A Comparative Analysis of State Regulations for Use of Agricultural Chemicals

Policies to regulate pesticides at the national level have not changed as new issues, such as groundwater contamination, have emerged. Therefore, various states are responding. This paper discusses recent state initiatives in regulating pesticides to prevent groundwater contamination, and suggests trends in these policies. A survey of legislators who have sponsored pesticide/groundwater contamination legislation is presented. Survey results show the factors affecting bill introduction, the influence of interest groups on the bills, important issues in bill debate, and trends in future legislation. A statistical analysis of the survey states and survey responses is also presented, using economic, political, and physical factors as explanatory variables

Health Orientation, Beliefs, and Use of Health Services Among Minority, High-risk Expectant Mothers

This article reports on initial findings of a continuing longitudinal study investigating the relationships of health beliefs as conceptualized by the health belief model and the use of well-baby services among first-time black mothers. The health beliefs of mothers about their babies were measured before the babies were born and during their use of the services at the baby's first and sixth-month visits. Mothers in the sample who became nonusers of the well-baby services were also interviewed. This report describes the results of the first interview of the 662 females who composed the sample for the study, including the following characteristics of a minority, high-risk population: health orientation, health beliefs about their unborn babies, and use of health services. These findings are discussed with implications for community health nursing practice with maternal clients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73774/1/j.1525-1446.1988.tb00553.x.pd

The interaction of steroids with the hypothalamic-pituitary-testicular system in the adult male rat

Major functions of the mature male gonad are the production of gametes and steroid hormones. Extratesticular as well as intratesticular factors regulate these two male gonadal functions which are associated with two distinct cell compartments in the testis. It has been known for a long time that hypophysectomy is followed by gonadal atrophy and arrest of the spermatogenic process which only will proceed to a primary spermatocyte stage. The anterior pituitary gland appears to play an essential role in the regulation of the testis and systematic studies on the relationship between brain structures and the male gonad started in the late nineteen twenties and early thirties. The finding that testicular functions were controlled by the hypophysis stimulated almost simultaneously experiments on the reverse issue, i.e. whether testicular products can affect the hypophysis (Moore and Price, 1930). The connections between these systems are the anterior pituitary gonadotrophiC hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It is now well established that the major control of pituitary function resides in the hypothalamus, although other brain structures also are involved in the regulation of the pituitary gland (Szent.3.gothai et al. 1968; Mess and Martini, 1968; Halasz, 1969). Hypothalamic gonadotrophin releasing factor (GnRF) , reaching the anterior pituitary gland via a portal system, stimulates syn-thesis (Redding et al. 1972) and release (Schally et al. 1968) of the hypophyseal gonadotrophins LH and FSH in special gonadotroph cells. The many mutually dependent and complicated interactions between hypothalamus, hypophysis and testis at different functional levels are intriguing and make their study very attractive

Control of the release of some hypophysial portal vessel peptides

The aim of this thesis was to investigate hypothalamic-pituitary control by measuring the release of neuropeptides into pituitary stalk blood. The neuropeptides measured were luteinizing hormone-releasing hormone (LHRH) and the 'gut peptides' cholecystokinin (CCK), gastrin and vasoactive intestinal polypeptide (VIP). Studies in castrated rats showed that, (1) despite marked increases in pituitary gonadotro_phin secretion and the number of LHRH receptors in the anterior pituitary gland, the amount of LHRH in stalk blood was similar to that in control rats; (2) the release of LHRH into stalk blood induced by electrical stimulation of the median eminence (ME) was significantly lower than in control rats; (3) administration of oestradiol, 5a-dihydrotestosterone or testosterone (T), suppressed the post-castration rise in plasma luteinizing hormone (LH) but had no effect on LHRH released into stalk blood or the increased number of LHRH receptors in the anterior pituitary gland. Experiments using intact and castrated rats made hyperprolactinaemic by implanting two anterior pituitary glands under the kidney capsule showed that, (1) the suppression of gonadotrophin release in intact and castrated hyperprolactinaemic rats was not accompanied by a decrease in LHRH release into stalk blood; (2) electrical stimulation of the ME was as effective in hyperprolactinaemic rats as in control rats in increasing LHRH release into stalk blood; (3) implantation of T capsules into castrated hyperprolactinaemic rats suppressed gonadotrophin but not LHRH secretion. Catechol oestrogens stimulated the release of LH in pre-pubertal male and female rats but suppressed LH release induced by pregnant mare serum gonadotrophin. CCK and VIP, but not gastrin, were released in significantly higher concentrations into stalk blood than into peripheral blood of adult male rats. Electrical stimulation of several areas of the brain known to contain CCK, gastrin or VIP did not alter the release of these peptides. Removal of the major peripheral source of CCK and gastrin (the gastric antrum) or VIP (the entire gut), significantly lowered CCK and gastrin concentrations but did not reduce VIP release into stalk blood. VIP release into stalk blood at various times of the oestrous cycle under Althesin, Ketalar, Sagatal or urethane anaesthesia showed no clear-cut changes. Therefore, it is unlikely that CCK and gastrin are physiological hypothalamic-pituitary regulatory factors. The physiological significance of the higher amounts of VIP in stalk blood compared with peripheral blood remains to be determined

Ovarian function in the gilt and lactating sow

Maturational changes during the follicular phase of the porcine oestrous cycle were investigated in spontaneously cycling gilts. The results revealed considerable variation in the morphological and biochemical development of dominant follicles in the early follicular phase. This asynchrony was emphasised by the marked differences in follicular fluid steroid concentrations and LH binding to granulose cells and theca tissue between follicles of identical size within the same ovary. The nature of this variation may have great significance on our present understanding of asynchronies in embryo development. On the basis of the variables assessed in this study, those follicles destined to ovulate or to become atretic were only readily distinguishable on Day 20 of the oestrous cycle, suggesting that the selection of the preovulatory population continues over a 4 day period from about Day 16 to Day 20 of the cycle and, furthermore, that the selection process involves some initial maturation even in those unselected follicles that ultimately join the atretic pool. Leading on from this study, the control of the initiation of follicular development in lactating primiparous sows was examined by assessing the relationships between ovarian activity and circulating hormone levels following manipulation of the suckling stimulus. In the first experiment, piglet suckling behaviour and follicular development were 'investigated following a reduction in litter size to five piglets (split-weaning), seven days before weaning at 21 days post-partum. Overall, morphological and biochemical follicular development were significantly advanced (p < 0.001) in the treatment sows. The significantly (p < 0.001) greater concentration of follicular fluid oestradiol in follicles recovered from the split-weaned sows suggested that the supply of androgen substrate was probably limiting production of this steroid in the control animals. It was proposed that the latter was due to inadequate gonadotrophin stimulation. The comparative ethological study revealed that the remaining split-weaned piglets 'multiple-suckled' quarters vacated by their heavier litter mates. Despite a constant suckling frequency, suckling intensity was reduced in the split-weaned litters as evidenced by a regression in mammary tissue growth in the dams. In a subsequent experiment, further manipulation of the suckling stimulus was achieved by physically restricting the number of mammary quarters available to the piglets. Canvas sheeting strapped around the anterior quarters of one group of sows (cover) limited the five piglets remaining after split-weaning to suckle only the posterior quarters. An investigation of circulating hormone levels, 12 hours before and 48 hours after the start of treatment, revealed that, compared to the split-weaned and control sows, LH levels were significantly (p < 0.001) elevated in the cover sows with a concomitant significant (p < 0.001) depression in circulating prolactin. Although split-weaning induced a similar endocrine response in several sows, this effect was short-lived and overall, levels of both hormones were similar in the split-weaned group to those recorded in the control sows. The concentration of oxytocin, released at suckling was unaffected by litter size or the intensity of mammary stimulation. Ovarian activity at weaning was significantly enhanced in the cover (p < 0.001) and split-weaned (p < 0.001) groups. Hence, it was concluded that the critical factor influencing hormone levels and follicular development in the lactating sow was the neural intensity of the suckling stimulus. The cumulative data of the lactation experiments suggest that in practice, serious consideration should be given to the use of litter size reduction as a means of effectively improving the performance of the primiparous sow and her litter during lactation

Ovarian function in the gilt and lactating sow

Maturational changes during the follicular phase of the porcine oestrous cycle were investigated in spontaneously cycling gilts. The results revealed considerable variation in the morphological and biochemical development of dominant follicles in the early follicular phase. This asynchrony was emphasised by the marked differences in follicular fluid steroid concentrations and LH binding to granulose cells and theca tissue between follicles of identical size within the same ovary. The nature of this variation may have great significance on our present understanding of asynchronies in embryo development. On the basis of the variables assessed in this study, those follicles destined to ovulate or to become atretic were only readily distinguishable on Day 20 of the oestrous cycle, suggesting that the selection of the preovulatory population continues over a 4 day period from about Day 16 to Day 20 of the cycle and, furthermore, that the selection process involves some initial maturation even in those unselected follicles that ultimately join the atretic pool. Leading on from this study, the control of the initiation of follicular development in lactating primiparous sows was examined by assessing the relationships between ovarian activity and circulating hormone levels following manipulation of the suckling stimulus. In the first experiment, piglet suckling behaviour and follicular development were 'investigated following a reduction in litter size to five piglets (split-weaning), seven days before weaning at 21 days post-partum. Overall, morphological and biochemical follicular development were significantly advanced (p < 0.001) in the treatment sows. The significantly (p < 0.001) greater concentration of follicular fluid oestradiol in follicles recovered from the split-weaned sows suggested that the supply of androgen substrate was probably limiting production of this steroid in the control animals. It was proposed that the latter was due to inadequate gonadotrophin stimulation. The comparative ethological study revealed that the remaining split-weaned piglets 'multiple-suckled' quarters vacated by their heavier litter mates. Despite a constant suckling frequency, suckling intensity was reduced in the split-weaned litters as evidenced by a regression in mammary tissue growth in the dams. In a subsequent experiment, further manipulation of the suckling stimulus was achieved by physically restricting the number of mammary quarters available to the piglets. Canvas sheeting strapped around the anterior quarters of one group of sows (cover) limited the five piglets remaining after split-weaning to suckle only the posterior quarters. An investigation of circulating hormone levels, 12 hours before and 48 hours after the start of treatment, revealed that, compared to the split-weaned and control sows, LH levels were significantly (p < 0.001) elevated in the cover sows with a concomitant significant (p < 0.001) depression in circulating prolactin. Although split-weaning induced a similar endocrine response in several sows, this effect was short-lived and overall, levels of both hormones were similar in the split-weaned group to those recorded in the control sows. The concentration of oxytocin, released at suckling was unaffected by litter size or the intensity of mammary stimulation. Ovarian activity at weaning was significantly enhanced in the cover (p < 0.001) and split-weaned (p < 0.001) groups. Hence, it was concluded that the critical factor influencing hormone levels and follicular development in the lactating sow was the neural intensity of the suckling stimulus. The cumulative data of the lactation experiments suggest that in practice, serious consideration should be given to the use of litter size reduction as a means of effectively improving the performance of the primiparous sow and her litter during lactation