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Biomedical subjects

M S Blumberg

Publications and source records attributed to M S Blumberg.

At least 19 recordsLinked to original sources
PubMed1997

Thermogenic, respiratory, and ultrasonic responses of week-old rats across the transition from moderate to extreme cold exposure.

Previously, it was reported that week-old rats exposed to air temperatures that elicited submaximal levels of heat production (designated moderate cold exposure) remained asleep and did not vocalize (Blumberg & Stolba, 1996). In contrast, pups exposed to air temperatures that elicited maximal levels of heat production (designated extreme cold exposure) woke up and emitted ultrasonic vocalizations. We now report on the physiological and behavioral responses of pups in the transitional region between moderate and extreme air temperatures. Small decreases in air temperature across the transition resulted in pronounced decreases in physiological temperature and concomitant increases in ultrasound production. In a second experiment, it was shown that during moderate cold exposure respiratory frequency increased as air temperature decreased but, as extreme air temperatures were reached, respiratory frequency was maximized as ultrasound production began. The results from these two experiments illustrate how air temperatures that differ by as little as 2 degrees C can differentially modify the physiological and behavioral responses of neonates.

Animals↗
PubMed1997

Brown fat thermogenesis and cardiac rate regulation during cold challenge in infant rats.

Infants rats depend on heat production by brown adipose tissue (BAT) during cold challenge. Although it has been suggested that BAT thermogenesis protects the heart in the cold, the relationship of BAT activation to cardiac rate has not been examined directly. In the first experiment, the cardiac rate of 2- and 7- to 8-day-old rat pups was monitored during moderate and extreme cold challenge. Pups at both ages maintained cardiac rate during moderate cold challenge while BAT thermogenesis was increasing. In contrast, cooling to air temperatures at which BAT thermogenesis could increase no further resulted in pronounced bradycardia. In the second experiment, ganglionic blockade was used to eliminate BAT heat production and autonomic control of the heart in 7- to 8-day olds. Blockade suppressed BAT thermogenesis in the cold and led to pronounced decreases in interscapular temperature and cardiac rate. These data suggest that cardiac rate in infant rats is modulated both by the autonomic nervous system and BAT thermogenesis.

Acclimatization↗
PubMed1996

A developmental and component analysis of active sleep.

A wide variety of hypotheses have been put forth that address the functional significance of active sleep. Despite the well-accepted fact that active sleep expresses itself predominantly in the perinatal period, the vast majority of these functional hypotheses are applicable largely, if not exclusively, to the adult. We build on the developmental approaches of previous researchers and propose that the individual components of active sleep (e.g., myoclonic twitches, rapid eye movements) exhibit unique developmental and phylogenetic histories and may serve independent functions in the developing organism. This dynamic perspective leads to specific experimental approaches aimed at the developmental roles of these components in the neonate, their maintenance roles in the adult, and the means by which these various components coalesce temporally in what is commonly referred to as a behavioral state.

Adolescent↗
PubMed1996

Thermogenesis, myoclonic twitching, and ultrasonic vocalization in neonatal rats during moderate and extreme cold exposure.

Physiological and behavioral responses of 2- and 7-8-day-old rats were monitored during moderate and extreme cold exposure. During moderate cold exposure (30 degrees C < or = air temperature < or = 32.5 degrees C), pups at both ages increased heat production, maintained an elevated interscapular temperature, and maintained baseline levels of myoclonic twitching, a behavior commonly associated with active sleep. During extreme cold exposure (21 degrees C < or = air temperature < or = 25 degrees C), pups at both ages continued producing metabolic heat, but now exhibited pronounced decreases in interscapular temperature and decreased rates of myoclonic twitching. Furthermore, the 7-8-day-old pups exhibited significant increases in ultrasound production, and males vocalized more than females. These results suggest the presence of a narrow subthermoneutral zone in neonates in which nonshivering thermogenesis is regulated and sleep-related behaviors are protected.

Acclimatization↗
PubMed1995

Pontine and basal forebrain transections disinhibit brown fat thermogenesis in neonatal rats.

Bignall, Heggeness and Palmer (1975) were the first to demonstrate increases in metabolic heat production following midpontine transection in neonatal rats. Subsequent work in adult rats has shown that this procedure disinhibits thermogenesis by brown adipose tissue (BAT). Bignall and his colleagues also found that hypothalamic ablation did not result in increased thermogenesis in 5-day-olds, leading them to conclude that thermoregulation depends on more caudal structures at that age. We have also found that midpontine transection disinhibits BAT thermogenesis and, furthermore, have extended that finding to newborn pups. When transections were made in the basal forebrain, however, we also found profound and rapid increases in brown fat thermogenesis. These results suggest the presence of at least two sources of inhibition of BAT thermogenesis in newborn rats: one located in the rostral pons-caudal midbrain and one located in the basal forebrain.

Adipose Tissue↗
PubMed1995

Animal mind and the argument from design.

The argument from design has played an important role in the history of philosophy and biology. Paley, the 19th-century theologian, was struck by the bodily complexity and adaptive fit of animals to their environments; he used the argument from design to prove the existence of God. Darwin, however, provided the natural evolutionary mechanisms that eliminated the need for positing a divine creator to explain the structure of animals; he was thus able to treat the historical problem of organic evolution by providing a historical solution. Today, some students of behavior are similarly struck by the complexity of animals' actions and their adaptive fit to the environment. Like Paley, they use the argument from design, but to prove the existence of a conscious designer inside the head of the animal--the mind. This mentalistic approach suffers from many of the philosophical and empirical problems that plagued similar efforts in the past.

Animals↗
PubMed1995

Seeing and knowing: knowledge attribution versus stimulus control in adult humans (Homo sapiens).

Interest in cognition in nonhuman animals has inspired new approaches to discovering animals' ability to attribute knowledge to others (e.g., D. J. Povinelli, K. E. Nelson, & S. T. Boysen, 1990). The assumptions of such experiments were tested in this study by training a group of humans (Homo sapiens) to use accurate information provided by a confederate who was watching as 1 container among 4 was baited; a 2nd group was similarly trained to use accurate information provided by a confederate whose back was turned during baiting. On a single reversal trial, the roles of the 2 confederates were switched. Subjects were able to learn their respective tasks but attended to different aspects of the confederates, as revealed by the reversal trial. Although attributional interpretations can be applied to such data, many of the choices in this experiment can be explained more readily with the basic principles of contingency-based learning.

Adolescent↗
PubMed1994

Dual mechanisms of twitching during sleep in neonatal rats.

Twitches of the limbs during REM sleep in adult mammals result from descending motor activation from the brainstem. In contrast, many spontaneous movements in embryos appear similar to REM-related twitches and result from the local firing of spinal motor neurons. To determine which mechanism produces twitches in neonates, we analyzed twitching in 5- and 8-day-old rat pups that had spinal cords transected in the lower thoracic region. This transection separated motor units controlling forelimb movements from motor units controlling hindlimb movements. Spinal transection did not significantly affect the amount of forelimb twitching. In contrast, the amount of hindlimb twitching in transected pups was reduced by only 35%-50%. Given that hindlimb twitching was not eliminated by spinal transection, it is concluded that there are 2 independent mechanisms producing twitches at these ages.

Animals↗
PubMed1994

Impact of extending health care coverage to the uninsured.

Changes in use of health services by the uninsured, when covered after health reform, are a key to the costs of reform. From data on persons under age sixty-five in the 1989 National Health Interview Survey, we estimated their expected use of hospitals (excluding obstetric deliveries) and doctor visits, adjusting for age, sex, and self-reported health status. If uninsured persons obtained private coverage distributed by the plan type of other persons in their home regions, nonobstetric hospital days for the formerly uninsured would increase 28 percent, and their visits to physicians' offices would increase 52 percent. If instead the uninsured enrolled entirely in group- or staff-model health maintenance organizations (HMOs) in their home regions, their nonobstetric hospital days would actually decrease 17 percent, and their visits to physicians' offices would increase 60 percent.

Adult↗
PubMed1992

Ultrasonic vocalizations by rat pups: the primary importance of ambient temperature and the thermal significance of contact comfort.

We investigated the effects of isolation, huddling, and air temperature on ultrasound production by rat pups. Experiment 1 showed that ultrasound production by 8- to 9-day-olds was minimal at thermoneutrality and increased in response to small deviations of air temperature on either side of the thermoneutral zone. Experiments 2 and 3 showed that suppression of ultrasound production by contact with littermates is consistent with the thermal consequences of huddling. Experiment 4 showed that, contrary to previous conclusions, ultrasound production is not independent of ambient temperature in pups older than 10 days of age. Taken as a whole, these experiments emphasize (1) the importance of ambient temperature for the elicitation of ultrasound by rat pups of all ages studied, (2) the importance of thermal factors in the suppression of ultrasound by littermate contact, and (3) the manner in which different methods can change interpretations of the behavior and physiology of infant rats.

Animals↗
PubMed1992

Thermogenesis during ultrasonic vocalization by rat pups isolated in a warm environment: a thermographic analysis.

Ultrasonic vocalizations, emitted by rat pups when separated from their mother, littermates, and home cage, have been used as a measure of isolation distress. Recently, we demonstrated that cold exposure is the primary component of isolation that induces the vocalization. We were unable, however, to suppress all ultrasound production when transferring pups to a thermoneutral (35 degrees C) environment. Using an infrared thermography system that allows us to estimate noninvasively heat production by brown adipose tissue, we found that pups transferred from the home nest to a 35 degree C test chamber exhibited sizable levels of heat production while they were vocalizing. Moreover, both heat production and ultrasound emission decreased over the 15-min test. Next, we used extreme care to minimize thermal, and therefore respiratory, stimulation of pups before, during, and after the transfer procedure. We found that such precautions prevented both heat production and ultrasound emission following transfer. These results indicate that infant rats' thermal sensitivities are far greater than previously suspected.

Adipose Tissue, Brown↗
PubMed1992

Rodent ultrasonic short calls: locomotion, biomechanics, and communication.

Rodents of many species emit short ultrasonic vocalizations during copulation, aggression, and other activities. Thiessen and Kittrell (1979) hypothesized that ultrasound emission by gerbils is the acoustic by-product of physical compression of the thorax during certain locomotor behaviors. I carry this hypothesis further by relating gerbil ultrasound to the biomechanics of respiration during locomotion. I also suggest that at least some of the ultrasonic emissions of other rodent species are, like the gerbil's, by-products of thoracic compression during locomotion. Support for this suggestion comes from descriptions in the literature of ultrasound emission as well as slow-motion analysis of rat copulatory behavior. Finally, this alternative view of rodent ultrasound has consequences for the interpretation of experimental findings in ultrasound research and for the understanding of messages and meanings in rodent communication.

Animal Communication↗
PubMed1991

Biased estimates of expected acute myocardial infarction mortality using MedisGroups admission severity groups.

This study examines whether the MedisGroups admission severity groups give unbiased estimates of 30-day mortality in 3037 Medicare-aged patients who were hospitalized in 1985 through 1986 with acute myocardial infarction. The average observed death rate for all acute myocardial infarction patients in the study who were in a given admission severity group was used to estimate the expected death probability for each case in a given group. (This is the same method used by the Pennsylvania Health Care Cost Containment Council for risk adjusting hospital mortality by diagnosis related groups in that state.) When compared with observed deaths, estimates of expected mortality were significantly biased for many patient attributes (eg, age, location of acute myocardial infarction, history of congestive heart failure, serum potassium level, serum urea nitrogen level, pulse rate, and blood pressure). These results are consistent with a conclusion that the MedisGroups scoring algorithm omits some important risk variables, inappropriately includes some other variables reflecting postadmission status, and gives the wrong weights to some appropriate risk variables. To the extent that these findings are also applicable to current MedisGroups scoring algorithms and to other conditions and procedures, MedisGroups admission severity groups cannot fairly adjust for interhospital case mix differences in outcome studies.

Aged↗
PubMed1991

Prostaglandin E2 accelerates sexual behavior in male rats.

Sexual behavior in male rats is accompanied by an increase in body temperature of 18 degrees C. It has been suggested that this increase may be, at least in part, a febrile response mediated by the endogenous central release of prostaglandins of the E series (PGE). This putative release of PGE could also affect the expression of sexual behavior, a possibility that was tested in the present experiment. PGE2 was infused into the cerebral aqueduct and sexual behavior and hypothalamic temperature were monitored. PGE2 infusion raised hypothalamic temperature and decreased the postejaculatory interval and ejaculation latency. The exact cause of this acceleration of sexual behavior cannot as yet be determined.

Animals↗
PubMed1991

On the significance of similarities between ultrasonic vocalizations of infant and adult rats.

The communicatory significance of the 40 kHz vocalization of rat pups and the 22 kHz vocalization of adult rats have been topics of research for over three decades. The 40 kHz vocalization is emitted by pups during cold exposure, whereas the 22 kHz vocalization is emitted by adults following ejaculation, following defeat in aggressive encounters, as well as in other contexts. Recent research suggests that the 40 kHz vocalization is the acoustic by-product of a respiratory mechanism that enhances gas-exchange in the lungs during times of increased oxygen consumption. Furthermore, a reevaluation of research into the physiological basis of the 22 kHz vocalization suggests a similar conclusion. In the present paper, we discuss mechanistic and contextual aspects of ultrasound production. We conclude that these two vocalizations, produced by identical mechanisms and reflecting identical physiological states, are actually the same vocalization, albeit at different frequencies. This alternative view of ultrasound production has implications for our interpretation of the communicatory significance of these vocalizations.

Aging↗