Biomedical subjects

A J Hackett

Publications and source records attributed to A J Hackett.

At least 37 records · Page 2Linked to original sources

PubMed1985

Reproductive performance of Finnish Landrace and Suffolk sheep maintained indoors year-round.

The reproductive performance (fertility and prolificacy) of Finnish Landrace (Finn) and Suffolk sheep on an accelerated breeding program was evaluated. Both breeds were contained in each of two separate flocks housed indoors year-round on expanded metal floors in windowless buildings. The two flocks were bred alternately at 4-mo intervals in January, May and September. The sheep were exposed to either an abrupt (ALR) or constant (CLR) lighting regimen. Data from nine breedings during a 4-yr period were considered. Fertility was significantly higher for ewes in the ALR lighting regimen. Fertility was lower for ewes bred in September. For ewes that had lambed from breeding 8 mo earlier, fertility was higher for Finn ewes than for Suffolk ewes; however, similar fertility levels were observed in both breeds if the ewes had not lambed following the previous breeding. Higher prolificacy was observed in the Finn ewes than in the Suffolk ewes, but the differences in prolificacy varied with the month of breeding. The probability of a ewe having more than one lamb was significantly higher for Finn ewes than for Suffolk ewes in both January and May breedings, but was similar in September breedings. Incorporating the Finnish Landrace breed into an accelerated breeding program for sheep maintained indoors year-round is a practical way to increase the number of lambs born. Controlling daylength and dividing the flock into smaller flocks are also practical procedures to increase lamb production.

Animals↗

PubMed1985

Response to doxorubicin of cultured normal and cancerous human mammary epithelial cells.

Epithelial cells were isolated and cultured from a number of human mammary specimens of both cancerous and noncancerous origin. Doxorubicin (Dx) sensitivity was measured at second passage with the use of a highly efficient clonogenic assay. For 23 different tumor specimens derived from patients without previous chemotherapy, the drug concentrations required to kill 50% of the cells varied approximately 35-fold. In contrast, for 11 tumor specimens from patients who relapsed after regimens containing Dx, the drug concentration for 50% survival varied only fivefold and the dose-response curves for these specimens clustered at the more resistant end of the spectrum. A wide range of sensitivities was also observed among 13 noncancerous mammary specimens; however, tumor tissue and noncancerous tissue from the same donor were similar. When cultures were subjected to drug incubation periods of 1 and 4 hours, dose-response curves were superimposable when plotted as a function of drug concentration multiplied by time.

Breast↗

PubMed1985

The incidence of cystic ovaries in dairy cattle housed in a total confinement system.

The incidence of cystic ovaries following 1830 calvings of 1061 dairy cows maintained in total confinement was evaluated. The overall incidence was 14% of lactations and 22% of cows during a three year period. Fewer primiparous than multiparous cows became cystic, 5.7% vs 18%, respectively. There was an unexplained higher incidence (18%) among calvings in 1979 than in 1980 (12%) and 1981 (13%). There were no effects due to season of calving or genetic line of cow. During the last year of the study milk production by cystic cows was significantly greater than that by non-cystic cows.

Animals↗

PubMed1984

The biology of breast cancer at the cellular level.

Two properties seem fundamental to cancer; heterogeneity and progression (Foulds (1975) Academic Press, New York; Heppner et al. (1979) Commentaries on Research in Breast Disease, Vol. 1 (Bulbrook, R. and Taylor, D.J., eds.), pp. 177-191, Plenum Press, New York). Relatively little is understood about the premalignant stages of human breast disease in vivo. When the disease manifests as invasive carcinoma, its behavior exhibits great diversity, sometimes metastasizing rapidly, while in other cases 10-30 years pass before metastases proliferate. Here we review various aspects of breast cancer in vivo and consider how they predict properties of breast cancer found in culture. All of the experiments are consistent with the hypothesis proposed by Nowell (1976) Science 194, 23-28, that a fundamental aspect of malignancy is an increased genetic instability and that many of the cells within tumors are nonviable results of genetic instability. We suggest that most of the viable cells within primary breast carcinomas are diploid and are not yet capable of aspects of metastatic spread. What these cells have attained is an increased propensity for genetic instability which enables them to generate randomly aneuploid but frequently lethal genetic configurations. Occasionally one of these altered genomes is associated with the ability to proliferate at a metastatic site. This hypothesis implies that metastases from various patients may have arisen by divergent pathways and may also be divergent in many other aspects of their physiology, unrelated to malignancy. Such extreme heterogeneity may hamper attempts to understand fundamental aspects of malignancy. Hence we suggest that the less anaplastic and less divergent diploid cells within the primary carcinomas might be an important resource to gain insights into the critical alterations that are responsible for initiating frankly malignant behavior.

Animals↗

PubMed1984

Fertility of ewe lambs maintained indoors year-round on an accelerated breeding program.

Data from records of 330 crossbred ewe lambs mated to 142 rams over 11 breeding periods were analyzed for lambing percentage to one service. These ewe lambs in two separate flocks were reared and maintained indoors year-round and were derived from the three synthetic crossbred strains being developed at the Animal Research Centre in Ottawa, Ontario, Canada. At first exposure to rams, the ewes were 6 to 7 mo of age and had no hormonal treatments to induce or synchronize estrus. The two flocks were bred alternately in January, May or September to establish an 8 mo breeding cycle. The rams were at least 10 mo old and were maintained in one of two lighting regimens. Fifteen percent of the ewes lambed and the average prolificacy was 1.6. It appears that ewe lambs mated to rams maintained in a constant day length (10 h light: 14 h dark/24 h) environment had lower fertility than those ewe lambs mated to rams maintained in an environment such that the day length was altered between 4 mo of 10 h light: 14 h dark/24 h and 4 mo of 18 h light: 6 h dark/24 h. Although the fertility level was low, the data suggest that the breeding of ewes 6 to 7 mo of age is feasible.

Animal Husbandry↗

PubMed1984

Onset of estrus in dairy cows maintained indoors year-round.

During 6 mo two active testosterone-treated females fitted with chin-ball markers and paint were used to ascertain the time of onset of estrus in 56 cows of three genetic lines and at various stages of lactation. The two treated females were rotated every 24 h, and two colors of paint were used, one color for night, 1800 to 0600 h, and the other for day, 0600 to 1800 h. The incidence of behavioral signs of estrus, standing, mounting activity, and mucus discharge, also was recorded. More cows (65%) came into estrus during the night, and only 78% of the total marked cows, assumed to be in estrus, were observed standing by the herdsman, indicating that 22% of the cows would not have been observed in estrus by early morning and late afternoon observation by the herdsman. Similarly, of the marked cows a mucus discharge was observed for 60% and mounting activity by 62%. Neither parity nor days postpartum affected either time of onset of estrus or other overt signs of estrus. Differences among the genetic lines for standing and mounting activity were unexplained.

Animal Husbandry↗

PubMed1984

Estrus detection and subsequent reproduction in dairy cows continuously housed indoors.

Records (1554) from 961 cows continuously housed indoors in two types of barns were analyzed for occurrence and detection of estrus and subsequent reproduction. Variables, percentage of cows observed in estrus by 55 days postpartum, days to first recorded estrus and first service, conception rates, service intervals, days open, and services per conception were analyzed by least squares procedures for year of calving, month of calving, genetic line, barn-type-parity subclasses, and interaction of month by line. A higher percentage of multiparous cows in the tie-stall barn (60%) were observed in estrus by 55 days postpartum than those in the loose-housing barn (50%). Days to first recorded estrus and to first service, 54 and 81, were less for tie-stall cows than for loose-housing cows, 66 and 91. Conception rates at first service and overall conception, 54 and 91%, were higher for tie-stall cows than for loose-housing cows, 42 and 80%. A higher percentage of primiparous cows (69%) was in estrus by 55 days than multiparous cows (55%). Days to first estrus and first service were less for primiparous cows, 47 and 70, than multiparous cows, 60 and 80. Days open were less for primiparous cows. Primiparous cows required 1.9 services per conception compared with 1.7 for multiparous cows.

Animals↗

PubMed1982

Effect of PMSG on the reproductive performance of totally confined ewes bred at synchronized estrus.

The reproductive performance (fertility, prolificacy and fecundity of totally confined sheep in a controlled breeding program at the Animal Research Centre (ARC) was analyzed to evaluate the effect of pregnant mares' serum gonadotrophin (PMSG) on ewes synchronized for estrus with fluorogestone acetate (FGA). PMSG did not significantly enhance reproductive performance. Fertility for ewes receiving 500 IU PMSG was 57% and for ewes not receiving PMSG it was 47%. Corresponding values for prolificacy were 2.4 and 2.2, and for fecundity, 144 and 103%. The reproductive performance was not affected by any of the other factors (flock, strain, lighting regime, ram age or reproductive status of the ewe) indigenous to the controlled breeding program for sheep housed in total confinement.

Journal Article↗

PubMed1982

Reproductive performance of totally confined sheep bred with semen extended in a lactose-egg yolk-glycerol buffer and stored at 5 degrees C.

Two experiments were carried out in January and May 1975 to study reproductive performance (fertility, prolificacy and fecundity) of totally confined sheep synchronized for estrus. The main objective of the first experiment was to compare reproductive performance of ewes bred naturally to those bred by artificial insemination. Semen for artificial insemination was collected by either artificial vagina or electroejaculation and stored for up to 36 hours at 5 degrees C. A second objective was to evaluate the effect of pregnant mares' serum gonadotrophin on the reproductive performance of ewes synchronized for estrus. Fertility was 53% for ewes bred by natural mating, 34% for ewes receiving pregnant mares' serum gonadotrophin and bred by artificial insemination, and 9% for those not receiving pregnant mares' serum gonadotrophin and bred by artificial insemination. There was no difference in fertility between ewes bred with semen collected by artificial vagina or by electroejaculation. A similar pattern was observed for fecundity. Average prolificacy was 2.0 with no significant differences among mating methods or pregnant mares' serum gonadotrophin application being observed. In the second experiment, the reproductive performance of ewes inseminated with semen stores at 5 degrees C for 48 to 60 hours was compared to that of ewes inseminated with semen stores for 24 to 36 hours. No significant differences in the reproductive performance were detected. Although average fertility (9%) and fecundity (19%) were low, prolificacy averaged 2.0 lambs per ewe lambing.

Animals↗

PubMed1982

Effectiveness of photoperiod stimulation on reproductive performance of sheep housed continuously indoors on an accelerated breeding schedule.

Over five breeding periods, the reproductive performance (fertility, prolificacy and fecundity) of three strains of sheep housed continuously indoors was measured. The sheep were maintained as two separate flocks, A and B, with similar genetic background on an eight month accelerated breeding schedule under one of three lighting regimes, abrupt, contracted or constant, to induce ovarian activity. Overall fertility to one estrus was 59%. For flock A, fertility was greatest under the contracted lighting regime and lowest under the constant lighting regime; the opposite was true for flock B. Among the three strains, fertility was lowest for the Dam 2 strain in flock A. Prolificacy averaged 1.8 lambs per ewe lambing and was similar under each of the three lighting regimes. Fecundity (averaging 106%), the number of lambs born per 100 ewes exposed to rams, generally followed the pattern of fertility.

Animals↗

PubMed1982

Plasma levels of copper, iron and zinc during the estrous cycle of the ewe.

Serum levels of copper, iron and zinc were determined throughout complete estrous cycles in 16 ewes. All ewes were normally cycling females exhibiting normal serum progesterone patterns. Copper serum levels tended to be higher during the preovulatory and ovulatory times, presumably due to the transfer of hepatic celuloplasmin as a result of the release of endogenous estrogen. Iron and zinc plasma levels were higher during estrous when the ovarian tissue requirement was higher. It is suggested that the control mechanism responsible for the variations in copper, iron and zinc plasma levels during the estrous cycle may be hormonal in nature.

Animals↗

PubMed1981

Use of an efficient method for culturing human mammary epithelial cells to study adriamycin sensitivity.

Techniques are described for isolating, cryopreserving, and culturing human mammary epithelial cells of both normal and malignant origin. The cells can be grown either in mass culture or as a clonal assay suitable for quantitating drug sensitivity. With this clonal assay plating efficiencies of 6%-41% were routinely obtained. We examined the response to adriamycin of five different primary carcinoma cultures from patients without prior drug therapy. We were able to detect heterogeneity in response to adriamycin among the breast carcinoma cultures as well as heterogeneity among subpopulations within a single carcinoma. The differences in adriamycin sensitivity were unrelated to growth rates in culture.

Adult↗

PubMed1981

Effects of prostaglandin F2 alpha and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance of fluorogestone acetate PMSG-treated ewes.

Two experiments were conducted to examine the effect of prostaglandin F2 alpha (PGF2 alpha) and pregnant mares' serum gonadotropin (PMSG) on the reproductive performance (fertility, prolificacy and fecundity) of ewes previously treated with fluorogestone acetate (FGA) and PMSG. In the first experiment, 29 ewes were synchronized for estrus with FGA and PMSG but not bred at the postsynchronization estrus. On day 10 of the first post-synchronization estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to experienced, fertile, raddled rams. Twenty-four of the 29 ewes (83%) had viable fetuses 9 weeks after the PGF2 alpha-PMSG treatment. In the second experiment, 64 ewes were treated with FGA-PMSG, and 33 were exposed to fertile, raddled rams at the synchronized estrus. A second group of 31 ewes was not bred at the synchronized estrus, but on day 12 of the postsynchronized estrous cycle, they were injected IM with 15 mg PGF2 alpha and 500 IU PMSG and exposed to fertile, raddled rams. Sixty-six percent of the 33 ewes lambed in the FGA-PMSG-treated group and 60% of the 31 ewes lambed in the PGF2 alpha-PMSG-treated group. Differences in reproductive performance between these two treatment groups were not statistically significant. The results suggest that the PGF2 alpha-PMSG treatment combination does not adversely affect reproductive performance of ewes.

Animals↗

PubMed1981

Clonal proliferation of cultured nonmalignant and malignant human breast epithelia.

We have developed a method for clonal growth of human mammary epithelial cells of both nonmalignant and malignant origin. Plating efficiencies of 1 to 50% were obtained by seeding second-passage mammary epithelial cells on fibroblast feeder layers in an enriched medium composed of various hormones and growth factors, as well as conditioned media from three specific human cell lines. Single mammary epithelial cells seeded sparsely onto the fibroblasts underwent at least eight population doublings to form large, readily visible colonies. Optimal colony formation required both feeder cells and the enriched medium. Epithelial colonies containing at least 16 cells were visible 5 days postseeding, and these colonies continued to grow progressively. Plating efficiency and colony size were similar on ultraviolet-irradiated or nonirradiated fibroblasts. The number of colonies formed was proportional to the number of epithelial cells plated. The colonies were identified as epithelial by the presence of human mammary epithelial antigens.

Adult↗

PubMed1981

Reproduction in three genetic lines of dairy cattle housed a total confinement system.

Dairy cattle of three genetic lines maintained year round in total confinement (either in loose housing or tie stall barn) were monitored for estrous cycle activity and reproductive performance. Only 54% of the 492 cows calving over a 12 month interval were observed in estrus at least once between parturition and day 55 postpartum. There was a significant genetic line by barn interaction in the detection of estrus mainly because more cows of the Ayrshire line were observed in estrus in the tie stall barn (75%) compared to cows of the same line in the loose housing barn (48%). Month of calving had no effect on the subsequent detection of estrus. Conceptions to either first, second, third or fourth and greater services were 43, 44, 43 and 37%, respectively. Cows housed in the loose housing barn had significantly more days open than cows in the tie stall barn. Season of calving had no effect on the subsequent reproductive performance. Failure to detect estrus was the major problem for not obtaining a 12 month calving interval.

Animals↗

PubMed1980

Growth of normal human mammary cells in culture.

Reduction mammoplasty tissue was used to obtain short-term cultures of human epithelial cell populations. Digestion of tissue with collagenase and hyaluronidase resulted in cell clusters (organoids) resembling ductal and alveolar structures; these could be separated by filtration from the stromal components. Epithelial outgrowth from these organoids was greatly enhanced by the addition of conditioned medium from other human epithelial and myoepithelial cell lines. Additionally, the mammary epithelial growth was stimulated by insulin, hydrocortisone, epidermal growth factor, and steroid hormones. With this enriched nutritional environment, active cell division could be maintained for 1 to 3 months and cells could be serially subcultured 1 to 4 times.

Breast↗

PubMed1980

Effect of dose and time of injection of prostaglandin F(2alpha) in cycling ewes.

A study was done to evaluate the efficacy of graded doses of prostaglandin F(2alpha) (PGF(2alpha)) to induce regression of the corpus luteum and hence estrus, in cycling ewes when given on various days of the estrous cycle. One hundred cycling cross-bred ewes were observed twice daily (08:00 and 20:00 h) for marking by raddled vasectomized rams. After estrus was confirmed in marked ewes by assay of plasma progesterone concentration, the ewes were treated in pairs with 0, 5, 10, 15 or 20 mg PGF(2alpha) on day 2, 3, 4, 7, 8, 9, 12, 13, 14 or 15 of an estrous cycle and then exposed to a raddled ram of known libido and fertility. Plasma progesterone levels were determined on the day of, and on the day following PGF(2alpha)-treatment to monitor luteal function. Ewes marked between one and five days after treatment and having a decrease in plasma progesterone were considered to have responded to the treatment. The percentages of ewes responding were 10, 35, 60, 70 and 95 to doses of 0, 5, 10, 15 and 20 mg PGF(2alpha) respectively. Differences due to dose were significant (P < 0.01) with the two higher doses being more effective. There were differences due to the day of injection, with treatments on days 2 and 3 being less effective.

Journal Article↗

PubMed1980

Influence of estradiol-17 beta on fertility in confined sheep inseminated with frozen semen.

Impaired sperm transport is believed to be a major cause of reduced fertiity in ewes inseminated with frozen semen. Because of suggestions that estradiol improves sperm transport, estradiol-17 beta was given to mature ewes at progestagen-induced estrus to test effects on fertility after artificial insemination with frozen semen. Conception rates, based on progesterone determinations made 18 days after insemination, were 43% for ewes injected with 50 microgram estradiol-17 beta and inseminated with frozen semsn, 52% for ewes inseminated with frozen semen but given no estradiol and 86% for ewes inseminated with fresh semen. Lambing rates were 6, 35 and 69%, respectively. The markedly greater difference between conception rates and lambing rates for the estradiol-treated ewes suggests that estradiol caused a substantial increase in the early embryonic mortality associated with the use of frozen semen.

Animals↗