Effects of delivery rate and non-contingent infusion of cocaine on cocaine self-administration in rhesus monkeys.

The goal of this study was to determine whether slowly infused, response-independent cocaine would reduce cocaine self-administration in an animal model of drug abuse. Seven male rhesus monkeys self-administered i.v. cocaine on a fixed-ratio 30 schedule (5-min time-out). With unit dose (0.056 mg/kg per infusion for one monkey and 0.032 mg/kg per infusion for the rest) and infusion volume (0.5 ml) held constant, the rate of delivery was manipulated (0.125, 0.1875, 0.375, 0.75 and 3 ml/min, with infusions lasting 240, 160, 80, 40, and 10 s, respectively). Response rates increased monotonically as a function of delivery rate. Responding for cocaine at the slowest delivery rate did not differ from saline. The effects of infusing additional cocaine (starting 30 min prior to the session) at this non-reinforcing rate (0.125 ml/min) were then determined. Delivery rate of the self-administered infusion was manipulated as before. Non-contingent cocaine significantly increased responding for cocaine (at the fastest delivery rate) and for saline. While non-contingent cocaine reduced responding for cocaine in two of the seven monkeys, it also significantly reduced responding in three monkeys that responded for food on the same schedule. Plasma levels of cocaine delivered at rates of 0.125 and 3 ml/min were compared in five other monkeys. While a higher peak was reached with the faster infusion, levels did not differ after 5 min. Thus, when an infusion became available (after the 5-min time-out) in the self-administration experiments, plasma levels should not have differed regardless of the delivery rate. These results suggest that a low-dose, slow-delivery treatment with cocaine might prime or reinstate drug seeking rather than decrease it.

Selective use of indocyanine green angiography for occult choroidal neovascularization.

PURPOSE: Indocyanine green angiography is useful in situations where fluorescein angiography shows occult choroidal neovascularization or pigment epithelial detachment. We sought to determine how often the selective application of indocyanine green angiography results in useful information for eyes with occult choroidal neovascularization. METHODS: We reviewed 153 consecutive indocyanine green angiograms and identified 77 in which corresponding fluorescein angiograms showed occult choroidal neovascularization or pigment epithelial detachment. We examined the indocyanine green angiograms to detect areas of hyperfluorescence and to classify the margins of hyperfluorescence as well demarcated or poorly demarcated. RESULTS: Of 77 eyes, 42 (55%) eyes had occult choroidal neovascularization by fluorescein angiography, seven (9%) eyes had both classic and occult choroidal neovascularization by fluorescein angiography, and 28 (36%) eyes had pigment epithelial detachments. Of 42 eyes with occult choroidal neovascularization by fluorescein angiography, 21 (50%) had well-demarcated margins, 13 (31%) had poorly demarcated margins, and eight (19%) had no detectable hyperfluorescence by indocyanine green angiography. Of seven eyes with both classic and occult choroidal neovascularization by fluorescein angiography, two had both poorly demarcated and well-demarcated borders, two had only poorly demarcated borders, and three had well-demarcated borders by indocyanine green. The indocyanine green angiogram showed 23 (82%) of 28 pigment epithelial detachments to have well-demarcated borders of hyperfluorescence; 13 (57%) of 23 were treated. CONCLUSION: Indocyanine green angiography adds clinically useful information to fluorescein angiography by demonstrating well-demarcated areas of hyperfluorescence in 50% of eyes selected because of diagnosis of occult choroidal neovascularization and in 82% of eyes selected because of pigment epithelial detachment.

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories: study design.

The most commonly used genotoxicity assays for cultured mammalian cells are mammalian cell mutagenesis, chromosome aberrations/SCE, hepatocyte UDS, and cell transformation. Since their inception, protocols for these assays have been modified in various laboratories. It has been observed that minor but potentially significant method modifications frequently remain unpublished (Swierenga et al., 1983) but should be considered in the development of recommended protocols. The present study was undertaken to determine the current 'state of the art' for these tests. Detailed questionnaires on culture conditions and testing protocols for both stock and test cell populations were designed with the assistance of an international advisory committee and sent to all research and contract laboratories that could be readily identified in Canada, U.S.A. and Europe. Responses from 425 completed questionnaires were analyzed to determine the most commonly used approach and modifications for each procedural step. As expected, the results show a large degree of interlaboratory variation. Detailed protocols for conducting each assay have been prepared and include: stepwise instructions, precautionary measures and practical solutions to common problems associated with each assay; recipes for media and solutions; formulas for quantifying genotoxic responses; reference lists of related assays; guidelines for interpretation; and discussions of the applications, advantages and disadvantages of each test.

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories: II. Mutation in Chinese hamster ovary, V79 Chinese hamster lung and L5178Y mouse lymphoma cells.

Laboratory protocols and guidelines have been developed for the performance of point mutation assays using Chinese hamster ovary (CHO) cells, V79 cells, and L5178Y mouse lymphoma cells. Since only minor differences in the treatment of CHO and V79 cells exist, these two assays could be combined in one procedural guideline. A second protocol was developed for the mouse lymphoma assay in order to incorporate concerns and methods specific to that cell type and genetic locus. The protocols were based primarily on current laboratory practices as determined by responses to a detailed questionnaire completed by North-American and European governmental, university and contract laboratories involved with in vitro mutation testing. This report identifies those modifications to previously described methodologies which are being used on a regular basis, provides recommendations, and also serves to clarify confusing or inconsistent practices.

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories: I. Unscheduled DNA synthesis assay in rat hepatocyte cultures.

A protocol based primarily on current laboratory practices in the performance of the unscheduled DNA synthesis (UDS) assay with primary rat hepatocyte cultures has been developed. These guidelines were developed using tabulated responses to a detailed questionnaire completed by North American and European governmental, university and contract laboratories involved with the UDS test. This report identifies those modifications to previously described methodologies which are used on a regular basis and also serves to clarify confusing or inconsistent practices. Although this protocol pertains specifically to the use of primary rat hepatocyte cultures, it can be modified to incorporate other types of cells in which certain aspects remain the same.

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories: III. Cell transformation in C3H/10T1/2 mouse embryo cell, BALB/c 3T3 mouse fibroblast and Syrian hamster embryo cell cultures.

A standardized protocol and guidelines for the performance of cell transformation testing in mouse embryo (C3H/10T1/2), mouse fibroblast (BALB/c 3T3) and Syrian hamster embryo (SHE) cells have been developed. The protocol is based primarily on current laboratory practices as determined by responses to a detailed questionnaire completed by North American and European governmental, university and contract laboratories involved with cell transformation experimentation. This report identifies those modifications to previously described methodologies which are being used on a regular basis and also serves to clarify confusing or inconsistent practices.

Recommended protocols based on a survey of current practice in genotoxicity testing laboratories, IV. Chromosome aberration and sister-chromatid exchange in Chinese hamster ovary, V79 Chinese hamster lung and human lymphocyte cultures.

A recommended protocol has been developed for chromosomal aberration and sister-chromatid exchange assays in CHO, V79 and human lymphocyte cultures. The protocol was based on the responses to a detailed questionnaire completed by North-American and European governmental, university, and contract laboratories using these tests. This report identifies those modifications to previously described methods that are used on a regular basis and clarifies confusing or inconsistent practices. These protocols can be modified for use in other types of cells.

Bovine leukosis. IV. Trypanosomiasis, lymphocytosis and DNA synthesis.

The possible influence of natural trypanosome infection on lymphocytosis and DNA synthesizing lymphocyte counts in peripheral blood was determined on 220 cows from two leukosis herds and 25 cows from leukosis free control herd. Trypanosome incidences were determined during summers of 1969 and 1970 by inoculating whole blood onto blood agar slants and incubating at room temperature. Incidence of trypanosomiasis in cattle was found to be variable, possibly due to factors affecting the primary isolation of Trypanosoma theileri. A small trypanosome resembling Trypanosoma uniforme was found occasionally as a concomitant infection with T. theileri. Trypanosomiasis occurred with equal frequency in the animals of the leukosis and the control herds. No correlations were noted between trypanosomiasis, lymphocytosis and DNA synthesizing lymphocytes in peripheral circulation.

Bovine leukosis. I. Seasonal influences on lymphocytosis.

The influence of seasons on lymphocytosis status of 321 mature cows from two leukosis herds and a leukosis free control herd was investigated. Animals were bled at three to four month intervals and classifed according to the Göttingen leukosis key as lymphocytosis negative, suspect or positive. The percentage distribution of different hematological classes of animals fluctuated greatly between bleedings, however "persistent lymphocytosis" in animals of leukosis herds was noted to be a constant feature and was not influenced by seasonal variations. The study indicates that 1) multiple samplings are necessary for differentiating between transient and persistent lymphocytosis; 2) caution should be exercised in pooling data from different leukosis herds as these may not be samples from a single leukosis population.

Bovine leukosis. II. Comparison of hematological classification with DNA synthesis between herds.

Blood samples of 126 mature cows with "persistent" hematological status from two leukosis herds and a leukosis free control herd were collected for determining hematological status and estimation of replicating lymphocytes. To quantitate the number of DNA synthesizing cells, the blood was incubated with tritiated thymidine in vitro followed by autoradiography. Classification of animals according to lymphocytosis status did not reveal clearly whether or not a difference existed between the two leukosis herds. The estimation of DNA synthesizing lymphocyte counts showed that the animals from the two leukosis herds did not differ from each other while differing significantly from control herd animals. The study suggests that the similarities between the two leukosis herds, while ambiguous on lymphocyte counts alone, become clear when DNA synthesizing cell counts are compared. Thus the animals of the two leukosis herds belonged to the same "leukosis" population.

Bovine leukosis III. Relationship between lymphocytosis and DNA synthetic lymphocytes.

The relationship between lymphocytosis and cell counts of lymophocytes synthesizing DNA in peripheral blood of 321 mature cows from two leukosis herds and a control herd and 11 cows with leukotic tumors was investigated. Only data from 20 control herd and 109 leukosis herd animals which remained persistently in either negative or suspect or positive hematological class on repeated bleedings were utilized. In the leukotic cattle these studies were limited to the terminal stages of the disease.A positive correlation was noted between the number of DNA synthesizing lymphocytes and lymphocytosis. Corresponding increases in peripheral blood lymphocytes and in the numbers of DNA synthesizing lymphocytes of leukotic cattle and animals of leukosis herds was attributed to impaired lymphocytopoiesis. The evaluation of the control herd and of the leukosis herds was not clear-cut on the basis of lymphocyte counts alone, although the differences were more clearly defined when the data from hematological studies and estimation of DNA synthesizing lymphocytes were evaluated. The Göttingen bovine leukosis key classification in conjunction with the estimation of DNA synthesizing cells was found to be a reliable procedure for the early recognition of the leukosis herds but not leukotic individuals.

Cancer risk from inorganics.

Inorganic metals and minerals for which there is evidence of carcinogenicity are identified. The risk of cancer from contact with them in the work place, the general environment, and under conditions of clinical (medical) exposure is discussed. The evidence indicates that minerals and metals most often influence cancer development through their action as cocarcinogens. The relationship between the physical form of mineral fibers, smoking and carcinogenic risk is emphasized. Metals are categorized as established (As, Be, Cr, Ni), suspected (Cd, Pb) and possible carcinogens (Table 6), based on the existing in vitro, animal experimental and human epidemiological data. Cancer risk and possible modes of action of elements in each class are discussed. Views on mechanisms that may be responsible for the carcinogenicity of metals are updated and analysed. Some specific examples of cancer risks associated with the clinical use of potentially carcinogenic metals and from radioactive pharmaceuticals used in therapy and diagnosis are presented. Questions are raised as to the effectiveness of conventional dosimetry in accurately measuring risk from radiopharmaceuticals.

An equine intersex with unilateral gonadal agenesis.

Cytogenetic and histological studies have been carried out on an intersex horse which was clinically diagnosed as a cryptorchid. The horse had the general conformation of a stallion but the external genitalia included a well developed vulva and a penis. The right testis which was descended was devoid of germ cells and the left "gonad" located in the cavum vaginale contained neither testicular nor ovarian tissue. The male duct system on both sides were relatively well developed despite the absence of a testis on the left side. Chromosome analysis on cultured cells from the descended testis revealed the presence of four chromosomally-distinct cell types with XX, XY, XXY and XO sex complements indicating a quadruple mosaicism. The presence of polymorphonuclear neutrophils exhibiting a drumstick, in the hemopoietic tissues and a sex chromatin body in the nucleated cells of buccal mucosa suggest that mosaicism prevails in other somatic tissues of the horse. On the basis of information derived from similar conditions in humans and some domestic animals it would appear that this horse resulted from an XXY zygote. The four cell types noted in the horse probably resulted through mitotic mechanisms favouring the loss of an X and a Y at different stages during embryonic development. The absence of gonad on the left side of this horse might be causally related to the preponderance of XO cell types in the somatic blastema during early gonadal differentiation.

Growth and cytogenetic characteristics of nickel sulphide-induced rhabdomyosarcomas in rats.

Rhabdomyosarcomas induced by single intramuscular injections of nickel sulphide (Ni3S2) in Fischer and Hooded rats were cultured in vivo and in vitro to study their growth characteristics and chromosomal constitution. The tumor cell suspensions cultured in vitro exhibited more myogenic differentiation on the coverslips than those cells grown in vivo in diffusion chambers. A characteristic feature of in vivo cultures was the appearance of microclusters which resembled the primary tumors. Chromosome analyses of primary tumors revealed that a majority of these had a modal number in the diploid or near diploid range. Fischer rat primary tumor cells exhibited abnormal configurations including rings, dicentrics and triradials. A comparison of the chromosome make-up of the primary tumors and their metastases was performed on four sets of tumors. Three out of four metastases examined showed the diploid chromosome make-up characteristic of the primary tumors suggesting that the tumors with the diploid or near diploid chromosome constitution are more likely to produce metastases.

Nickel sulphide-induced rhabdomyosarcomata in rats.

Fifty-nine Fischer rat tumors and eleven Hooded rat tumors induced by intramuscular injection of Ni3S2 were examined and their histopathologic and cytologic characteristics studied. Nine out of eleven Hooded rat tumors metastasized whereas 15 out of 59 Fischer rat tumors metastasized within 30 days. Histopathological characterization of the Ni3S2-induced tumors was made according to their preponderant cellular constitution. They were grouped into six types: well-differentiated rhabdomyosarcomas, poorly-differentiated rhabdomyosarcomas, embryonal rhabdomyosarcomas, mesenchymal tumors, leiomyosarcoma-like tumors and fibrosarcoma-like tumors. Forty-seven of total of 70 were rhabdomyosarcomas. Tumors with shorter latent periods in Fischer rats and tumors with fleshy and soft texture demonstrated a higher incidence of metastases.