A cholinergic interaction in alpha 2 adrenoceptor-mediated antinociception in sheep

Intraspinal administration of alpha 2 adrenergic agonists produces analgesia, but clinical application of these agents is limited by dose-dependent sedation and hypotension. Recently, neostigmine has been demonstrated to counteract hypotension in sheep and enhance antinociception to tail flick in rats from spinally administered alpha 2 adrenergic agonists. We investigated this spinal interaction further in chronically prepared, conscious sheep, testing antinociception with a mechanical pressure stimulus on the forelimb. Clonidine produced dose-dependent antinociception which was antagonized by idazoxan and enhanced by neostigmine, although it was unaltered by methylatropine. Clonidine increased acetylcholine in cerebrospinal fluid, an effect potentiated by physostigmine and blocked by idazoxan. The highly lipid-soluble alpha 2 adrenergic agonists dexmedetomidine and clonidine produced antinociception, whereas the poorly lipid-soluble ST-91 (2,[2,6-diethylphenylamino]-2-imidazoline) produced antinociception only at much larger doses and did not affect cerebrospinal fluid levels of acetylcholine. In human volunteers, epidurally administered clonidine increased cerebrospinal fluid acetylcholine levels at the time of peak analgesia. These results support the existence of an interaction between alpha 2 adrenergic and cholinergic mechanisms of analgesia at the spinal level and underscore the importance of lipid solubility in the actions of spinally administered drugs in sheep.

Neostigmine counteracts spinal clonidine-induced hypotension in sheep

BACKGROUND

Intraspinal clonidine injection produces analgesia free of respiratory depression, but also decreases blood pressure and causes sedation. Spinal neostigmine injection alone increases blood pressure in animals and enhances clonidine-induced analgesia.

METHODS

To test whether neostigmine would alter clonidine-induced hypotension, nine chronically prepared sheep received intrathecal injections of saline or neostigmine (150, 300, 1,000 micrograms) followed in 15 min by 200 micrograms clonidine.

RESULTS

Clonidine plus saline decreased mean arterial pressure by 12 +/- 3% associated with small, statistically nonsignificant decreases in heart rate, cardiac output, and systemic vascular resistance. Prior injection of neostigmine diminished hypotension 60 min after clonidine injection in a dose-dependent manner. To further define the time course and pharmacology of this interaction, seven other sheep received intrathecal saline, neostigmine (1,000 micrograms), or neostigmine plus methylatropine (1,000 micrograms) 75 min prior to 200 micrograms clonidine. With this longer interval between injections, neostigmine abolished clonidine-induced hypotension, and this protective effect was inhibited by methylatropine. To test whether rostral spread of neostigmine in cerebrospinal fluid would alter its hemodynamic effects, we injected intrathecal neostigmine into the upper cervical site. Intrathecal neostigmine increased mean arterial pressure and heart rate at this site to a degree similar to that in the thoracic area, with no effect on behavioral or arterial blood gas tensions.

CONCLUSIONS

These data are consistent with neostigmine's counteraction of clonidine-induced hypotension by a spinal muscarinic mechanism and support investigation of spinal alpha 2-adrenergic-cholinergic combinations for pain therapy.

Intrathecal clonidine and the response to hemorrhage

Intraspinally administered alpha 2-adrenergic agonists are being examined for postoperative analgesia, yet their effects on the hemodynamic response to acute hemorrhage have not been examined. In this study chronically prepared conscious sheep received thoracic intrathecal saline or clonidine 300 micrograms followed in 15 min by rapid removal of 1,000 ml blood. In saline-treated ewes blood pressure was maintained and heart rate steadily increased during hemorrhage of up to 700 ml blood, with further blood removal resulting in rapid decreases in both variables. In contrast, heart rate never increased and blood pressure was maintained only up to 400 ml blood loss in animals receiving intrathecal clonidine. Compared to saline controls, clonidine did not alter blood pressure or heart rate at the end of hemorrhage or during blood pressure restitution during the next hour. Clonidine inhibited the increase in plasma epinephrine at the end of hemorrhage without altering plasma norepinephrine, vasopressin, renin, or atrial natriuretic factor. Intrathecal idazoxan, a specific alpha 2-adrenergic antagonist, reversed clonidine's effect on blood pressure during hemorrhage. Intravenous DG-5128, a poorly lipid-soluble alpha 2-adrenergic antagonist, also reversed clonidine's effect and additionally completely blocked any reduction in blood pressure and heart rate during hemorrhage. These data suggest that intrathecal clonidine interferes with maintenance of blood pressure during hemorrhage, likely because of a spinal sympatholytic effect, but does not affect the ultimate decrease in blood pressure after rapid removal of 1,000 ml blood. This difference in effect during the two phases of hemorrhage can be explained by the relative importance of the sympathetic nervous system in each.

Vasopressin and fetal cerebrovascular regulation

Vasopressin (AVP) may increase cerebral blood flow (CBF) during hypoxemia by selective dilatation of cerebral vessels via endothelium-derived relaxing factor (EDRF) release. To test whether this action is relevant in the fetus, we produced isocapnic hypoxemia in halothane-anesthetized pregnant ewes. Fetal infusion of a V1 AVP antagonist reduced by 55% the increase in CBF during fetal hypoxemia. To test the role of this response during development, we examined the response to AVP in intact and endothelium-denuded femoral and basilar arterial rings in vitro from fetal, newborn, and adult sheep. AVP constricted femoral rings in an endothelium-independent manner, with increased potency in newborn and fetal compared with adult rings. AVP relaxed basilar rings in an endothelium-dependent manner, which was unaffected by indomethacin treatment, with increased potency in newborn and adult compared with fetal rings. We conclude that fetal cerebral vascular endothelium is functional and responsive to AVP and that circulating AVP during fetal hypoxemia contributes to increased CBF via this effect.

The vascular mechanism of ephedrine's beneficial effect on uterine perfusion during pregnancy

Sensitivity to the vasoconstricting actions of adrenergic agents is altered during pregnancy and is drug-, regional vascular bed-, and endothelium-dependent. To examine whether the uterine perfusion-sparing property of ephedrine is due to local actions, we examined the effects in vitro of ephedrine and the alpha-adrenergic agonist metaraminol (10(-10)-10(-3) M) in uterine and femoral vessels, with and without functional endothelium, from nonpregnant and pregnant ewes. Both agents produced dose-dependent contractions in all vascular rings. In all cases metaraminol was more potent (by analysis of the concentration producing a 50% maximal response [EC50]) and efficacious (by maximal effect). Pregnancy increased constriction from both agents in femoral arterial rings, whereas pregnancy decreased constriction from both agents in uterine arterial rings. However, the ratio of maximal effect at femoral versus uterine rings during pregnancy was greater for ephedrine (5.2 +/- 0.6) than metaraminol (1.9 +/- 0.3). This difference was further accentuated by endothelium removal. Constriction to both agents was abolished by phentolamine (10(-5) M). These data suggest that both ephedrine and metaraminol constrict uterine and systemic vessels by actions on alpha adrenoceptors, and that ephedrine may spare uterine perfusion during pregnancy due to more selective constriction of systemic vessels than that caused by metaraminol.

Mitral valve replacement: mechanical versus bioprosthetic valves--a clinical review

A review of the literature was conducted in an attempt to justify the exclusive use of either mechanical or tissue prostheses in the mitral position. In addition, the University of Toronto experience with mitral valve replacement was reviewed, including a five year follow-up from the Toronto General Hospital. Both studies concluded that there was no significant advantage for the use of either type of valve based upon freedom from thromboembolism, freedom from anticoagulant-related hemorrhage and freedom from all valve-related mortality/morbidity. Tissue valves were shown to be significantly poorer substitutes in terms of freedom from primary valve failure (P less than 0.05) and freedom from reoperation due to valve-related complications (P less than 0.07). The clinical results from the Toronto General Hospital correlated with those reported in the literature and suggested the preferential use of mechanical valves during mitral valve replacement based primarily on their durability and a consequent lesser need for reoperation.

Toxicity studies of butylated hydroxyanisole and butylated hydroxytoluene. I. Genetic and cellular effects

The cellular effects of the antioxidants butylated hydroxyanisole and butylated hydroxytoluene were studied in a battery of in vitro tests. No evidence of genotoxicity was obtained for either compound in the hepatocyte primary culture/DNA repair test, the Salmonella/microsome mutagenesis test, the adult rat liver epithelial cell/hypoxanthine guanine phosphoribosyl transferase test, or for butylated hydroxyanisole in the Chinese hamster ovary cell/sister chromatid exchange test. Both compounds inhibited intercellular molecular exchange between cultured liver cells, an effect that has been observed for many agents with neoplasm-promoting activity.

Hyperglycaemia after burn injury

The effect of burn injury on blood sugar levels, serum insulin levels and glucose tolerance was studied in male rats. In the burned group (following 50 per cent surface burn injury), the blood sugar level was significantly increased after burn injury in comparison with control uninjured rats. Hyperglycaemia was blocked by injection of phentolamine (10 mg/kg) for 24 h or propranolol (50 micrograms/kg) 30 min before burn or if the animals were adrenalectomized 4 days before injury. Serum insulin levels were significantly decreased in the scalded rats and their glucose tolerance was impaired. Early hyperglycaemia probably arises as a result of adrenal medullary hyperactivity. The initial rise in blood glucose probably arises from glycogen breakdown, followed later by increased hepatic production of glucose. The 50 per cent body surface scald injury is followed, acutely, by a period of glucose intolerance. In part, this intolerance may be due to decreased serum levels of insulin. The inadequate response of insulin secretion in response to glucose loading may be due to inhibition of insulin secretion by pancreatic beta cells caused by elevated catecholamine levels, possibly in combination with the action of antagonists such as glucagon, which may be secreted in excess as a result of stimulation by catecholamines.

Clinical performance of Bjork-Shiley mechanical heart valves: a perspective on outlet strut fractures in the 60 degrees and 70 degrees convexo-concave disc models

The convexo-concave disc model of Bjork-Shiley mechanical heart valve is a significant improvement over the spherical disc model and compares favourably to other valves, including bioprostheses, with respect to hemodynamics, thromboembolism, anticoagulant related hemorrhage and prosthetic endocarditis. A small number of the 60 degrees and 70 degrees welded outlet strut Bjork-Shiley convexo-concave valves are at risk of sudden structural failure. The risk is constant or decreasing with time. Elective explanation is not recommended. The integral outlet monostrut 70 degrees Bjork-Shiley convexo-concave valve demonstrates further improvements in design and durability, and is recommended for use in patients who are appropriate candidates for mechanical cardiac prostheses.

Clinical results of pericardial xenograft valves: the Ionescu-Shiley and Hancock valves

Between 1979 and 1985, 552 Ionescu-Shiley valves were implanted in 511 patients. The Hancock valve was implanted in 122 patients (129 valves) between 1982 and 1983. Sixty percent of procedures were isolated aortic valve replacements. In the Ionescu series, 59% of these were 19 or 21 mm valves while only 15% of the Hancock valves were of this size. For isolated mitral valve replacement, 76% of Ionescu-Shiley valves were 25 to 27 mm, compared to 36% of the Hancock valves. Patient age, sex, prior operations, concomitant surgery (usually coronary bypass), operative mortality and late deaths were similar for both valves. A mean follow-up of 38 months was obtained for each valve population (99% complete) representing a cumulative 1497 patient-years for the Ionescu-Shiley valve and 375.4 patient-years for the Hancock valve. Actuarial survival for the former was 73 +/- 4% at 72 months, and 65 +/- 14% for Hancock valves at 60 months. The frequency of major events during follow-up (thromboembolism, anticoagulant related hemorrhage, bland perivalvular leak and prosthetic valve endocarditis) were similar, but the frequency of primary tissue valve failure was markedly different for the two valves (1.1% per patient-year for Ionescu-Shiley valves and 5.9% for the Hancock valve). The mean interval to replacement of an Ionescu mitral prosthesis was significantly shorter (23.4 months) than for replacement of an aortic prosthesis (42 months) while the mean interval to replacement of an Ionescu aortic and/or a Hancock aortic or mitral were all similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Five-year follow-up of Hancock pericardial valves: management of premature failure

The durability and function of bovine pericardial valves are dependent upon design, preservation, patient factors (age, sex), and site of valve implantation. In 1983, a shelf recall of all Hancock bovine pericardial valves (HPV) was instituted by the manufacturer. This report represents the results of an organized 5-year follow-up in a hospital Prosthetic Valve Registry of 129 HPV implanted in 122 patients (79 males, 43 females) between May 1982 and April 1985 using echo Doppler and careful clinical evaluation. Mean age was 56 +/- 15 years. There were 81 AVR, 33 MVR, 7 DVR, and 1 TVR. Concomitant coronary bypass was performed in 38 patients (31%). Surgery was on a redo basis in 25 patients (20%), urgent in 14 (11%), and for SBE in 8 patients (7%). There were seven hospital deaths (5.7%). Mean follow-up was 44 months (maximum 66 months) for 114 patients (99% complete), representing 417 patient years. There have been 20 late deaths (18%), of which 7 were directly valve related. Linearized frequency of major events (per pt-yr) was: thromboembolism, 1.6%; anticoagulant related hemorrhage, 0.8% (1 late death); prosthetic valve endocarditis 1.3%; primary tissue failure, 5.8%. Patient symptomatology was a more accurate predictor of bioprosthetic failure requiring reoperation than echo Doppler studies, which were completed in 74 of 97 patients examined during scheduled follow-up visits. Twenty-four of the 96 patients (25%) have required re-replacement at a mean interval of 44 months (27-59 months) from initial implantation. This was due to vertical shear starting at the top of the strut anchoring commissural attachments in every case.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat liver foci and in vitro assays to detect initiating and promoting effects of chlorinated ethanes and ethylenes

Nine chlorinated aliphatics (CAs) were examined in a rat liver foci assay for tumor initiating and promoting activities. In this model, young adult male Osborne Mendel rats were first subjected to a partial hepatectomy, the test chemical was then administered at the maximum tolerated dose in the initiation or promotion phase in conjunction with diethylnitrosamine (DEN; 30 mg/kg b.w.) or phenobarbital (PB; 0.05 percent, w/w, in the diet), and gamma glutamyltranspeptidase (GGT) was used as a putative preneoplastic indicator. When administered in the promotion protocol after initiation with DEN, 1,1-dichloroethane, 1,1,2-trichloroethane (1,1,2-TCE), 1,1,2,2-tetrachloroethane (1,1,2,2-TTCE), tetrachloroethylene (TTCY), and hexachloroethane induced significant increases in GGT+-foci above control levels. 1,1,2,2-TTCE, TTCY, and 1,1,2-TCE also induced significant increases in GGT+-foci when administered in the promotion protocol without DEN initiation. Two variants of GGT+-foci were observed: the classical type associated with PB promotion, and the other, which was more diffuse, less intensely stained, resembling foci undergoing redifferentiation and associated with CAs. A number of CAs were also genotoxic in short-term in vitro tests. Taken together, the studies suggest that CAs may be complete carcinogens in vivo with weak initiating activity and stronger promoting activity.

Randomised controlled trial of computer assisted management of hypertension in primary care

The hypothesis that general practitioners would obtain better outcomes for patients with hypertension using a computer than doctors not using a computer was tested. Sixty family physicians were randomised to two treatment strategies. "Test" physicians completed a data collection form after each visit from a patient with hypertension and mailed the forms to the test centre for processing. Computer feedback on management was mailed to the doctors. This encouraged doctors to apply the "stepped care" protocol, supplied charts of diastolic blood pressure v time, and ranked patients' diastolic blood pressures by percentile. Letters were mailed to patients to remind them of appointments. "Control" doctors filled out the same data collection forms as test physicians, but neither doctors nor patients received computer feedback. Physicians who used the computer saw more patients per practice than control doctors (test 50 patients, control 40). For all patients the length of follow up was significantly longer in test practices (test 199 days, control 167), and a smaller percentage dropped out of active treatment in test practices (test 37.5%, control 42.1%). For patients with "moderate" hypertension of a baseline diastolic pressure of greater than 104 mm Hg the mean score of the last recorded pressure was below the goal of 90 mm Hg in test practices (88.5 mm Hg), but it failed to reach this goal in control practices (93.3 mm Hg). A greater average reduction of diastolic pressure was achieved in test practices (test 21.7 mm Hg, control 16.7 mm Hg). Though patients with "moderate" hypertension were better controlled in test practices than in control practices, the patients in test practices visited their doctors less often (test 13.3 visits per patient-year, control 17.4 visits). Among patients with newly detected hypertension test practices achieved a greater reduction in diastolic pressure than control practices (test 15.1 mm Hg v control 11.3 mm Hg) and more sustained control of hypertension (test 323 days per patient-year with a diastolic pressure of 90 mm Hg or less v control 259 days).

Genotoxicity of the food mutagen 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ) and analogs

The food mutagen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) is an analogue of quinoline, a hepatocarcinogen. 2-Aminofluorene, benzidine and 3,2'-dimethyl-4-aminobiphenyl (DMAB) are potent inducers of unscheduled DNA repair in primary culture rat liver hepatocytes, as was IQ (151 grains/nucleus at 1 X 10(-6) M). Quinoline, on the other hand, is only weakly positive in this assay (15 grains/nucleus at 1 X 10(-3) M). IQ, quinoline and DMAB were applied topically to shaved skin of Sencar mice with promotion by 12-O-tetradecanoylphorbol 13-acetate (TPA) for 20 weeks, when 14 of 20 mice in the quinoline group had 25 tumors, but only one of 30 animals in the IQ group and five of 30 in the DMAB group were tumor-bearing. Analogs of IQ synthesized by substitution at the 2- or 3-position with amino or methyl groups were assayed with the Ames Salmonella typhimurium tester strains TA98 and TA100. Mutagenicity for TA98 is reduced in the absence of the 3-methyl group and is completely abolished with removal of the 2-amino moiety. None of these analogs are strong mutagens for TA100. Exocyclic N-oxidation is a likely obligatory step in the activation of IQ to a mutagen.

Toxicity of 6-thioguanine and 8-azaguanine to non-dividing liver cell cultures

8-azaguanine and 6-thioguanine were both toxic to non-dividing liver cells in primary cultures. In addition, these agents were toxic to an established line of liver-derived epithelial cells brought to growth arrest by serum deprivation. These observations demonstrate that the toxicity of 8-azaguanine and 6-thioguanine can occur at least in part through mechanisms that do not involve effects on DNA synthesis or incorporation of the analogs into DNA.

Serum dopamine-beta-hydroxylase activity and lateral ventricular size in affective disorders and schizophrenia

Previous studies have reported a significant negative correlation between cerebrospinal fluid DBH activity and ventricular brain ratio (VBR) in schizophrenic patients. We now report a significant negative correlation between log serum DBH activity and VBR in 28 patients with major depression (r = -0.41, p = 0.04); this correlation was also negative (r = -0.15), but not significant, in 46 schizophrenics. Eight patients (five schizophrenic, three affective disorder) with increased VBR had significantly lower serum DBH activity than the patients with normal VBR. The relationship between low CSF or serum DBH activity and increased VBR may be manifestations of the polygenetic vulnerability common to the major psychoses.

Polybrominated biphenyls are nongenotoxic and produce an epigenetic membrane effect in cultured liver cells

Polybrominated biphenyls (PBB) were studied for their genotoxic and epigenetic effects in cultured liver cells. PBB did not elicit DNA repair synthesis in rat, mouse, or hamster hepatocytes in primary cultures and did not cause mutations at the hypoxanthine-guanine phosphoribosyl transferase locus in a line of rat liver epithelial cells or in human fibroblasts cocultivated with rat hepatocytes as an activating system. In contrast, PBB inhibited intercellular molecular exchange between rat hepatocytes and liver epithelial cells indicating an epigenetic membrane effect. These data are consistent with the interpretation that PBB act as neoplasm promoters in the production of rodent liver neoplasms.

Evaluation of morpholine, 3-morpholinone, and N-substituted morpholines in the rat hepatocyte primary culture/DNA repair test

Morpholine and a series of morpholine derivatives were assayed for the potential to induce DNA repair in the rat hepatocyte primary culture/DNA repair assay. Morpholine did not induce DNA repair at dose concentrations which were not toxic (0.0001-0.1 mg/ml). Two animal metabolites of morpholine, N- methylmorpholine oxide and N- hydroxymorpholine , also did not induce DNA repair at the non-toxic concentrations tested (0.0001-10 mg/ml and 0.0001-1 mg/ml, respectively). A putative metabolite of morpholine, 3- morpholinone , was inactive (0.001-10 mg/ml) and a polyurethane foam catalyst, N- butylmorpholine (0.0001-0.1 mg/ml) was also inactive. The chemical intermediate N- hydroxyethylmorpholine induced DNA repair in the dose range 1-5 mg/ml. It was concluded that genotoxicity of substituted morpholines is a function of the substituent moiety rather than morpholine itself.

Differences in responses of 4 adult rat-liver epithelial cell lines to a spectrum of chemical mutagens

An assay for mutagenesis at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in adult rat-liver epithelial cell cultures (ARL) has been developed to take advantage of the capacity of this cell type to metabolically activate promutagens/procarcinogens. A survey of the effect of 5 types of activation-dependent mutagens/carcinogens on 4 ARL lines indicates that the ARL/HGPRT mutagenesis assay with the 4 target cell lines is able to detect a spectrum of activation-dependent carcinogens. Individual ARL lines, however, responded quite differently to a given carcinogen. The ARL/HGPRT mutagenesis assay system thus offers distinct possibilities for the study of the control of chemical biotransformation processes. However, in light of the specificity of the various cell lines to respond to a particular class of mutagens under the current assay condition, this particular assay system cannot be readily applied to routine screening of suspected environmental mutagens of unknown requirements for metabolic activation. Nevertheless, for agents with a structure related to those activated by a specific line, this system can be used to study mutagenesis resulting from intact cellular metabolism.

Serotonin uptake and imipramine binding in blood platelets and brain of Fawn-hooded and Sprague Dawley rats

The kinetic parameters of serotonin (5-HT) uptake and imipramine binding of the synaptosomes and blood platelets of male Fawn-hooded rats, which have a 5-HT storage abnormality, and normal Sprague-Dawley rats were compared. The Vmax for 5-HT uptake of synaptosomes from Fawn-hooded rats was significantly greater than that of Sprague-Dawley rats whereas that of the platelets did not differ. The Km values of both the synaptosomes and platelets of the two rat strains were not significantly different. The Bmax values for 3H-imipramine binding in both platelets and brain of Fawn-hooded rats were significantly lower than those of the Sprague-Dawley rats. The Kd of imipramine binding to platelet membranes from Fawn-hooded rats was significantly less than that of the Sprague-Dawley rats but the Kd of the synaptosomes was not significantly different. These results indicate that 5-HT uptake and imipramine binding sites may be independently regulated and that platelets do not always manifest abnormalities present in brain 5-HT neurons and vice versa.

Enhancement of benzo[a]pyrene mutagenicity by chrysotile asbestos in rat liver epithelial cells

The co-mutagenicity of chrysotile asbestos and benzo[a]pyrene (B(a)P) was studied in adult rat liver (ARL-18) epithelial cells. Exposure to chrysotile alone did not increase the mutant incidence whereas B(a)P was mutagenic. Simultaneous exposure of the cells to chrysotile and B(a)P resulted in an enhanced mutant recovery compared to exposure to either of these substances alone. However, chrysotile did not enhance the mutagenicity of the carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine.

Plasma dopamine-beta-hydroxylase in depressed patients

Plasma dopamine-beta-hydroxylase (DBH) activity was determined for 28 patients with a major affective disorder (Research Diagnostic Criteria) and 34 controls with no current, past, or family history of a psychiatric disorder. Plasma DBH activity was higher among patients (24.6 IU +/- 25.4 IU) than controls (14.5 IU +/- 8.9 IU), and subjects with plasma DBH activity greater than 25 IU were more common among patients. Unemployment and never marrying were associated with plasma DBH activity greater than 25 IU. Finally, referred patients (n = 9) had higher DBH activity (41.8 IU +/- 37.2 IU) than those responding to newspaper advertisements (n = 19, 16.5 IU +/- 11.5 IU) although these groups differed on no other variable including past history of treatment. We conclude that high plasma DBH activity may represent a vulnerability factor for depression.

A study of family physicians' telephone accessibility

To recruit physicians into a clinical trial on hypertension management, we tried to reach 162 family doctors by telephone: 68.2% of our calls were answered; 22.4% of them raised busy signals; 9.4% were not answered at all. Fewer than half of the doctors came to the phone immediately or returned our first message within a week. We called the majority several times before we finally got to speak to them. A total of 950 calls were eventually placed before we had spoken to each of 161 family doctors person-to-person-5.9 calls per doctor. One physician could not be contacted. It appears, therefore, that family physicians are very well protected against the receipt of unsolicited telephone calls-even from professional colleagues.

Epigenetic membrane effects of a possible tumor promoting type on cultured liver cells by the non-genotoxic organochlorine pesticides chlordane and heptachlor

The organochlorine pesticides chlordane and heptachlor were evaluated for their genotoxicity and epigenetic membrane effects. Both compounds were non-genotoxic in the ARLHGPRT mutagenesis assay in which the genotoxic carcinogens 7, 12-dimethylbenz[a]anthracene and benzo[a]pyrene induced significant increases in mutant incidence. The pesticides both markedly inhibited intercellular communication between cultured liver cells, a property demonstrated by many tumor promoting agents, whereas benzo[a]pyrene did not produce this epigenetic effect.

Sister-chromatid exchange induction by polycyclic aromatic hydrocarbons in an intact cell system of adult rat-liver epithelial cells

Adult rat-liver epithelial cell lines possess intrinsic metabolic capability for the biotransformation of xenobiotics and thus, are sensitive to a broad spectrum of mutagens/carcinogens in a mutagenesis assay at the hypoxanthine-guanine phosphoribosyl transferase locus. To provide another end-point of biological significance in these lines, we have investigated the application of adult rat-liver epithelial cell line 18 in a sister-chromatid exchange assay. Significant dose-dependent increases in the sister-chromatid exchange frequency occurred when liver cells were exposed to benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene. A weak but positive response was elicited by benz[a]anthracene. The present observations thus confirm the capacity of these cells to generate genotoxic metabolites from activation-dependent mutagens/carcinogens and indicate a relationship between the production of mutations and sister-chromatid exchanges by polycyclic aromatic hydrocarbons.

Inhibition of intercellular communication between liver cells by the liver tumor promoter 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane

A dose dependent inhibition of intercellular communication (metabolic cooperation) between primary cultures of rat liver hepatocytes and an established adult rat liver epithelial cell 6-thioguanine resistant strain by the liver tumor promoter 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) is demonstrated. This in vitro assay is proposed to evaluate the tumor promoting activity of oncogenic agents shown to be non-genotoxic in the liver culture systems.

Presence of anti-gamma-FA-reactive antigens in spontaneous and carcinogen-induced malignancies of experimental animals

Immunochemical analysis of various tumors, representing 12 different tissue sites of origin, revealed a gamma-fetal antigen(gamma-FA)-like component in 17 of 23 malignant neoplasms of the mouse. This antigen was identified in extracts of spontaneous and carcinogen-induced murine tumors as well as in extracts of hepatic tumors initiated in the rat with diethylnitrosamine. The occurrence of gamma-FA in 75% of the malignant tumors examined and its presence in the sera of rodents bearing transplanted and primary cancers suggests an associative relationship of potential diagnostic value. This possibility is supported by the observation that immunoprecipitable gamma-FA appeared in the sera of hepatocarcinogen-treated rats several weeks prior to the detection of alpha-fetoprotein.

The use of adult rat liver cultures in the detection of the genotoxicity of various polycyclic aromatic hydrocarbons

The hepatocyte primary culture (HPC)--DNA repair test and the adult rat liver epithelial cell (ARL)--hypoxanthine-guanine phosphoribosyl transferase (HGPRT) mutagenesis assay are two in vitro short-term tests that possess intrinsic capability for xenobiotic biotransformation. Both assays detected the genotoxicity of a variety of carcinogenic polycyclic aromatic hydrocarbons. Thus, these two tests, which embody intact cellular metabolism, are useful for the evaluation of this class of carcinogens and provide results that strengthen those obtained in tests dependent upon subcellular metabolism.

Cell cycle-specific mutagenesis at the hypoxanthine phosphoribosyltransferase locus in adult rat liver epithelial cells

The cell cycle specificity of chemical mutagenesis was studied by use of two cell synchronization techniques, one a nontoxic technique involving serum deprivation and the other a double thymidine block, to obtain rat liver epithelial cells in different phases of the cell cycle to be exposed to chemical mutagens. For both methyl methanesulfonate and N-methyl-N'-nitro-N-nitrosoguanidine, there was a cell cycle specificity of chemical mutagenesis, with the most sensitive phase being the period of DNA synthesis.

Serum dopamine-beta-hydroxylase activity in schizophrenia

On the basis of a report that serum DBH activity was significantly decreased in schizophrenics, we reexamined this relationship. Serum DBH activity was studied in 90 normal controls and 78 schizophrenics. No significant differences were found for the groups as a whole. The incidence of serum DBH activity below the median for normal controls was significantly less in chronic paranoid schizophrenics than in normal controls.

Differences between rat liver epithelial and fibroblast cells in metabolism of purines

Epithelial and fibroblast cells from adult rat liver were found to differ markedly in their metabolism of the purine hypoxanthine. Both cell types took up hypoxanthine and possessed hypoxanthine-guanine phosphoribosyl transferase for phosphoribosylating the purine. However, in the transferase assay, lysates from epithelial cells converted hypoxanthine predominantly to inosine monophosphate, with small amounts of the nucleoside inosine as product, whereas fibroblast cell lysates converted hypoxanthine predominantly to inosine. The inosine appeared not to be produced by direct ribosylation of the base, since fibroblast cell lysates had less purine nucleoside phosphorylase activity than epithelial cell lysates. Rather, the inosine produced by fibroblast lysates appeared to be derived from inosine monophosphate through catabolism of the mononucleotide by 5' nucleotidase. An inhibitor of 5' nucleotidase, thymidine triphosphate, reduced the amount of inosine formed.

Definition of conditions for the detection of genotoxic chemicals in the adult rat-liver epithelial cell/hypoxanthine-guanine phosphoribosyl transferase (ARL/HGRPT) mutagenesis assay

Conditions for the detection of genotoxic chemicals in the adult rat-liver epithelial cell/hypoxanthine-guanine phosphoribosyl transferase (ARL/HGPRT) mutagenesis assay have been defined. These included (1) a 3-day exposure to activation-dependent carcinogens; (2) a minimum of 14 days for induced mutant expression; (3) seeding density of 1 x 10(4) cells per cm2 for selection of mutants; (4) use of 6-thioguanine and (5) acceptance of genotoxicity of test chemicals if induced mutant incidence is significantly above that of the parallel run control and beyond the 98% confidence limits of the mean of the population spontaneous mutant incidence. With this protocol, the ARL/HGPRT mutagenesis assay has the capacity to activate representative members of the mycotoxin, aminoazo dye, aromatic amine and nitrosamine-types of carcinogens. This assay, offering additional metabolic parameters through intrinsic metabolic capability and providing a reliable end-point of clear biologic significance serves as a useful supplement to the Salmonella/microsome bacterial mutagenesis assay in a battery for the detection of genotoxic chemicals.

5'-Nucleotidase activities in cultured rat liver epithelial and fibroblast cells

Cell cultures of adult rat liver produced two distinct morphologic cell types: epithelial cells polygonal in shape and growing in nests of closely apposed cells, and fibroblast cells stellate in shape with little cell-cell contact at low density growth, but aligning in parallel arrays at high density. These two morphologic variants displayed dramatic differences in histochemically demonstrable 5'-nucleotidase activities. Fibroblast cells exhibited great activity throughout the cytoplasm with no concentration of activity in the cell membrane. The lesser activity in epithelial cells was concentrated on the cell membrane. The importance of this finding to the interpretation of data derived from experiments with whole liver homogenates is discussed.

Tissue distribution and biochemical properties of an interspecific tumour-associated gamma foetal antigen

A late-gestation neonatal antigen (gamma foetal antigen; gamma-FA) immunologically and biochemically unrelated to murine alpha-foetoprotein, was identified in several spontaneous and carcinogen-induced sarcomas and hepatic carcinomas of the mouse and rat. An approximate mol. wt of 35,000 for gamma-FA from both foetus and tumour was obtained by molecular-sieve chromatography and sucrose-gradient centrifugation. Radial immunodiffusion analyses of organ extracts indicated that gamma-FA could be found in several neonatal tissues, the highest concentration occurring in the spleen. In the 2-month-old mouse, only splenic tissue contained gamma-FA and at much lower levels than in the organ of the newborn mouse.

Enhancement of mutagenesis during cell replication of cultured liver epithelial cells

The susceptibility to mutagenesis of proliferating and non-proliferating mammalian cells was studied in cultured rat liver epithelial cells. Cells brought to growth quiescence by a non-toxic means were stimulated to proliferate and both types of cultures were exposed to methyl methanesulfonate (MMS). Cultures enriched in proliferating cells were more susceptible to both the toxic and mutagenic action of the mutagen than were quiescent cultures with a low level of proliferation.

Inhibition of growth of mouse ehrlich ascites by normal tissue extracts

A dialyzable component from the aqueous extracts of mouse skeletal muscle and liver inhibited in vitro growth of a mouse Ehrlich ascites. A similar component was not detected in extracts of spleen, kidney, lung, skin, serum or small intestine. The muscle component appeared to be different from that of the liver in its resistance to heat and its stability in the culture medium. Both components however were stable on storage at 4, 23 and 37 degrees C for 72 h. Intraperitoneal injection of the muscle and liver component into mice previously innoculated with Ehrlich ascites significantly decreased tumor incidence in these animals as compared with the control.