphological changes were observed only in the liver. In rats, exposure to 100 and 400 ppm produced increased relative liver weights, centrilobular hepatocellular hypertrophy, lipofuscin/hemosiderin accumulation in Kupffer cells, and centrilobular single cell necrosis (400 ppm only). In mice, increased liver weights (100 ppm males, 400 ppm both sexes), centrilobular hepatocellular hypertrophy, accumulation of lipofuscin/hemosiderin in Kupffer cells, and centrilobular single cell necrosis were observed in all exposure groups. These observations occurred in a dose-response fashion and were minimal at 25 ppm. No increase in hepatic cell proliferation was seen in mice or female rats. Slightly higher proliferation was seen in male rats exposed to 400 ppm at 2 weeks and 3 months but not at 12 months. Dimethylformamide was not oncogenic under these experimental conditions in either the rat or mouse.

Development and evaluation of a sexual history-taking curriculum for first- and second-year family practice residents

BACKGROUND

Primary care physicians need to assess their patients' sexual behaviors to help prevent, diagnose, and treat sexually transmitted diseases. However, few physicians take sexual histories. We developed an educational curriculum aimed at increasing the frequency with which our residents take sexual histories from patients.

METHODS

Residents were observed for 5 months through video monitoring of patient encounters to document the precurriculum rate of taking sexual histories. Residents also completed a sexuality questionnaire about the likelihood of encountering certain patient problems and the residents' degree of comfort and competence with these problems. They then completed the educational curriculum and were monitored for 3 months for any change in taking sexual histories. We added follow-up telephone interviews with the residents to determine the effect of the curriculum and the extent of taking sexual histories.

RESULTS

Due to insufficient data collected with video monitoring in the postcurriculum phase, we used telephone interviews to evaluate the curriculum. Prior to the curriculum, only 7% of the residents reported routinely asking patients about their sexual history, compared to 36% of residents 6 months after implementation of the curriculum.

CONCLUSION

The sexual history-taking curriculum improved the frequency with which residents collected information from patients on sexual activity. In addition, this article addresses the development of the curriculum based on a needs assessment, and the difficulties in and possible solutions to evaluating curricular changes within family practice residency programs.

Membrane chloride conductance and capacitance in Jurkat T lymphocytes during osmotic swelling

Video microscopy and whole-cell patch-clamp recording were used to monitor changes in relative cell volume (V/Vo), chloride conductance (gCl), and membrane capacitance (Cm) during osmotically induced swelling in Jurkat T lymphocytes. Cellular swelling was initiated with hyperosmotic pipette solutions. Simultaneous evaluation of V/Vo and gCl revealed a 59-s delay between the inception of swelling and the activation of outwardly rectifying, ATP-dependent Cl- channels. Following the delay, increases in V/Vo and gCl progressed in parallel. In contrast, Cm, a measure of cell surface area, fell gradually at a rate of approximately 150 fF/min after whole-cell access was achieved. The decline in Cm lasted 200 s and was followed by a rapid rise (approximately 750 fF/min). The rise in Cm coincided with a variable increase in "leak" current, gCl increased at a slower rate and reached lower peak values in experiments performed without ATP; ATP had no effect on the biphasic Cm time course. The temporal separation of conductance and capacitance during swelling suggests that gCl and Cm vary independently, supporting the hypothesis that a large portion, if not all, of the whole-cell Cl- conductance activated during swelling is provided by volume-sensitive Cl- channels preexisting in the plasma membrane.

Chloride channels activated by osmotic stress in T lymphocytes

We have used whole-cell and perforated-patch recording techniques to characterize volume-sensitive Cl- channels in T and B lymphocytes. Positive transmembrane osmotic pressure (intracellular osmolality > extracellular osmolality) triggers the slow induction of a Cl- conductance. Membrane stretch caused by cellular swelling may underlie the activation mechanism, as moderate suction applied to the pipette interior can reversibly oppose the induction of Cl- current by an osmotic stimulus. Intracellular ATP is required for sustaining the Cl- current. With ATP-free internal solutions, the inducibility of Cl- current declines within minutes of whole-cell recording, while in whole-cell recordings with ATP or in perforated-patch experiments, the current can be activated for at least 30 min. The channels are anion selective with a permeability sequence of I- > SCN- > NO3-, Br- > Cl- > MeSO3- > acetate, propionate > ascorbate > aspartate and gluconate. GCl does not show voltage- and time-dependent gating behavior at potentials between -100 and +100 mV, but exhibits moderate outward rectification in symmetrical Cl- solutions. Fluctuation analysis indicates a unitary chord conductance of approximately 2 pS at -80 mV in the presence of symmetrical 160 mM Cl-. The relationship of mean current to current variance during the osmotic activation of Cl- current implies that each cell contains on the order of 10(4) activatable Cl- channels, making it the most abundant ion channel in lymphocytes yet described. The current is blocked in a voltage-dependent manner by DIDS and SITS (Ki = 17 and 89 microM, respectively, at +40 mV), the degree of blockade increasing with membrane depolarization. The biophysical and pharmacological properties of this Cl- channel are consistent with a role in triggering volume regulation in lymphocytes exposed to hyposmotic conditions.

Cholesterol absorption by the gall bladder

Model and real biles were used to investigate factors influencing cholesterol and dextran (70,000 molecular weight) absorption by the gall bladder. Cholesterol absorption was proportional to cholesterol concentration when real bile was used, but model biles showed maximal absorption at cholesterol saturation. Reduction of temperature reduced cholesterol absorption and serosal secretion, but had little effect on dextran absorption. This indicates differences in uptake where cholesterol undergoes passive diffusion but dextran is taken up by fluid-phase endocytosis. Model bile prepared with a single bile salt showed lowest cholesterol uptake from cholate bile, but there was no difference in serosal secretion. Dextran uptake was also lowest from cholate bile, although serosal secretion was highest. These results show that an increase in the biliary content of dihydroxy bile salts increases gall bladder permeability to both hydrophobic and hydrophilic molecules and may lead to the accumulation of lipids in the mucosa, as seen in cholesterolosis.

Inhalation toxicity study of formamide in rats

Formamide is a widely used solvent for the manufacture and processing of plastics, and the possibility for inhalation exposure exists for workers. To assess the toxicity of repeated inhalation of sublethal concentrations of formamide, three groups of 10 male Crl:CD BR rats each were exposed nose-only for 6 hr/day, 5 days/week for 2 weeks to design concentrations of 100, 500, or 1500 ppm of formamide vapor in air. A control group of 10 male rats was exposed simultaneously to air only. At the end of the exposure period, blood and urine samples were collected for clinical analyses, and 5 rats per group were killed for pathologic examination. The remaining 5 rats per group were retained for a 14-day postexposure observation (recovery) period and then subjected to the same clinical and pathologic examinations. Male rats exposed to 1500 ppm had significantly depressed body weights and body weight gains during the exposure and recovery periods compared to controls. Clinical pathologic examinations revealed that decreased platelet and/or lymphocyte counts were observed in rats exposed to 500 or 1500 ppm of formamide. Pathologic examinations revealed compound-related microscopic changes in the kidneys of rats exposed to 1500 ppm formamide. Minimal to severe necrosis and regeneration of renal tubular epithelial cells were observed principally in the outer stripe of the outer medulla and in cortical medullary rays. Based upon the hematologic and clinical chemical parameters measured, the no-observed-effect exposure concentration for repeated inhalation of formamide was considered to be 100 ppm, under the conditions of this study. The findings of treatment-related microscopic lesions in the kidneys as well as increases in mean absolute kidney weights and kidney-to-body weight ratios reflect the target organ toxicity.

Identification of octadeca-9,11-dienoic acid and its significance in the diagnosis of cervical intraepithelial neoplasia

In 1987 it was claimed using high performance liquid chromatography (HPLC) that the molar ratio of octadeca-9,11-dienoic acid to its parent linoleic acid (18:2 (9,12)) was raised in malignant and premalignant conditions of the cervix. In this study based on a gas chromatographic procedure which prevents autoxidation and avoids the detection limitations of HPLC, we have shown that assay of these fatty acids has no role to play in the assessment of cervical neoplasia.

The effect of secretin on sodium ion absorption by the isolated human gallbladder

Sodium ion (Na+) transport, a principal function of the gallbladder epithelium, was studied by measuring the flux of 22Na across isolated human gallbladder mucosa maintained in a modified 'Ussing' flux chamber. Tissue was obtained from cholecystectomy specimens in symptomatic patients with cholelithiasis. Out of 26 gallbladders studied, 13 had a net Na+ flux from mucosa to serosa which indicated active Na+ absorption. The hormone secretin, when added to the serosal fluid, reversed the direction of net flux in these gallbladders and caused a secretion of Na+ from serosa to mucosa. These results suggest that secretin may be involved in the physiological regulation of fluid transport in the human gallbladder, and also suggest a possible role for this hormone in gallbladder emptying.

Purification of bacteriorhodopsin and characterization of mature and partially processed forms

Bacteriorhodopsin (BR) essentially free of native lipids has been prepared in a highly stable state. Purple membrane was solubilized in Triton X-100 and BR was purified by size exclusion chromatography using 3-[cholamidopropyl)dimethylammonio]-2-hydroxyl-1-propanesulfonic acid (CHAPSO) detergent at pH 5. Molar ratios of phospholipid/BR ranged from 0.4 to 0.05 corresponding to 94-98% phospholipid removal. Purified BR has an absorbance ratio (A280nm/A548nm) of 1.5-1.6 in the dark-adapted state which is the highest purified BR/protein ratio reported to date. The purified BR in CHAPSO shows maximum stability in the pH range 5.0-5.5. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of native purple membrane and solubilized BR from most Halobacterium halobium JW-3 cultures show 3 higher molecular weight bands in addition to BR. Immunological staining and amino acid sequencing indicates that these additional proteins are partially processed forms of the BR precursor protein. The BR preprotein contains 13 additional amino acids on the NH2 terminus which are removed by post-translational processing in at least four steps. Isoelectric focusing separated most delipidated and non-delipidated BR samples into 8 bands. Incomplete BR post-translational processing BR is thought to be largely responsible for the multiplicity of isoelectric BR species. The principal components have pI values of 5.20 and 5.24 and both have absorption maxima at 550 nm, characteristic of detergent-solubilized BR. BR in Triton X-100 or nonylglucoside, delipidated BR in CHAPSO, and BR in intact purple membrane all have a dark-adapted ratio of 13-cis to all-trans-retinal of 1.9:1.

Isoelectric focusing studies of bacteriorhodopsin

Purified bacteriorhodopsin (BR) samples show a minimum of four isoelectric forms in immobilized pH gradient isoelectric focusing gels. The bands occur as doublets with isoelectric points (pI) centered at 5.20 (principal species) and 5.60. In typical preparations additional bands may be observed at 4.90, 5.07 and 5.50. Purple membrane (PM) was proteolyzed with papain to calibrate the pI shift produced by changing the number of charges on the protein. Asp-242 is removed during the first cleavage between residues 239 and 240 resulting in the loss of a single negative charge and a shift of the principal doublet by +0.35 pH units to pI 5.55. The second papain cleavage occurs between residues 231 and 232 which removes Glu-232, -234 and -237 and shifts the pI by +0.60 pH units to pI 6.10. The +0.60 pH shift upon the second papain cleavage is consistent with the loss of two negative charges and is supported by prior evidence that at least one of the three glutamate residues lost during the second proteolysis step is protonated and neutral in the intact protein. The native and proteolyzed products of BR retain the characteristic 550 nm absorption maxima for solubilized BR. A model for the structural origin of the pI heterogeneity of BR species in proteolyzed PM is presented.

Studies on the mechanism of non-visualization of diseased human gallbladders during oral cholecystography

Oral cholecystography is a well established method for studying the human gallbladder and radiological non-visualization of the gallbladder has been shown to correlate highly with the presence of disease. The exact mechanism by which diseased gallbladders fail to visualize is unclear, but may be due to a failure of the gallbladder to concentrate the luminal contents. Concentration of gallbladder contents is achieved by the reabsorption of water, the driving force for which is active sodium (Na+) absorption. Therefore Na+ transport was studied by measuring the flux of Na22 across isolated human gallbladder mucosa (obtained at cholecystectomy) and compared with the results of oral cholecystography and histological grading. In 27 gallbladders studied, 59% absorbed Na+, whilst the remainder secreted Na+. Comparison with histological grading showed that as gallbladders became more diseased they absorbed less Na+ and were more likely to secrete Na+. In addition, gallbladders that absorbed Na+ were significantly more likely to visualize on cholecystography than those that secreted Na+. These results indicate that some diseased human gallbladders secrete, rather than absorb, Na+ and suggest that the mechanism for radiological non-visualization is failure of fluid absorption and the development of active fluid secretion.

Sodium transport in the diseased human gallbladder and the effects of indomethacin

1. Sodium ion (Na+) transport, a principal function of the gallbladder epithelium, was studied by measuring the flux of 22Na across isolated, inflamed human gallbladder mucosa maintained in a modified 'Ussing' flux chamber. Tissue was obtained from cholecystectomy specimens in symptomatic patients with cholelithiasis. 2. In 30 gallbladders studied, 57% had a net Na+ flux from mucosa to serosa (Na+ absorption), while 23% had a net Na+ flux from serosa to mucosa (Na+ secretion). The remaining 20% showed no overall net Na+ flux. 3. Indomethacin added to the serosal fluid reversed the direction of net Na+ flux in secreting gallbladders and caused an absorption of Na+. In Na+-absorbing gallbladders, indomethacin caused a slight reduction in Na+ absorption. No change in Na+ flux was induced in gallbladders with no initial net Na+ flux. 4. These results demonstrate that instead of absorbing Na+, some inflamed human gallbladders may secrete Na+. As this secretion can be reversed to the more usual absorption by indomethacin, it is likely that this secretion is mediated by prostaglandins.

Characteristics of cholesterol absorption by human gall bladder: relevance to cholesterolosis

The characteristics of cholesterol uptake by 83 human gall bladders (obtained at cholecystectomy) were studied with a modified Ussing technique. Real and artificial biles labelled with 14C-cholesterol and 3H-dextran (the latter to correct for adherent mucosal bile) were used; all gall bladders absorbed cholesterol (average 3.5 nmol/cm2/minute). Recovery of the absorbed cholesterol from the tissue showed that about 4% was esterified over 60 minutes. In artificial bile the rate of absorption of cholesterol increased as the bile saturation index rose, but became constant once supersaturation was achieved. In contrast, supersaturated real bile permitted greater absorption of cholesterol, possibly due to enhanced cholesterol solubilisation. Preincubation of gall bladder tissue in sodium cyanide (5 mM) caused a 30% reduction in cholesterol uptake indicating that, although absorption is predominantly a "passive" process, there is a partial "active" component. There were no pronounced differences in the rate of cholesterol absorption as gall bladders became more diseased, but there was a reduction in the amount of cholesterol ester formed.

Ligatin: a peripheral membrane protein with covalently bound palmitic acid

The ligatin monomer is a polypeptide of Mr = 10,000 which is soluble in acidified chloroform:methanol, a characteristic similar to that of Folch-Lee proteolipid. The hydrophobicity of ligatin is also reflected by its ability to interpolate into the phosphatidylcholine bilayer as shown by a concentration-dependent change in membrane conductance. However, unlike other proteolipids the amino acid composition of ligatin is not enriched in hydrophobic amino acids (isoleucine, leucine, valine, methionine, phenylalanine, tryptophan). Instead, the hydrophobic character of ligatin could be explained, at least in part, by the covalent association of fatty acids, 1.4-1.7 mol of palmitate/10,000 g of protein, as revealed by gas chromatography mass spectrographic analyses. The post-translational addition of fatty acid may therefore be the means by which ligatin acquires an affinity for membranes.

Effects of glucose or fructose feeding on glycogen repletion in muscle and liver after exercise or fasting

In athletics, muscle and liver glycogen content is critical to endurance. This study compared the effectiveness of glucose and fructose feeding on restoring glycogen content after glycogen was decreased by exercise (90-min swim) or fasting (24 h). After 2 h of recovery from either exercise or fasting there was no measurable glycogen repletion in red vastus lateralis muscle in response to fructose. In contrast, glucose feeding induced a similar and significant carbohydrate storage after both depletion treatments (8.44 mumol X g-1 X 2 h-1). In the liver, following 2 h of recovery, the rates of glycogen storage were similar after either glucose or fructose ingestion, but fasting caused a greater rate of repletion (83 mumol X g-1 X 2 h-1) than exercise (50 mumol X g-1 X 2 h-1). After 4 h of recovery fructose-fed exercised animals had the highest glycogen concentration (165 mumol X g-1) followed by the glucose-fed exercised group (119 mumol X g-1). These values were 50 and 36%, respectively, of that measured in the normal-fed liver (327 mumol X g-1). In contrast, liver glycogen values in the fasted group decreased between the 2nd and 4th hour of recovery in response to both feeding regimens. From these results we conclude that fructose is a poor nutritional precursor for rapid glycogen restoration in muscle after exercise, but that both glucose and fructose promote rapid accumulation of glycogen in the liver.

Biliary cholesterol--friend or foe?

It has hitherto been assumed that the cholesterol in bile simply represents an excretory mechanism for cholesterol surplus to bodily requirements. However, recent evidence suggests that this is not the case and that biliary cholesterol has other functions. The functions consist of a mucosal protective effect against the toxic action of bile-salts and also a role in regulating dietary cholesterol absorption. Biliary cholesterol is clearly more than just an excretory substance and serves other important physiological roles.

Effects of colchicine on the gallbladder of the mouse

The effects of colchicine on the mouse gallbladder followed a course depending on the dosage given (0.4-4 mg/100 g body weight). Following 0.5 mg/100 g, by 16 h there was a marked cholestasis with dilatation of the gallbladder and steatosis. There were progressive alterations in the Golgi apparatus and accumulation of vesicles. The apical mucous droplets decreased in number and became pleomorphic and dispersed throughout the cytoplasm. Lipid droplets appeared in numbers on the epithelial cytoplasm. By 48 h the tissues had reverted to normal appearances. When cholecystokinin, pilocarpine or ceruletide were given to animals which had received colchicine 18 h previously, the excess bile from the dilated gallbladder was discharged into the duodenum, remaining apical mucous droplets secreted and electron dense material accumulated in the lateral intercellular space. This formed a quasi-regular array between the epithelial bases and the basement membrane. Biochemically there was a significant decrease in alkaline phosphatase activity and a significant increase in acid phosphatase activity.

Cholesteryl esters in human gallbladder bile and mucosa

Cholesteryl esters, identified by thin-layer and gas-liquid chromatography followed by mass spectroscopy in a few cases, were found in all human bile samples analysed. The amount varied extensively both in absolute concentration and when expressed as a percentage of the total cholesterol present. In about 30% of samples, the percentage of ester exceeded 4% of total cholesterol but there was no clear association with the presence of cholesterol gallstones or pigment stones, nor was there any association with the lithogenicity of bile.

Hematological and bone marrow effects of ribavirin in rhesus monkeys

Ribavirin (Virazole, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), a broad-spectrum antiviral compound, was evaluated for effects on blood and bone marrow of rhesus monkeys when administered by intramuscular injection for 10 days in doses of 30 or 100 mg/kg/day (four monkeys/group). Both groups developed a normochromic, normocytic anemia that was mild in the low-dose group and severe in the high-dose group. A dose-related erythroid hypoplasia occurred during the treatment period. Myeloid precursors were not affected. Differential counts of erythroid precursors showed a significant decrease in late erythroid forms while early erythroid forms were either unchanged or increased. Megakaryocyte numbers were increased in both groups. Qualitative changes in marrow cells included vacuolization of erythroid precursors and of occasional white cell precursors and megakaryocytes, and the appearance of bone marrow histiocytes containing red cells in various stages of disintegration. Thrombocytosis occurred in both treatment groups, with platelet counts returning to control values after drug withdrawal. Platelet function was not affected by treatment. No drug-related changes were seen during the treatment period for total and differential leukocyte counts, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration. Reticulocyte counts and mean corpuscular volume increased after treatment then returned to control values. Osmotic fragility of erythrocytes was not changed. These data show that in monkey, ribavirin causes a dose-related decrease in circulating red blood cell mass that is due in part to suppression of late erythroid precursors in bone marrow. These effects are reversible when treatment is discontinued and are not predictive of potentially serious or lasting untoward effects of ribavirin.