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Biomedical subjects

L M White

Publications and source records attributed to L M White.

At least 19 recordsLinked to original sources
PubMed1991

Brain acetylcholinesterase activity in forest songbirds exposed to a new method of UULV fenitrothion spraying.

Brain acetylcholinesterase (AChE) activity was measured in forest songbirds exposed to Ultra Ultra Low Volume (UULV) aerial spraying of fenitrothion in New Brunswick for spruce budworm control. Brain AChE activity was determined in 324 songbirds from the sprayed blocks and 47 from an unsprayed control area, and represented four species. In most cases, more than half of the individuals of any species sampled were diagnosed as "exposed" (greater than or equal to 20% inhibition) to the fenitrothion sprays and had a mean percent level of inhibition of 40% or greater, relative to mean control values. The proportion of birds with life-threatening levels of inhibition (greater than or equal to 50%) was usually less than 20%. The largest proportion of birds with life-threatening inhibition was found after the first 210 g AI/ha spray. The White-throated Sparrow had the highest proportion (25-55%) of individuals with life-threatening inhibition after all sprays. Brain AChE inhibition was greater in exposed birds collected after the first 210 g AI/ha spray than after the second one. Variation among species' responses to the sprays is discussed in relation to habitat and foraging preferences. Several sampling biases which may contribute to underestimation of the impact of fenitrothion spraying on birds are identified.

Acetylcholinesterase↗
PubMed1991

Acute effects of a pedicled omental graft on cold-induced brain oedema in cats.

When used as a prophylactic measure and in chronic experiments, omental transposition has been shown to reduce ischaemic and traumatic oedema in the spinal cord and ischaemic oedema in the brain. We designed this experiment to evaluate the acute effects of a pedicled omental graft on cold-induced brain oedema in cats. Focal oedema was induced in the left frontoparietal region of the brain of nine anaesthetized cats. In five cats, a laparotomy was done and a pedicled omental graft was placed on the lesioned left hemisphere immediately after the cold lesion was made. All cats were sacrificed 72 hours later, and the water content of the white matter was determined in the lesioned and the normal hemispheres. The mean water content of the lesioned hemisphere of the treated group of animals was not significantly different from that of the control group. We conclude that a pedicled omental graft failed to reduce vasogenic oedema in an acute model and probably has no role in the acute management of brain oedema.

Animals↗
PubMed1991

Effect of lead on TRH and GRF binding in rat anterior pituitary membranes.

The effect of lead on binding of the hypothalamic peptides thyroid releasing hormone (TRH) and growth hormone releasing factor (GRF) to rat anterior pituitary receptors was examined in this study. Concentrations of lead ranging from 0.01 to 1 microM did not alter [3H]TRH binding; concentrations above 1 microM increased TRH association with pituitary receptors. A previously uncharacterized ligand, [125I]GRF (human 1-44 amide), was used to examine the binding of GRF to anterior pituitary receptors. A high affinity site (GRFH = 18.1%, KH = 11.5 pM) was displaced by human growth hormone releasing factor (hGRF) (1-44)-NH2 or hGRF (1-29)-NH2 but not by rat growth hormone releasing factor (rGRF) (1-29)-NH2. Use of this ligand also revealed a class of low affinity binding sites (GRFL = 81.9%, KL = 0.39 microM) which has not been previously described. The low affinity site could be displaced by hGRF (1-44)-NH2, hGRF (1-29)-NH2 and rGRF (1-29)-NH2. A synthetic growth hormone releasing peptide (GHRP) also interacted with the low affinity GRF binding site. Lead dose-dependently displaced the binding of [125I]GRF to its pituitary receptors. The IC50 of lead for inhibiting [125I]GRF binding was 0.195 mM added lead or 52 pM free lead. These data suggest that one mechanism by which lead may affect pituitary function is through inhibition of receptor binding.

Animals↗
PubMed1991

Simultaneous immunohistochemical detection of IUdR and BrdU infused intravenously to cancer patients.

Cell cycle kinetics of solid tumors in the past have been restricted to an in vitro labeling index (LI) measurement. Two thymidine analogues, bromodeoxyuridine (BrdU) and iododeoxyuridine (IUdR), can be used to label S-phase cells in vivo because they can be detected in situ by use of monoclonal antibodies (MAb) against BrdU (Br-3) or IUdR (3D9). Patients with a variety of solid tumors (lymphoma, brain, colon cancers) received sequential intravenous IUdR and BrdU. Tumor tissue removed at the end of infusion was embedded in plastic and treated with MAb Br-3 and 3D9 sequentially, using a modification of a previously described method. Clearly single and double labeled cells were visible, which enabled us to determine the duration of S-phase (Ts) and the total cell cycle time (Tc), in addition to the LI in these tumors. Detailed control experiments using tissue culture cell lines as well as bone marrow cells from leukemic patients are described, including the comparison of this double label technique with our previously described BrdU-tritiated thymidine technique. We conclude that the two methods are comparable and that the IUdR/BrdU method permits rapid and reliable cell cycle measurements in solid tumors.

Antibodies, Monoclonal↗
PubMed1990

Vaccination with membrane-associated idiotype provides greater and more prolonged protection of animals from tumor challenge than the soluble form of idiotype.

The purpose of this work was to compare the efficacy of immunizing mice with a soluble vs a cell-associated form of a tumor Ag. A murine B cell tumor (2C3), which displays an Id on its cell surface, grows progressively and gives rise to Id-negative tumor variants in nonimmunized animals. We previously reported that the tumor variants arise as a consequence of Id-specific T cell suppression of the Id+ tumor. The Id-specific effector T cells are CD4+, CD8-. Based upon these findings vaccination protocols have been designed and tested to determine whether the expansion of tumor-specific effector T cells would eliminate the Id+ tumors and prevent the subsequent generation of Id- tumor variants in vivo. MHC-restricted T cells typically recognize soluble Ag subsequent to modification by an APC, and APC may ultimately express a processed form of the Ag that is different from that expressed on the surface of the tumor cells. Based upon this assumption, the efficacy of immunizing mice with cell-associated 2C3 Id was compared to immunization with a soluble form of the same Id. Mice were immunized with either irradiated 2C3 cells or syngeneic spleen cells to which 2C3 protein was covalently linked. These immunization protocols provided a complete and lasting protection against a tumor challenge of up to 1 x 10(6) tumor cells. In contrast, most mice hyperimmunized with a soluble form of the Id did not survive this level of tumor challenge in spite of the production of significant levels of anti-Id antibodies. Mice immunized with the soluble form of the Id, which did survive, produced slowly progressing tumors expressing a 1000-fold less of the marker Id. These results illustrate the importance of understanding and properly exploiting a host's natural response to a tumor-specific Ag when designing effective immunization protocols for cancer therapy.

Animals↗
PubMed1989

An assessment of proliferative and enzyme activity in transitional mucosa adjacent to colonic cancer.

The mucosa within 2 cm of cancers of the large bowel (transitional mucosa) shows histologic and histochemical changes which may indicate premalignant change. In this study, the authors used specimens from resected colonic tissue to compare morphometric, proliferative, and enzyme markers in transitional mucosa with those in cancer tissue and with those in uninvolved mucosa at least 10 cm from the cancer. Proliferative activity was assessed using the Ki 67 monoclonal antibody technique whereas a variety of methods were used to determine enzyme activities in mucosal homogenates. When compared to uninvolved mucosa, crypts in transitional mucosa contained greater number of cells, were significantly deeper and wider and were more likely to be branched. However, crypts in transitional mucosa had a significantly lower labelling index using the Ki 67 technique and there was no evidence of a shift in the proliferative zone towards the bowel lumen. The activities of ornithine decarboxylase, thymidine kinase, alkaline phosphatase, and lactate dehydrogenase were similar in transitional and uninvolved mucosa. Cancer tissue showed significantly higher levels of activity for ornithine decarboxylase and lactate dehydrogenase. Transitional mucosa showed morphometric changes but there were no proliferative or enzyme markers to suggest a higher than expected risk for malignant change.

Alkaline Phosphatase↗
PubMed1988

Southeast Asian folklore about pregnancy and parturition.

Southeast Asian refugees immigrating to the United States bring many traditional beliefs about pregnancy and childbearing to their new home. Harmony with nature, dualistic concepts of disease, and pathogenetic metaphor are important ingredients of indigenous health practices. Pregnant and postpartum women must be protected against "wind," lost of "heat," and poisons. Because these notions and the behaviors used to carry them out may seem bizarre to unsuspecting Western-trained health care personnel, it is important for Westerners to understand the basis for these beliefs.

Asia, Southeastern↗
PubMed1987

Characterization of ovine follicles destined to form subfunctional corpora lutea.

A study was done to test whether ovulatory follicles destined to form subfunctional corpora lutea differed from normal ovulatory follicles in steroidogenic function. Twenty-five ewes were treated with prostaglandin F2 alpha on d 11 of the estrous cycle, then unilaterally ovariectomized before (n = 13) or after (n = 12) the surge of luteinizing hormone (LH) at the induced estrus to collect "control" follicles, which would have produced normal corpora lutea. In 15 ewes, the second ovary was removed 63 to 84 h later to collect "treated" follicles before (n = 7) or after (n = 8) the second expected surge of LH. Five ewes (control) were allowed to ovulate from the remaining ovary at first estrus and another five (treated) at the second estrus (3 to 4 d later). Treated ewes had lower serum progesterone than control ewes during the ensuing cycle (P less than .05). Treated follicles contained less estradiol in the theca (4.4 +/- .6 vs 10.0 +/- 2.5 ng; P less than .05), less androstenedione (.1 +/- .1 vs 1.0 +/- .2 ng) and estradiol (.5 +/- .1 vs 2.9 +/- 2.2 ng) in the granulosa (P less than .05) and less progesterone in the follicular fluid (.8 +/- .4 vs 3.3 +/- .8 ng; P less than .05) than control follicles, when removed before the surge of LH. Follicles removed after the surge of LH did not differ. In conclusion, ovulatory follicles with low steroidogenic function became corpora lutea that secreted lower-than-normal quantities of progesterone.

Androstenedione↗
PubMed1984

Sex ratio after insemination of bovine spermatozoa isolated using a bovine serum albumin gradient.

This experiment was undertaken to determine if a method reported to successfully enrich the proportion of Y-chromosome-bearing spermatozoa in human semen could be adapted for separation of bovine spermatozoa. Semen was collected from four Angus bulls and aliquots were either separated on discontinuous gradients of bovine serum albumin (BSA) or untreated before processing for cryopreservation. Two hundred seventy-one cows or heifers were assigned randomly to be artificially inseminated (20 X 10(6) sperm/insemination) with separated or unseparated spermatozoa. The proportions of male offspring were 45 and 54% after inseminations with separated or unseparated spermatozoa, respectively. In a second phase of the experiment, pooled semen from three Holstein bulls was either extended and frozen without separation or frozen after separation using the discontinuous BSA gradient. Separated and unseparated spermatozoa were analyzed by flow cytometry to determine the ratio of X- and Y-chromosome-bearing spermatozoa based on differences in DNA content. The ratios of X- and Y-bearing spermatozoa in separated or unseparated samples were indistinguishable. We concluded that the separation method did not enrich the proportion of Y-bearing bovine spermatozoa.

Animals↗
PubMed1984

Characteristics of bovine spermatozoa after migration through a bovine serum albumin gradient.

Experiments were conducted to determine the efficiency with which viable, morphologically normal bovine spermatozoa could be isolated using a discontinuous bovine serum albumin (BSA) gradient. In the first experiment, extended semen was layered on top of a BSA gradient (4% BSA over 10% BSA) contained in a 500-ml separatory funnel. When comparing 1, 3, 5, 7, 14 or 21 X 10(9) spermatozoa applied to the gradient, the percentage of spermatozoa recovered from the lower third of the 10% BSA ranged from 2.9 to 18.5%. The greatest recovery was achieved when 1 X 10(9) sperm cells were applied. Increasing the number of spermatozoa applied to the gradient increased the percentage of spermatozoa remaining in the upper portions of the gradient. Motility of spermatozoa immediately after collection from the 10% BSA layer of the gradient was greater than 90%, regardless of the number of spermatozoa applied. In a second experiment with freeze-thawed separated or unseparated spermatozoa, post-thaw motility (greater than 60%) and acrosomal integrity (greater than 85%) of separated spermatozoa (4 or 10% BSA layer) was greater (P less than .05) than that of unseparated spermatozoa (38 and 66%, respectively). The discontinuous gradient excluded decapitated spermatozoa and spermatozoa with mid-piece and principal piece abnormalities from entering the lower layers. Sperm cells with head abnormalities were not separated. These data indicate that a population of spermatozoa with a high frequency of viable, motile, morphologically-normal bovine spermatozoa can be isolated using a discontinuous BSA gradient.

Animals↗