Differential release of LH and FSH in cyclic mares in response to synthetic Gn-RH

Mares at different stages of the oestrous cycle were given a single intravenous injection of 0.5 mg synthetic Gn-RH. The mean area of the induced LH peak was significantly less at mid-cycle (Day 10-11) than at any other time. The mean height of the LH peak above preinjection concentration was greater at late oestrus and early cycle (Day 5-6) than at mid-cycle and early oestrus. There were no significant different in mean FSH responses. The LH:FSH ratio for both height and area of induced peaks was significantly less at mid-cycle than at other times of injection. These results suggest that one releasing hormone could cause the release of both FSH and LH in the normal cyclic mare.

ICRF-159 enhancement of radiation response in combined modality therapies. II. Differential responses of tumour and normal tissues

The combined effect of the chemotherapeutic agent ICRF-159 and radiation on the proliferative status of tumor/normal systems has been evaluated using the Lewis lung tumour in BDF1 mice. We have previously shown that a 25 mg/kg dose of ICRF-159, given at 3h intervals X4 before irradiation, significantly enhanced tumour growth retardation relative to a single dose of 100 mg/kg before irradiation. Whilst both single and fractionated drug treatments produced a transient inhibition of cell proliferation, comparisons of the temporal recovery from the antiproliferative effect of radiation in both tumour and intestinal epithelium suggested that single acute doses of ICRF-159 fail to potentiate the radiation response of either tissue. Protracted drug administration before irradiation, however, markedly decreases the post-radiation proliferative recovery of the tumour, without significantly altering intestinal recovery. The data suggest that both drug concentration and/or exposure time determine the interactions seen with combined modes.

ICRF-159 enhancement of radiation response in combined modality therapies. I. Time/dose relationships for tumour response

The combined effect of the chemotherapeutic agent ICRF-159 and irradiation were evaluated using the Lewis lung tumour (LL). At a daily dose of 25 mg/kg, ICOF given alone prevented the progressive growth of LL. Daily pretreatment also potentiated the effects of radiation (600 rad) on tumour growth, provided the pretreatment kinetics of the tumour permitted a response to radiation alone. Single acute doses of the drug failed to alter the growth of LL, and when combined with radiation failed to enhance the radiation effect. Fractionation of the drug (25 mg/kg; 4 doses at 3h intervals) before irradiation, however, results in immediate effects on tumour growth which are more than additive. The results suggest that a low dose of ICRF-159 for extended periods is more effective in enhancing radiotherapy than a high dose provided acutely.

Antibiotic prophylaxis in total hip replacement

A controlled prospective trial to compare the efficacy of the antibiotics cephaloridine and flucloxacillin in preventing infection after total hip replacement was conducted at three hospitals. The antibiotic regimens began before surgery, cephaloridine being continued for 12 hours and flucloxacillin for 14 days afterwards. Over an 18-month period 297 patients undergoing a total of 310 hip replacements were entered into the trial and randomly allocated to one of the regimens. The follow-up period ranged from one to two and a half years. All operations were performed in conventional operating theatres; at two of the hospitals these were also used by various other surgical disciplines. Four patients developed deep infection, two having received the cephaloridine and two the flucloxacillin regimen. The overall rate of deep infection was therefore 1.3%. Thus three doses of cephaloridine proved to be as effective as a two-week regimen of flucloxacillin. Giving a prophylactic systemic antibiotic reduced the incidence of infection to a level comparable with that obtained in ultra-clean-air operating enclosures.

Quantitation of damage to the alveolar epithelium by means of type 2 cell proliferation

The purpose of this study was to determine whether the amount of alveolar epithelial tissue damaged during exposure of NO2 could be quantified by measuring the proliferative response to Type 2 cells. To accomplishe this, we used tissues from previously published experiments in which rats had been exposed to NO2 and the proliferative response to Type 2 cells had been measured during a 5-day period. The proportion of alveolar epithelium damaged was determined by stereologic examination with electron microscopy of tissue sections from those rats exposed to NO2 for 24 hours. These values were then compared with the total proliferative response to Type 2 cells for the 5 days of exposure. The study demonstrated that increasing tissue damage is assocaited with a greater proliferative response to Type 2 cells. The high degree of correlation (r = 0.93) indicates that the proliferative response of Type 2 cells can be used as an indirect means to quantify acute damage to the alveolar epithelium.

Effect of 2',3'-dideoxythymidine-5'-triphosphate on HeLa cell in vitro DNA synthesis: evidence that DNA polymerase alpha is the only polymerase required for cellular DNA replication

We have studied the effects of the nucleotide analogue, 2',3'-dideoxythymidine-5'-triphosphate (ddTTP) on replicative DNA synthesis in HeLa cell lysates. As previously demonstrated (1), such lysates carry out extensive DNA synthesis in vitro, at rates and in a fashion similar to in vivo DNA replication. We report here that all aspects of DNA synthesis in such lysates (total dNTP incorporation, elongation of continuous nascent strands, and the initiation, elongation, and joining of Okazaki pieces) are only slightly inhibited by concentrations of ddTTP as high as 100-500 micrometer when the dTTP concentration is maintained at 10 micrometer. This finding is consistent with the report by Edenberg, Anderson, and DePamphilis (2) that all aspects of replicative in vitro simian virus 40 DNA synthesis are also resistant to ddTTP. We also find, in agreement with Edenberg, Anderson, and DePamphilis (2), that DNA synthesis catalyzed by DNA polymerases beta or gamma is easily inhibited by ddTTP, while synthesis catalyzed by DNA polymerase alpha is very resistant. These observations suggest that DNA polymerase alpha may be the only DNA polymerase required for all aspects of cellular DNA synthesis.

Participation of cultured teratocarcinoma cells in mouse embryogenesis

Mouse blastocysts were microsurgically injected with embryonal carcinoma cells from in vitro teratocarcinoma cell lines C17, C86, SIKR-OSB, and PCC3/A/I. The embryos were allowed to develop to term and the resulting offspring were analysed for chimaerism using coat colour markers and isozyme differences of the enzyme glucose phosphate isomerase. When injected into blastocysts, cell line C86 produced tumours in six of 74 animals born. The tumours were detected at birth and were poorly differentiated neuroectodermal teratocarcinomas. Cell line C17 gave 13 chimaeras in 77 mice born, five of which showed chimaerism only in normal tissues, mainly melanocytes of the coat and eye. The other eight chimaeras developed tumours. Seven of these developed in adult animals and were mainly fibrosarcomas. Cell line SIKR-OSB resulted in one normal chimaera in 44 mice born. Of 86 animals born following injection of cell line PCC3/A/1, there was one chimaera with a small tumour and three normal chimaeras. The levels of chimaerism were generally very low. The mice were test bred but with no evidence of germ line chimaerism. The karyotypes of all the cell lines were abnormal. How this and other factors such as cell cycle times might affect the incorporation of embryonal cells into the developing embryo is discussed.

Biochemical markers of the progress of differentiation in cloned teratocarcinoma cell lines

The progeny of single teratocarcinoma cells will give rise to several different cell types in vitro, and the latter were shown to be functionally differentiated by biochemical criteria. In all these studies, cloned lines of mouse teratocarcinoma cells were assayed during the course of differentiation for some biochemical products characteristic of the tissues formed. The carcinoembryonic protein, alpha-foetoprotein, was not synthesized by undifferentiated embryonal carcinoma (EC) cells, but was synthesized in increasing amounts during their differentiation to endoderm-type cells in suspension culture. alpha-Foetoprotein was shown to be a product of endoderm cells, but not all endoderm cells synthesized this protein. During the course of further differentiation when EC cells or aggregates were grown in tissue-culture dishes, other biochemical products appeared. In cultures containing predominantly nerve-type cells, there was a 30-fold increase in the specific activity of acetylcholinesterase, with concomitant appearance of the aldolase isoenzyme characteristic of mouse brain. In some cultures, a small amount of muscle-type cell formation was marked by the appearance of the MB isoenzyme of creatine phosphokinase. Generally, biochemical differentiation was immature.

Properties of the H-4-II-E tumor cell system. II. In vitro characteristics of an experimental tumor cell line

The growth and cell proliferation characteristics of the H-4-II-E cell line, giving rise to hepatoma H-4-II-E when inoculated into male ACI rats, were studied in vitro. Following seedling of 2 x 10(5) cells into culture dishes, exponential cell growth occurs in cultures fed both at 24 hr and 48 hr intervals with a population doubling time of 18-4 hr. Plateau phase growth conditions are established on day 7 and day 5 for cultures fed at 24 hr and 48 hr intervals respectively. Both the plateau phase cell density and the maintenance of plateau phase appear dependent on the frequency of feeding. For cultures fed daily, the transition from exponetial growth to plateau phase results from both a reduction in the number of proliferating cells (99% v. 35%) as well as an elongation of the cell cycle (17-7 hr v. 128-4 hr). The cell proliferation characteristics of the culture are further discussed in reference to both cell growth and feeding schedules of other cell lines.

Properties of the H-4-II-E tumor cell system. I. Growth and cell proliferation kinetics of an experimental hepatoma

Growth and cell proliferation kinetics of hepatoma H-4-II-E and its tissue culture derivative have been studied to establish the characteristics of an in vivo--in vitro solid tumor model. The H-4-II-E line, originating from the Reuber H-35 hepatoma, can be maintained and studied either in cell culture or as a transplantable solid tumor in ACI male rats. In addition it allows for the in vitro assay of cell survival following treatment of animal tumors in situ. In vivo, hepatoma H-4-II-E is rapidly growing tumor with a mean doubling time of 49-2 hr. The cell cyle time is 39-1 hr with a cell loss factor of 0-32. Retrospective examination of tumor specimens obtained during the establishment of the H-4-II-E tumor system demonstrates that both structural as well as cell population changes have occurred. The biological characteristics of the primary tumor (H-35) and an early intermediate stage (H-35tc2) are compared with H-4-II-E and the histopathological, growth and cell kinetic changes are discussed.

Renewal of the terminal bronchiolar epithelium in the rat following exposure to NO2 or O3

Rats were exposed to either NO2 or O3 to determine whether nonciliated cells (Clara cells) could divide and differentiate into ciliated cells in the terminal bronchioles. Dividing cells were labeled with tritiated thymidine, visualized in the light and electron microscopes using autoradiographic techniques, and studied for up to 15 days after labeling. Electron microscopic autoradiography 1 hour after injection of tritiated thymidine showed that all labeled cells in the terminal bronchioles were nonciliated. However, 4 days after injection of tritiated thymidine, 67.8 per cent of the labeled cells were nonciliated and 32.2 per cent were ciliated. Light microscopic autoradiography showed that the new labeled ciliated cell population was stable for up to 15 days. These results indicate that nonciliated cells divide and the sister cells may form new ciliated and nonciliated cells. Thus, nonciliated cells can act as progenitor cells for the terminal bronchiolar epithelium.

Changes in cellularity induced by radiation in a solid tumour

The growth, and cellular responses of Morris hepatoma 3924 A to a locally-administered dose of 3750 R X-rays were studied using the following parameters; (1) relative tumour volume changes; (2) tritiated thymidine (3H-TdR) incorporation into DNA; (3) tumour DNA content and (4) cellular analysis, including 3H-TdR labelling index, mitotic index, aberrant mitotic frequency and relative cell density. Before depression of tumour growth, cell proliferation is temporarily interuppted. As proliferation is reinitiated, a short-lived synhcrony and prolongation of cell-cycle traverse are reflected in (a) the labelling index and mitotic index, (b) the relative cell density, and (c) the rate of incorporation of 3H-TdR into DNA. Within 4 days after radiation, cell proliferation and 3H-TdR incorporation are significantly depressed. Simultaneously there are reductions in both the relative cell density and tumour DNA contents, and these remain depressed as the tumours initiate regression. From these studies, it is apparent that the cellular responses to radiation insult occur well in advance of measurable volume changes and are observed both in tumours that continue to regress and in those that initiate regrowth.

Effects of 100% oxygen on cell division in lung alveoli of squirrel monkeys

The purpose of this study was to determine the effects of 100% oxygen on cell division in lung alveoli of squirrel monkeys. To accomplish this, squirrel monkeys were exposed to 100% oxygen for up to 5 d. Prior to sacrifice, cells preparing to divide were labeled with tritiated thymidine (3H-Tdr). Labeled cells were visualized with autoradiographic techniques, counted with the light microscope, and expressed in terms of a labeling index. In the present study it was shown that DNA synthesis was initially inhibited by exposure to 100% oxygen. However, within 3 d it was returning to normal and by 5 d was well above control levels. Analysis of the cell types involved showed that the large increase in labeling was due to an increase in dividing Type 2 cells, which is thought to be for replacement of damaged Type 1 cells.

Postnatal changes in total and free thyroxine and triiodothyronine in foal serum

Total tyhroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3) and free triiodothyronine (FT3) concentrations in foal umbilical cord blood were respectively 14, 5 7 and 3 times the concentrations of these hormones in adult horse blood. The TT4 levels in foals declined rapidly to reach adult concentrations by Day 16 and FT4 levels declined steadily during the first 3 months of life. Foal TT3 levels rose during the first 10 hr after birth and thereafter declined, although they were still X2-5 higher than adult levels at 3 months of age. Levels of FT3 similarly increased after birth becoming X8 higher than adult levels at 3 days of age. They declined after this time but were still twice the normal adult levels at 3 months of age. Associated with these age changes were an increase in the free hormone percentage and a decrease in binding protein concentration. The very high levels of thyroid hormones in newborn foals may be responsible for their extremely high thermogenic capacity and rapid pre- and post-natal rates of growth, especially of the musculo-skeletal and nervous systems.

Serum concentrations of FSH, LH and progesterone during the oestrous cycle and early pregnancy in the mare

Heterologous radioimmunoassays were developed for equine FSH and LH. Serum concentrations were measured in twenty-three mares throughout the oestrous cycle and early pregnancy. FSH concentrations were raised fivefold by 'surges' rather than 'spiked', occurring at 10- to 11-day intervals during the oestrous cycle and early pregnancy. The late oestrous/early dioestrous surge of FSH appeared to initiate development of up to twenty follicles. The mid-dioestrous surge may be important for the further development of follicles destined to ovulate 10 to 13 days later. Levels of LH were increasing by the onset of oestrus and reached their maximum 1 to 2 days after ovulation. This rise in LH may stimuate maturation of the follicle throughout oestrus. An inverse relationship between progesterone and LH levels occurred, suggesting a negative feedback, but there was no such relationship between FSH and progesterone concentrations.

Effects of 60 and 80% oxygen on cell division in lung alveoli of squirrel monkeys

The purpose of this study was to determine the effects on cell division of 60 and 80% oxygen in the lung alveoli of squirrel monkeys. To accomplish this, squirrel monkeys were exposed to 60 and 80% oxygen for up to 8 d. Prior to sacrifice, cells preparing to divide were labeled with tritiated thymidine (3H-TdR). Labeled cells were visualized with autoradiographic techinques, counted with the light microscope, and expressed in terms of a labeling index. In the present study, it was shown that DNA synthesis was not changed by exposure to 60%; however, with exposure to 80% oxygen, cell labeling was well above control levels by 5 d. Analysis of the cell types involved showed an increase in labeling. due to an increase in dividing Type 2 cells. Other cells in the alveolar wall also showed an increase in labeling

A light and electron microscopical study of the nervous tissue of mouse teratomas

Teratomas are tumours which may arise spontaneously in the testis or ovary or may be induced experimentally by the implantation of young embryos into ectopic sites. In this study the nervous tissue within mouse teratomas was investigated by light and electronmicroscopy. Characteristic neuroepithelial tubules, neurons, glia and neuropil were recognized and showed no ultrastructural abnormality apart from collagenous infiltration. Synapses were frequently observed. However, other features of mature C.N.S. tissue including myelin and complex synaptic configurations were never seen, and it was not possible to recognize distinct classes of neurons, or organizations of cells and processes which characterized specific regions of the C.N.S. The limited differentiation of the nervous tissue of teratomas is discussed with reference to the normal development of C.N.A. in vivo and in vitro. The presence of synapses in the nervous tissue of teratomas is interpreted as a reflection of an intrinsic tendency of neuronal processes to form these specialized contacts even under conditions which prevent the development of certain other characteristics of nervous tissue.

Susceptibility of thymectomized and irradiated mice to challenge with several organisms and the effect of dapsone on infection with Mycobacterium leprae

B6C3F1 mice that had been thymectomized at 8 to 12 weeks of age, subjected to 950 R of whole-body X irradiation, and transfused with syngeneic bone marrow were challenged in a footpad with Mycobacterium leprae or M. marinum, or intravenously or intraperitioneally with Listeria monocytogenes. Also, mice inoculated with M. leprae in a hind footpad were administered dapsone in the mouse chow. The thymectomized-irradiated (T + R) mice did not survive as well as non-thymectomized mice when housed in the vivarium with no special precautions, but survived sufficiently well to permit the completion of some long-term experiments. M. leprae multiplied to a higher "ceiling" and survived longer in the T + R mice than in the non-thymectomized controls. But a ceiling to multiplication of M. leprae was imposed, and finally the organisms were killed. The histopathological appearance of the footpad tissues, studied by electron microscopy, was consistent with the measurements of bacterial numbers and viability. Swelling of the footpad after local inoculation with M. marinum was greater in T + R mice than in non-thymectomized controls. Similarly, the number of L. monocytogenes following intravenous challenge was greater in the spleens of T + R than of non-thymectomized mice, and the survival of the T + R mice was impaired after intraperitoneal challenge with L.monocytogenes, compared to the survival of non-thymectomized mice. None of these differences was striking, suggesting that these T + R mice had retained or regained some immune competence. The effects of dapsone treatment of T + R mice inoculated with M. leprae were much the same as those of treatment of non-thymectomized mice. Because these T + R mice were not greatly immunosuppressed, they would not have provided a model of human lepromatous leprosy suitable for chemotherapeutic studies.

Differentiation of clonal lines of teratocarcinoma cells: formation of embryoid bodies in vitro

The differentiation in vitro of clonal pluripotent teratocarcinoma cells is reported. The first stage of this process is the formation of simple embryoid bodies which are identical to those found in animals bearing intraperitoneal teratocarcinomas. They consist of an inner core of embryonal carcinoma cells surrounded by a layer of endodermal cells which produce Reichert's membrane. The endodermal cells become apparent shortly after the embryonal carcinoma cells have formed aggregates which are loosely attached to the substratum. One clonal teratocarcinoma line was found to produce complex cystic embryoid bodies in vitro. Following formation of the endodermal cells, extensive differentiation to a wide variety of cell types occurs. There are similarities between the process of embryoid body formation and the early events of differentiation of the mouse embryo.

Auditory versus visual processing of three sets of simultaneous digit pairs

Two experiments were conducted to determine whether the auditory and visual systems process simultaneously presented pairs of alphanumeric information differently. In Experiment 1, different groups of subjects were given extensive practice recalling pairs of superimposed visual or auditory digits in simultaneous order (the order of arrival) or successive order (one member of each digit pair in turn, followed by the other pair member). For auditory input, successive order of recall was more accurate, particularly for the last two of three pairs presented, whereas for visual input, simultaneous order of recall was more accurate. In Experiment 2, subjects were cued to recall in one or the other order either immediately before or after stimulus input. Recall order results were the same as for Experiment 1, and precuing did not facilitate recall in either order for both modalities. These results suggest that processing in the auditory system can only occur successively across time, whereas as in the visual system processing can only occur simultaneously in space.

Early response of lung to low levels of ozone

The epithelial response in the terminal bronchioles and alveoli was examined after exposure to approximately 0.5 and 0.9 ppm ozone (O(3)). Loss of ciliated cells from the terminal bronchiole was pronounced after 6 to 10 hours of exposure; however, nonciliated cells were resistant to injury from O(3). In contrast, type 1 alveolar lining cells were very sensitive to O(2) and were severely damaged or removed from significant areas of the proximal alveoli after as little as 2 hours of exposure to 0.5 ppm. The basement lamina was left devoid of an epithelium with the exception of type 2 cells, which were very resistant and retained a relatively normal appearance. Under continuous exposure, repair of the lesion area was accomplished in approximately 48 hours through proliferation of the type 2 cells. The new cells were cuboidal at first but subsequently became more squamous in appearance. Exposure for 8 to 10 hours followed by residence in clean air resulted in a proliferative response at 48 hours, about equal to that observed after continuous exposure.

Renewal of alveolar epithelium in the rat following exposure to NO2

This research was undertaken to study the kinetics of Type 2 cell division and the fate of the Type 2 sister cell following exposure to NO(2). To accomplish this, male rats were exposed to NO(2). Dividing cells were labeled with (3)H-TdR and studied with autoradiographic technics in the light and electron microscopes for up to 72 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. The fate of the Type 2 sister cells was determined by studying tissues at 24, 48 and 72 hours after labeling with (3)H-TdR. The results show that Type 2 cells may divide and the sister cells transform into Type 1 cells. These data support an interpretation of the mechanism for cell renewal of the alveolar epithelium in which Type 2 cells are the progenitor cells for Type 1 cells.

Cell division of alveolar macrophages in rat lung following exposure to NO2

The purpose of this research was to study cell division of alveolar macrophages following exposure of rats to NO(2). Dividing cells were labeled with (3)H-TdR and studied for 12 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. Dividing alveolar macrophages were localized in alveoli near the openings of terminal bronchioles. There were no morphologic differences observed between labeled and unlabeled macrophages. Estimates of the durations of the various phases of the cell cycle gave approximate values of: G(2), 1 hour; t(2), 1.8 hour; M, 2.8 hours; and S, 5.8 hours. This evidence, combined with that of others, is compatible with an interpretation for alveolar cell renewal in which marrow-derived cells enter the alveoli and become macrophages. While in the alveoli, the cells may divide and thus increase their numbers. Eventually the macrophages are extruded from the alveoli. Alveolar macrophages were classified as a dividing, transient renewing cell population.