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Biomedical subjects

M M Beck

Publications and source records attributed to M M Beck.

18 recordsLinked to original sources
PubMed1995

Development of metabolic response in male quail brain during sexual maturation.

Seasonal reproductive activities of Japanese quail Coturnix japonica are induced most obviously by stimulatory effects of long-day photoperiod. This study addressed the metabolic response, as measured by 2-deoxyglucose (2-DG), in brain of male quail during sexual maturation. At 7 weeks of age, reproductively quiescent quail exposed to a short photoperiod of 6L:18D, received 2-DG on day 0 and +3, +6, +9, +12, +15 and +18 days after onset of 16L:8D. Brains were processed for autoradiography; serum testosterone was measured to indicate reproductive response to photoperiod. Circulating testosterone remained low until day 9, then rose sharply, reaching maximum levels at day 18. Heavily labeled nuclei were identified in some discrete neural pathways: both tectofugal and thalamofugal visual pathways, ascending auditory pathway, efferent vocalization pathway, and limbic structures. Metabolic activity of the terminal nucleus (ectostriatum) of the tectofugal pathway increased significantly by day 18, but in the terminal nuclei (the Wulst) of the thalamofugal visual pathway activity did not change significantly. Energy metabolism of some nuclei of the auditory pathway rose significantly by day 3, although in the vocal pathway it did not show augmentation until days 15-18. The metabolic activity of limbic structures also increased. These results suggest that, in Japanese quail, sensory nuclei and some of their integrative areas become sensitive to environmental cues in response to long-day photoperiod. It is possible that the external environmental cues that affect the reproductive activities of quail act through sensory systems.

Animals↗
PubMed1994

Elevated brain GABA correlates with systemic dysfunctions in paroxysmal chick.

Altered brain GABA, phosphocreatine and adenosine triphosphate have been documented in paroxysmal (px) chicks in earlier studies, suggesting perturbations in energy metabolism as a causative factor in this syndrome that is characterized by spontaneous neural degeneration of several central sensory systems, grand mal seizures, and progressive anorexia. In this study, brain sections from 5-, 7-, and 10-day-old px and normal White Leghorn-cross chicks were stained by immunocytochemistry to localize and quantify GABA. Serum glucose was measured to assess adequacy of circulating energy substrate. Differences between px and normal brains were found in GABA staining intensity in nuclei and tracts associated with auditory, vestibular and oculomotor function, and in several septal areas. Staining appeared to be confined primarily to terminals, and increasingly larger numbers of stained terminals were found in older px brains. This progressive increase appears to parallel the degenerative changes that occur over time in px brain and progressive manifestation of clinical signs. Px chicks appear to have adequate circulating glucose, suggesting that alterations in brain energy substrates are not a function of inadequate supply.

Age Factors↗
PubMed1991

Characteristics of the interaction of the ferritin repressor protein with the iron-responsive element.

The iron-responsive regulation of ferritin mRNA translation is mediated by the specific interaction of the ferritin repressor protein (FRP) with the iron-responsive element (IRE), a highly conserved 28-nucleotide sequence located in the 5' untranslated region of ferritin mRNAs. The IRE alone is necessary and sufficient to confer repression of translation by FRP upon a heterologous message, chloramphenicol acetyltransferase, in an in vitro translation system. The activity of FRP is sensitive to iron in vivo. Cytoplasmic extracts of rabbit kidney cells show reduction of FRP activity when grown in the presence of iron, as detected by RNA band shift assay. Using a nitrocellulose filter binding assay to examine the interaction of FRP with the IRE in more detail, we find that purified FRP has a single high-affinity binding site for the IRE with a Kd of 20-50 pM. Hemin pretreatment decreases the total amount of FRP which can bind to the IRE. This effect is dependent on hemin concentration. Interestingly, the FRP which remains active at a given hemin concentration binds to the IRE with the same high affinity as untreated FRP. A variety of hemin concentrations were examined for their effect on preformed FRP/IRE complexes. All hemin concentrations tested resulted in rapid complex breakdown. The final amount of complex breakdown corresponds to the concentration of hemin present in the reaction. The effect of hemin on FRP activity suggests that a specific hemin binding site exists on FRP.

Animals↗
PubMed1991

Plasma progesterone, luteinizing hormone concentrations, and granulosa cell responsiveness in heat-stressed hens.

Plasma progesterone and luteinizing hormone (LH) profiles were obtained during the first ovulatory cycle of heat-stressed (HS, 35 C; n = 24) and unstressed (US, 17 to 27 C; n = 24) hens using 30-min sampling intervals beginning approximately 6 h prior to ovulation. Progesterone levels from HS hens were lower from 6 h [.07 +/- .01 (SE) versus 1.66 +/- .25 ng/mL; P = .008] to predicted ovulation (.06 +/- .006 versus .70 +/- .18 ng/mL; P = .07). Likewise, LH levels from HS hens were lower from 6 h (1.55 +/- .16 versus 3.86 +/- .34 ng/mL; P = .007) to predicted ovulation (1.63 +/- .18 versus 2.50 +/- .27 ng/mL; P = .01). Eggs from HS hens were more often laid early (less than 24 h) than eggs from US hens (71.42 versus 13.33%, respectively; P = .01), but US hens more often laid eggs of a normal oviposition interval length (24 to 26 h) compared with HS hens (73.34 versus 14.29%; P = .0005). The percentage of delayed eggs (greater than 26 h) was not different (US, 14.29 versus HS, 13.37%; P = .75) between the two treatment groups. Basal production of progesterone by dispersed granulosa cells from US hens was 97.62 +/- 16.01 ng/mL. Challenge by LH increased this to 417.50 +/- 53.38 ng/mL (P = .0001). In contrast, basal progesterone secretion by cells from HS hens was 40.25 +/- 6.60 ng/mL (P = .0001) and LH challenge failed to increase progesterone production.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

CSF ion composition and manipulation during thermoregulation in an avian species, Gallus domesticus.

1. At thermoneutrality (28 degrees C), CSF Na+:Ca2+ in hens was 61.66; under thermal stress (39 degrees C), it changed to 59.38 (30 min), 62.58 (3 hr), and 52.44 (10 hr); no change in ratio occurred at 15 degrees C. 2. ICV Ouabain and/or EGTA increased body temperature (TR) but not respiration rate (RR) at 39 degrees C. 3. At 28 degrees C, Ouabain decreased, and EGTA increased, TR and RR. 4. Ca2+ may be more critical than Na+ in thermoregulation. 5. Heat stress appears to stimulate Na+-transport mechanisms other than Na+-ATPase. 6. RR appears to be a function of TR, not of ion balance.

Animals↗
PubMed1988

Thermoregulatory responses of laying hens under cyclic environmental temperature to intraventricular calcium and sodium.

1. Hens received ICV injections of Ca2+ (1.98 g/100 ml) or Na+ (7.25 g/100 ml) at 28 degrees C and, following acclimation, at 37 or 20 degrees C, respectively. 2. At 28 degrees C (thermoneutrality), rectal temperature rose (P less than 0.05) following Na+ and fell (P less than 0.05) following Ca2+, similar to mammals and broiler chickens. 3. At 37 degrees C, Ca2+-induced hypothermia did not occur; nor did the Na+-associated hyperthermia at 20 degrees C. 4. Acclimation to a high or low temperature may produce an endogenous shift in CSF ion levels that make additional ion administration ineffective in affecting body temperature.

Animals↗
PubMed1987

Peripheral and brainstem auditory function in paroxysmal (px) White Leghorn chicks.

The paroxysmal (px) chick is a mutant White Leghorn (Gallus domesticus) which appears normal at hatching and during the subsequent week. By ca. 8 days posthatching, various symptoms develop, of which the most obvious are depressed food intake (anorexia) and audiogenic seizures. Histological evidence suggests that central auditory and vestibular nuclei and fiber tracts begin to degenerate prior to seizure onset. This degeneration, which affects central and peripheral components of both systems, becomes increasingly severe over time although auditory stimulation continues to elicit seizures. Characterization and analysis of peripheral and brainstem auditory response to auditory stimuli indicated that major response differences between px and normal chicks exist in peaks reflecting brainstem activity (P3A, P3B, P4A, P5A). In 5 of 8 px chicks, these later response peaks were either grossly abnormal in terms of amplitude and latency (including amplitude input/output functions) or often entirely absent. Early peaks (P1A and P2A), however, in px waveforms were normal in morphology and amplitude, indicating normal function of peripheral auditory structures. Although lower body temperature of px chicks may account for some of the longer latencies observed, other abnormalities (e.g. absence of peaks) could not be produced in normal birds by induced hypothermia.

Animals↗
PubMed1987

Origins of peripheral and brainstem auditory responses in the White Leghorn chick.

1. Peripheral and central auditory projections were sectioned and far-field recordings measured to determine neural generators of the waveform in the White Leghorn chick. 2. The mesencephalicus lateralis p. dorsalis and more rostral structures do not contribute to the waveform. 3. Activity of N.VIII is reflected in peaks P1A and P2A; N2A appears to be central in origin but may be in part from the central stump of N.VIII. 4. The crossed dorsal cochlear tract but not the trapezoid body is necessary for P3A and P4A; it is therefore functionally homologous to mammalian trapezoid fibres. 5. P1A, P2A, N2A, P2B are not dependent on crossing fibres.

Acoustic Stimulation↗
PubMed1987

Far-field recordings of short latency auditory responses in the White Leghorn chick.

Far-field recordings of short latency auditory responses were characterized in the White Leghorn chick (Gallus domesticus, 2-3 weeks post hatch). Six to twelve positive peaks were normally present within the first 8 ms following the onset of a click stimulus (stimulus intensity = 99.0 +/- 6.3 dB pe SPL, 44.3 +/- 1.2 dB SL). Both cochlear microphonic (CM) and neural response components were distinguished based on functional criteria. Neural responses (P1a-P6b) were readily masked by white noise. CM responses were resistant to masking and inverted when click polarity was reversed. Systemic cooling produced shifts in neural response latencies such that later peaks (e.g. latencies greater than or equal to P3) were delayed to a greater extent than early peaks (P1a and P2a). The latencies of CM components were relatively unaffected by cooling. The mean latencies and amplitudes were described quantitatively for dominant positive peaks. The mean auditory response threshold for 18 animals was 54.5 +/- 7 dB pe SPL. Dominant later components (P3a and the P3b/P4a complex) were the first to disappear after lethal injection of anesthetic. These were followed immediately by earlier neural peaks. CM components were the last to disappear. A working hypothesis is advanced regarding the distinction between central (P3a, P3b and P4a) and peripheral (P1a, P2a) neural components.

Animals↗
PubMed1986

Effect of serial blood sampling on interpretation of estradiol-17 beta involvement in laying hen calcium metabolism.

Effects of long-term, low levels of exogenous estradiol-17 beta and dietary calcium on calcium metabolism and laying hen performance, and effects of serial blood-sampling, were studied. Significant 3-way (P less than 0.01) and 2-way (P less than 0.05) interactions involving sampling obscured possible main effects (Exp. 1); no main effects were found in absence of blood sampling (Exp. 2). Estradiol-17 beta appears to increase calcium utilization with very low dietary calcium only. Relatively small brachial vein samples taken only every 3-4 weeks have substantial confounding effects on interpretation of data.

Animals↗
PubMed1986

Influence of stimulus polarity on far-field auditory-evoked electrical responses in the chick.

The effects of inverting click phase on far-field peripheral and brainstem auditory-evoked responses (PBARs) were examined in 8 White Leghorn chicks of age 3 wks. Significant latency differences occurred in all major positive peaks (Pla, P2a peripheral; P3a central) in response to rarefaction vs condensation clicks of equal intensity, with condensation clicks producing the shortest latencies (latency differences: Pla = 0.374, P2a = 0.372 and P3a = 0.352 msec, p less than .001). The mean latency shift corresponds to an equivalent sine wave frequency of approximately 1360 c/s, a value close to the spectral peak energy of the click. No differences in interpeak latency values were found nor any significant amplitude effects.

Acoustic Stimulation↗
PubMed1985

Energy metabolism in audiogenically seizure-prone chicks.

Female chicks carrying the lethal, sex-linked recessive paroxysmal (px) gene are susceptible to spontaneous and audiogenic seizures. Because seizure activity does not begin until 1 to 2 weeks posthatching - coincidental with disappearance of the yolk-sac - it is postulated that a contributing factor to seizure activity may be a developmental failure of the chick's ability to switch from lipid to carbohydrate as a primary energy source. In testing this hypothesis, three experiments were performed: 1) to evaluate cerebral energy reserves - adenosine triphosphate (ATP), phosphocreatine - of px and normal chicks; 2) to determine effects of energy source (ethanol, glucose, insulin, and glucose-insulin combined) on audiogenically-induced seizure activity and electrical seizure threshold; 3) to evaluate energy source utilization as estimated by the respiratory quotient (RQ). Brain ATP and phosphocreatine levels in px chicks were both decreased (P less than .05) as early as 10 days posthatching. Ethanol increased electrical seizure threshold in 50% of px chicks and provided protection from audiogenic stimulation. No consistent effect was found with any of the other substances. The RQ of px chicks were lower (P less than .05) than those of controls by 18 days posthatching.

Acoustic Stimulation↗
PubMed1985

Effect of atmospheric ammonia on the surface ultrastructure of the lung and trachea of broiler chicks.

The surface ultrastructure of the lung and trachea of 7-week-old broiler chicks were examined with scanning electron microscopy (SEM) to obtain a more accurate understanding of structural changes due to atmospheric ammonia (NH3). In the first experiment, four broilers were randomly assigned to each of four chambers, and exposed to 0, 25, 50, 75, or 100 ppm NH3 for 7 days. Chickens exposed to 100 ppm NH3 exhibited a large number of mucus-secreting cells that were not seen in the other treatments. Ciliary loss from the tracheal epithelium was not a consistent finding in either the exposed or the control groups. There was no evidence of goblet cell disappearance due to ammonia treatment. In the second experiment, four broilers were randomly allocated to each of four chambers and exposed to 0, 50, 75, or 100 ppm NH3 for 4 days. There was an increase in the thickness of the atrial walls and a shrinking of air capillaries with increasing NH3 concentration; in birds exposed to 75 and 100 ppm NH3, wall thickness was one to two times greater than in the control birds. There were no observable differences in gross appearance of lungs and tracheas between control and exposed groups except for hemorrhagic spots on one of the lungs exposed to 100 ppm NH3.

Air Pollutants↗
PubMed1984

GABA in brain tissue of paroxysmal (px) chick.

An investigation was made of GABA in whole brain and brain regions of paroxysmal (px) chicks. Whole brain levels of GABA were higher (P less than 0.05) in px chicks than in normal siblings by day 10 post-hatching. GABA in brain areas containing degeneration of auditory and vestibular nuclei and tracts was also found to be higher (P less than 0.05) in px chicks. These data indicate that a dysfunction of the GABA pathway occurs early in the px syndrome, possibly as a causative factor.

Animals↗
PubMed1983

Auditory and vestibular pathology of seizure-prone chicks.

The mutant sex-linked lethal recessive px (paroxysmal) gene, expressed in White Leghorn chicks (Gallus domesticus) causes seizures beginning on approximately day 8 post-hatching. Seizures are spontaneous and inducible by auditory but not by photic stimulation. Prior to seizure onset px chicks are indistinguishable from non-px siblings. With seizure onset is a decrease in food intake which causes deterioration and death by 4-10 weeks of age. In a preliminary histological study conducted on 22-day-old seizure-prone chicks, brains were perfused and sections treated according to a modified cupric-silver staining technique. Nuclei and fiber tracts of px auditory and vestibular systems were extensively degenerated; control brains showed essentially no degeneration. A second experiment was conducted with preseizure chicks to determine whether and to what extent degeneration occurs prior to seizure onset. Deep nuclei of px cerebellum appeared to be the first seriously affected (5 days of age). Extent of degeneration progressed steadily over time through 20 days of age, by which time all components of the two sensory systems were maximally affected. Ambient noise did not affect onset or extent of degeneration, nor did it affect onset of seizures.

Acoustic Stimulation↗
PubMed1983

Implication of iron in seizure syndrome of mutant chicks (Gallus domesticus).

1. An investigation was made of systemic iron in paroxysmal (px) chicks. 2. Serum transferrin levels in px chicks are greatly increased (P less than 0.05) over control levels, but iron-binding capacity is decreased (P less than 0.05). 3. The delayed (by 10 days) increase in px hemoglobin (P less than 0.01) may be due to the general debilitation seen in px syndrome. 4. An attempt to determine brain iron showed no deposits comparable to mammalian brain iron distribution, but this was consistent with inability of others to locate iron in adult chicken brain tissue.

Animals↗
PubMed1978

Predicting clinical performance: a two-step approach.

This paper presents the results of a two-year study on the predictive value of the Spatial Relations Test of the Differential Aptitude Test (SRTDAT) for grades in dental hygiene laboratory and clinical courses. The data indicate the SRTDAT was a statistically significant predictor of early laboratory product performance, and this performance was predictive of final clinical performance.

Adult↗