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Biomedical subjects

D L Meyer

Publications and source records attributed to D L Meyer.

At least 19 recordsLinked to original sources
PubMed2007

Serum hormone concentrations relative to carcass composition of a random allotment of commercial-fed beef cattle.

Cattle (n = 995 steers and 757 heifers) were randomly selected from a commercial abattoir (Emporia, KS) to determine the relationships between USDA quality and yield grade characteristics and serum concentrations of leptin, IGF-I, and GH. Animals were randomly selected postexsanguination on the slaughter line on 4 occasions (March, May, August, and January). Blood was collected at exsanguination and transported to the University of Missouri for analysis. Sex and hide color were recorded. Carcass data included HCW, 12th-rib fat thickness, KPH, LM area, and marbling score, which were collected from each carcass approximately 24 h postmortem. Average serum leptin concentrations were greater (P = 0.008) for heifers (11.9 ng/mL) than steers (10.9 ng/mL). Heifers had lighter carcasses (331.9 vs. 352.2 kg, P < 0.001), greater 12th-rib fat measurements (1.3 vs. 1.1 cm, P < 0.001), greater KPH (2.5 vs. 2.4%, P < 0.001), and more marbling (Small(40) vs. Small(10), P < 0.001) than steers. Positive correlations (P < 0.01) existed between leptin concentration and marbling score (r = 0.28), 12th-rib fat depth (r = 0.37), KPH (r = 0.23), and USDA yield grade (r = 0.32). Negative correlations were found between leptin and IGF-I (r = -0.11; P < 0.001) and leptin and GH (r = -0.32; P < 0.001). Negative correlations (P < 0.01) were observed for IGF-I and KPH (r = -0.23) and marbling score (r = -0.20), whereas GH was most highly negatively correlated with KPH (r = -0.23; P < 0.001). Leptin concentration accounted for variation (P < 0.001) in a model separating least squares means across USDA quality grade, separating USDA standard (8.5 ng/mL), select (10.3 ng/mL), low choice (12.2 ng/mL), and upper 2/3 choice/prime (>12.9 ng/mL) carcasses. There was no difference (P = 0.31) observed in leptin concentrations between the upper 2/3 choice and prime carcasses (12.9 and 14.2 ng/mL, respectively). Relationships within endocrine profiles and between endocrine concentrations and carcass quality characteristics may prove to be a useful tool for the prediction of beef carcass composition.

Abattoirs↗
PubMed2005

Growth rate, body composition, and meat tenderness in early vs. traditionally weaned beef calves.

One hundred forty spring-born Angus x Gelbvieh and purebred Angus steers were selected for study as early weaned (EW; average age at weaning = 90 +/- 30 d) or traditionally weaned (TW; average age at weaning = 174 +/- 37 d) steers that were non-implanted or implanted (Synovex-S, Fort Dodge Animal Health, Overland Park, KS). Initially, steers were sorted by age, sire, and farm, and then allotted randomly in a 2 x 2 factorial arrangement of treatments of EW implanted (EWI), EW nonimplanted (EWN), TW implanted (TWI), or TW nonimplanted (TWN). Ultrasound measurements (US) of LM area (LMA), 12th rib fat thickness (US-BF), and marbling (US-M) were collected every 28 d during the time that steers were on feed. At 202 d of age, EW calves had larger US-LMA, US-BF, and BW than TW calves (37.9 vs. 32.3 cm2, 0.38 vs. 0.26 cm, and 271.6 vs. 218.9 kg, respectively; P < 0.001). At slaughter, EW calves had heavier HCW (290.4 vs. 279.7 kg, respectively; P < 0.05) and greater USDA marbling scores (51.25 vs. 46.26, respectively; P < 0.05) than TW calves; more EW steers graded USDA Choice or greater (P = 0.05). However, no differences were detected in BW (P = 0.15), LMA (P = 0.39), BF (P = 0.45), or liver abscess scores (P = 0.41). Twenty-four implanted steers were selected from the original group of 140 and sorted into two slaughter groups of 12. Twelve implanted steers from each weaning group, matched in slaughter BW but differing in age, were subsampled at slaughter to assess the effect of weaning age and chronological age on muscle tenderness. Younger animals had lower Warner-Bratzler shear force values (P < 0.001) than older calves after 14 d of postmortem aging; however, no differences were found in tenderness after 21 d of aging. Furthermore, there was greater variance (P < 0.001) in Warner-Bratzler shear force values among younger, EW steers vs. older, TW steers. These data provide evidence that early weaning of beef calves may be used as a tool to more effectively manage the cow-calf production system without compromising the quality of the offspring.

Aging↗
PubMed2001

A comparative evaluation of conventional and pretargeted radioimmunotherapy of CD20-expressing lymphoma xenografts.

Radioimmunotherapy with anti-CD20 monoclonal antibodies is a promising new treatment approach for patients with relapsed B-cell lymphomas. However, the majority of patients treated with conventional radiolabeled anti-CD20 antibodies eventually have a relapse because the low tumor-to-blood and tumor-to-normal organ ratios of absorbed radioactivity limit the dose that can be safely administered without hematopoietic stem cell support. This study assessed the ability of a streptavidin-biotin "pretargeting" approach to improve the biodistribution of radioactivity in mice bearing Ramos lymphoma xenografts. A pretargeted streptavidin-conjugated anti-CD20 1F5 antibody was infused, followed 24 hours later by a biotinylated N-acetylgalactosamine-containing "clearing agent" and finally 3 hours later by (111)In-labeled DOTA-biotin. Tumor-to-blood ratios were 3:1 or more with pretargeting, compared with 0.5:1 or less with conventional (111)In-1F5. Tumor-to-normal organ ratios of absorbed radioactivity up to 56:1 were observed with pretargeting, but were 6:1 or less with conventional (111)In-1F5. Therapy experiments demonstrated that 400 microCi (14.8 MBq) or more of conventional (90)Y-1F5 was required to obtain major tumor responses, but this dose was associated with lethal toxicity in 100% of mice. In marked contrast, up to 800 microCi (29.6 MBq) (90)Y-DOTA-biotin could be safely administered by the pretargeting approach with only minor toxicity, and 89% of the mice were cured. These data suggest that anti-CD20 pretargeting shows great promise for improving current therapeutic options for B-cell lymphomas and warrants further preclinical and clinical testing.

Animals↗
PubMed2001

Intrasexual and intersexual dimorphisms of the red salmon prosencephalon.

Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are concerned with the position of the preoptic nucleus, nucleus lateralis tuberis, habenula, third ventricle, tectal ventricles, preoptic recess, recessus lateralis, horizontal commissure, posterior commissure, and toral commissure. The intrasexual dimorphism was characterized by either a rostral ("r"-pattern) or a caudal ("c"-pattern) position of the preoptic region as well as varying locations of other structures within the prosencephalon. As compared to "c"-pattern fish, the preoptic nucleus and nucleus lateralis tuberis were located more rostral, and the habenula was positioned further caudal, in "r"-type animals. The intersexual dimorphism was also characterized by different positions of the structures listed above. With the exception of the preoptic nucleus, all of these were located further rostral in "r"-pattern females than in type "r" males. In "c"-pattern females, they were positioned further caudal than in type "c" males. The number of neurons in the parvocellular and in the magnocellular portion of the preoptic region differed in the two genders with respect to "r"- as well as "c"-pattern fish. Males had more neurons than females in both the magno- and the parvocellular subdivisions of the preoptic region. In "r"- and "c"-pattern fish, the average size of magnocellular preoptic neurons was larger in females than in males. The observed intersexual variations may reflect gender-specific differences in the control of the pituitary. Functional correlates of intrasexual dimorphism are obscure.

Animals↗
PubMed2001

Reduced antibody response to streptavidin through site-directed mutagenesis.

Streptavidin provides an effective receptor for biotinylated tumoricidal molecules, including radionuclides, when conjugated to an antitumor antibody and administered systemically. Ideally, one would like to administer this bacterial protein to patients repeatedly, so as to maximize the antitumor effect without eliciting an immune response. Therefore, we attempted to reduce the antigenicity of streptavidin by mutating surface residues capable of forming high energy ionic or hydrophobic interactions. A crystallographic image of streptavidin was examined to identify residues with solvent-exposed side chains and residues critical to streptavidin's structure or function, and to define loops. Mutations were incorporated cumulatively into the protein sequence. Mutants were screened for tetramer formation, biotin dissociation, and reduced immunoreactivity with pooled patient sera. Patient antisera recognized one minor continuous epitope with binding locus at residue E101 and one major discontinuous epitope involving amino acid residues E51 and Y83. Mutation of residues E51, Y83, R53, and E116 reduced reactivity with patient sera to <10% that of streptavidin, but these mutations were no less antigenic in rabbits. Mutant 37, with 10 amino acid substitutions, was only 20% as antigenic as streptavidin. Rabbits immunized with either streptavidin or mutant 37 failed to recognize the alternative antigen. Biotin dissociated from mutant 37 four to five times faster than from streptavidin. Residues were identified with previously undescribed impact on biotin binding and protein folding. Thus, substitution of charged, aromatic, or large hydrophobic residues on the surface of streptavidin with smaller neutral residues reduced the molecule's ability to elicit an immune response in rabbits.

Amino Acid Sequence↗
PubMed2000

Comparative immunocytochemical study of FMRFamide neuronal system in the brain of Danio rerio and Acipenser ruthenus during development.

The distribution of FMRFamide-like immunoreactive (ir) neurons and fibers was investigated in the central nervous system of developing zebrafish and juvenile sturgeon (sterlet). Adult zebrafish was also studied. In zebrafish embryos FMRFamide-ir elements first appeared 30 h post-fertilization (PF). Ir somata were located in the olfactory placode and in the ventral diencephalon. FMRFamide-ir fibers originating from diencephalic neurons were found in the ventral telencephalon and in ventral portions of the brainstem. At 48 h PF, the ir perikarya in the olfactory placode displayed increased immunoreactivity and stained fibers emerged from the somata. At 60 h PF, bilaterally, clusters of FMRFamide-ir neurons were found along the rostro-caudal axis of the brain, from the olfactory placode to rostral regions of the ventro-lateral telencephalon. At 60 h PF, numerous ir fibers appeared in the dorsal telencephalon, optic lobes, optic nerves, and retina. Except for ir fibers in the hypophysis at the age of 72 h PF, and a few ir cells in the nucleus olfacto-retinalis (NOR) at the age of 2 months PF, no major re-organization was noted in subsequent ontogenetic stages. The number of stained NOR neurons increased markedly in sexually mature zebrafish. In adult zebrafish, other ir neurons were located in the dorsal zones of the periventricular hypothalamus and in components of the nervus terminalis. We are inclined to believe that neurons expressing FMRFamide originate in the olfactory placode and in the ventricular ependyma in the hypothalamus. On the same grounds, a dual origin of FMRFamide-ir neurons is inferred in the sturgeon, an ancestral bony fish: prior to the observation of ir cells in the nasal area and in the telencephalon stained neurons were noted in circumventricular hypothalamic regions.

Age Factors↗
PubMed2000

Sexually dimorphic distribution of galanin in the preoptic area of red salmon, Oncorhynchus nerka.

A sexually dimorphic distribution of galanin in the preoptic region of the molly and goldfish has previously been demonstrated. Females of these species lack galanin-immunoreactive perikarya in the preoptic nucleus. In contrast, we have found, in female red salmon, galanin-immunoreactive neurons in the magnocellular preoptic nucleus, located far lateral to the preoptic recess, whereas many immunoreactive fibers are present in the preoptic area in both genders. In addition, many immunoreactive neurons have been seen in the nucleus preopticus periventricularis and nucleus lateralis tuberis, also in both sexes. These findings support the notion that galanin may play a gender-specific role in red salmon.

Animals↗
PubMed2000

High-resolution correlation in apparently monotonous rocks: upper Ordovician Kope Formation, Cincinnati Arch.

Short stratigraphic sections in apparently monotonous strata pose several challenges to high-resolution (<l m) correlation. A lack of distinctive marker horizons can prevent obvious visual correlations between the sections. The stratigraphic shortness of the outcrops further reduces the likelihood of any given section having a recognizable marker horizon. The Upper Ordovician Kope Formation of the Cincinnati, Ohio, area exhibits both of these problems and correlation within the Kope has not been accomplished easily, to date. However, cross-correlation of meter-scale cycles in the Kope can be used to identify potential correlations of small outcrops to larger, well-described outcrops. If multiple correlations are equally plausible, large-scale faunal transitions among facies fossils can then be used to select the best correlation. In this pilot study, two sections separated by 9 km are correlated successfully using these methodologies, which show promise for the correlation of numerous outcrops in the Cincinnati area. In addition, the methods described here may be applied easily to other areas of limited outcrop in which the rocks are so complexly cyclic that they, likewise, appear to be monotonous.

Animals↗
PubMed1999

Distribution of FMRFamide-like immunoreactivity in the amphibian brain: comparative analysis.

FMRFamide is a small neuropeptide present in particular neurons of the basal forebrain and midbrain of the vertebrate groups studied, especially fishes and mammals. In order to assess interspecies variation, the distribution of FMRFamide-like immunoreactivity was studied in the brains of 13 species of amphibian. Although FMRFamide-immunoreactive (IR) terminals occurred throughout much of the brain, IR cell groups were noted in circumscribed regions of the CNS. In the eight anuran species studied, two major populations of labeled perikarya were observed: one in the septopreoptic area and another one in the caudal portion of the diencephalon. The rostrocaudal extent of both and the number of labeled somata in each neuronal group displayed species-specific differences. In urodeles and gymnophiones, labeled perikarya were located in the diencephalon, but there were remarkable species differences in the number of such cells. It is discussed whether sex or season of collection may account for some of the differences observed. The distribution of FMRFamide-IR perikarya, fibers, and pathways in the brain of anurans, urodeles, and gymnophiones was compared. The existence of FMRFamide perikarya in the anterior preoptic neuropil and medial septum appeared to be a feature common to all anurans; labeled neurons in the dorsal thalamus, however, may be present only in the (viviparous) gymnophione Typhlonectes compressicauda. Cerebrospinal fluid contacting FMRFamide neuronal cell bodies and fibers were observed in each of the three taxonomic orders. The data are compared with those previously obtained for other groups of vertebrates.

Amphibians↗
PubMed1999

Centrifugal Phe-Met-Arg-Phe-NH2-like immunoreactive innervation of the retina in a non-teleost bony fish, Lepisosteus osseus.

In all teleosts studied, Phe-Met-Arg-Phe-NH2- (FMRFamide-) like immunoreactive fibers originating from structures related to the olfactory system project to the retina. A complete report on this olfacto-retinalis projection in fish that are phylogenetically older than teleosts is still missing. We have visualized FMRFamide-like immunoreactive fibers in the optic nerve, the optic chiasm and in the retina of the longnose gar, Lepisosteus osseus. They terminate on amacrine or horizontal cells in the internal nuclear layer. Additionally, some of them appear to contact retinal ganglion cells.

Animals↗
PubMed1999

Comparative analysis of FMRFamide-like immunoreactivity in caiman (Caiman crocodilus) and turtle (Trachemys scripta elegans) brains.

The distribution of FMRFamide (FMRFa)-like peptides in caiman (Caiman crocodilus) and turtle (Trachemys scripta elegans) brains was studied by immunohistochemistry. In both species, distinct groups of FMRFa-like immunoreactive (ir) perikarya were present in the medial septal nucleus, accumbens nucleus, nucleus of the diagonal band of Broca, suprachiasmatic area, lateral hypothalamic area, and periventricular hypothalamic nucleus. A few FMRFa-ir neurons in the hypothalamic area were located in the neuroepithelial cell lining of the third ventricle. FMRFa-ir fibers were scattered in all major areas of the brain, from the olfactory bulbs to the rhombencephalon. They formed dense aggregates in the medial septal area, basal telencephalon, median eminence, and infundibulum, and adjacent to the fourth ventricle. The most obvious difference between the FMRFa-ir systems in caimans and turtles concerned the number of nuclei that contained neurons with this immunoreactivity. Eight such clusters were present in the caiman brain, whereas thirteen clusters were found in the turtle brain. The turtle also displayed scattered FMRFa-ir somata in the anterior olfactory nucleus, striatum, lateral septal nucleus, medial and lateral cortex, medial forebrain bundle, lateral preoptic area, and lateral geniculate nucleus. In the caiman brain, a few FMRFa-ir neurons were noted in the ventrolateral area of the pallial commissure and an even smaller number of ir neurons was found dispersed in the optic tracts. Neither formed nuclear aggregates. The results are compared with those described for other vertebrates.

Alligators and Crocodiles↗
PubMed1999

Primary cesarean section rates in uninsured, Medicaid and insured populations of predominantly rural northern New England.

Many studies in the United States during the past two decades have reported consistently lower cesarean section rates in women of lower socioeconomic status as defined by census tract, insurance status, or maternal level of educational attainment. This study sought to determine whether cesarean section rates in predominantly rural northern New England are lower for lower, compared with higher socioeconomic groups, as they are reported nationally and in more urban areas. Age-adjusted, primary cesarean section rates for privately insured, Medicaid and uninsured women were calculated using 1990 to 1992 uniform hospital discharge data for Maine, New Hampshire and Vermont. Age-adjusted cesarean section rates for insured women (15.71 percent) were significantly higher than those for Medicaid (14.35 percent) and uninsured (12.85 percent) women. These differences in the cesarean section rate between the insured and poorer populations in northern New England are much less than those reported elsewhere in the country.

Age Distribution↗
PubMed1999

NADPH-diaphorase expression in the hypothalamo-hypophysial system of different catfish.

The distribution of NADPH-d activity was studied in the hypothalamus and in the pituitary gland of 15 species of catfish. Seven hypothalamic nuclei, four fiber bundles, as well as cells located in the adenohypophysis were labeled by NADPH-d histochemistry. Reactive somata were found in the nucleus praeopticus periventricularis, the paraventricular division of the nucleus praeopticus, the supraoptic division of the nucleus praeopticus, the nucleus lateralis tuberis, the paraventricular organ, the nucleus recessus lateralis, the nucleus recessus posterioris, and in the adenohypophysis. In some species, an inconsistent number of these structures lacked NADPH-d activity. These results are compatible with the notion that NADPH-d activity expressing cells in the hypothalamus and in the pituitary are involved in the control of hormone regulation.

Animals↗
PubMed1998

Comparative analysis of GnRH neuronal systems in the amphibian brain.

We have investigated the GnRH-ir neuronal systems in the brain of the oviparous urodele, Triturus vulgaris, ovoviviparous urodele, Salamandra salamandra, and viviparous caecilian, Typhlonectes compressicauda, and have reexamined Xenopus laevis, Ambystoma mexicanum, and Rana esculenta. Results showed that mGnRH neuronal system was diffused along the medioventral telencephalon and diencephalon with the numerical preponderance of GnRH cell bodies in the rostral mediobasal telencephalon in T. vulgaris and S. salamandra and in medial septal area and preoptic area respectively in Typhlonectes compressicauda and X. laevis. The cGnRH-II-ir perikarya were restricted to the midbrain tegmentum in X. laevis and T. compressicauda. In T. vulgaris, two distinct groups of cGnRH-II neurons were distinguished, one in the midbrain tegmentum and another in the paraventricular organ. The former was composed of comparatively bigger perikarya than the latter. In X. laevis brain, besides those in the rostralmost dorsomedial and ventromedial telencephalon and septopreoptic area, mGnRH neurons were also found in the habenulae and habenular commissure as well the infundibular hypothalamus. In A. mexicanum, reexamined, the preoptic area-located mGnRH neurons were distributed in the ependymal lining of the preoptic recess. In this neotenic urodele, furthermore, cGnRH-II neurons were also present in the rhombencephalon, as well as in the infundibular hypothalamus. It is thus clear that while GnRH-ir cell bodies are distributed in the fore-, mid- and hindbrain, their precise neuroanatomical localization varies somewhat within and among groups. Altogether, it is evident that mGnRH neuronal system is confined mainly to the forebrain, whereas cGnRH-II system is commonly found in the mid- and hindbrain. Additional morphological investigations are required to eventually define the functional neuroanatomy of GnRH in the amphibian brain.

Amphibians↗
PubMed1997

Differential labelling of primary olfactory system subcomponents by SBA (lectin) and NADPH-d histochemistry in the frog Pipa.

SBA and NADPH-d histochemistries allow identification of functionally distinct components of the amphibian primary olfactory system. In Pipa, a secondarily aquatic frog, combination of both methodologies, using alternate sets of histological sections, reveals that, apart from Jacobson's organ, this species has a "water-nose" and an "air-nose". The epithelia occupy separate chambers of the olfactory organ and give rise to olfactory nerve fiber bundles that are identified by the dual staining procedure.

Adaptation, Physiological↗
PubMed1997

Cycle anatomy and variability in the storm-dominated type cincinnatian (Upper Ordovician): coming to grips with cycle delineation and genesis.

Although parasequence and sequence are scale-independent terms, they are frequently applied only to specific scales of cycles. For example, meter-scale cycles are commonly assumed to be parasequences or PACs. In the Upper Ordovician Kope and Fairview Formations of northern Kentucky, we examined a succession of 50 meter-scale cycles that have been variously interpreted as deepening-upward, shallowing-upward, or showing no relationship with water depth. Our analysis shows that these cycles, characterized by shifts in storm-bed proximality, are highly variable in their thickness and internal construction. Most cycles are best considered high-frequency sequences, because deepening-upward intervals are common, and many cycles contain evidence of abrupt basinward shifts in facies as expected at sequence boundaries. A minority fit the parasequence model of shallowing-upward cycles bounded by flooding surfaces. Larger, 20 m scale cycles are defined by systematic thickening and thinning trends of meter-scale cycles. However, meter-scale cycles do not display any systematic trends in cycle anatomy as a function of position within the 20 m cycles or position within the Kope and Fairview Formations. The high cycle variability and the lack of systematic stratigraphic organization with respect to longer-term cyclicity reflect either the irregularity of relative sea-level changes, the poor recording of sea-level changes in this deep-water setting, or the generation of these cycles by climate-induced cyclicity in storm intensity. These three mechanisms would generate similar patterns at the outcrop scale, so it is not possible at the present to distinguish between them.

Factor Analysis, Statistical↗
PubMed1997

LiCl-induced malformations of the eyes and the rostral CNS in Xenopus laevis.

Ocular malformations such as synophthalmia and cyclopia occur in all vertebrates including humans. We induced fused eye anlagen by exposure of Xenopus laevis embryos to dissolved LiCl. Three basic forms of malformations were observed in the rostral CNS; these represent major steps in a continuous sequence of ocular abnormalities: (i) "hour-glass eyes", (ii) synophthalmia, and (iii) cyclopia vera. The type of abnormity induced seemed to depend on the time and/or the dosage of LiCl exposure. In all cases studied, the histology of the retinae was normal. We reconstructed olfactory organs, eyes, and rostral portions of the CNS from serial sections of 16 Xenopus larvae. Our results confirm that defective bilateralization affects all parts of the rostral CNS and suggest that the telencephalon displays the weakest, and the eyes have the highest, resistance against midline fusion. Defective bilateralization also involves the pineal anlagen, as duplication or enlargement of the pineal organs occurred in most cases with ocular fusion. We conclude that LiCl-induced interferences with ontogenetic bilateralization of prosencephalic structures are the consequence of an elimination of an, as yet, undefined bilateralization signal from (ventral) midline structures of the neural plate and tube.

Abnormalities, Drug-Induced↗