Effect of maternal presence on the fear response to an unfamiliar environment as measured by heart rate in rats as a function of age

Rats 16 to 60 days of age were placed in an unfamiliar environment either alone or in the presence of an anesthetized lactating dam. Rats of all ages show a dramatic increase in fear, as measured by heart rate (HR), when placed alone in an unfamiliar environment. Adult rats, however, show a rapid decline in heart rate during the course of a 90-min session, whereas 16-day-old rats show no significant decrease in HR during the same period. These results suggest that the adult rats become less fearful of the test environment over time, but that the 16-day-olds maintain a high level of fear throughout the 90-min test period. Twenty-three- and 30-day-old rats show an adultlike pattern of adaptation to the unfamiliar environment, i.e., their heart rates return partially but not completely to baseline levels within the 90-min session. When an anesthetized lactating dam is present in the test environment, a strikingly different pattern of results is obtained. Heart rate in the 16-day-old rat is immediately reduced to near baseline levels whereas in the young adult (60-day-old) rat the presence of the anesthetized dam has no effect on either initial HR or rate of adaptation. Again the 23- and 30-day-old rats showed an intermediate pattern of adaptation. In two follow-up experiments the effects of adding (Expt. 2) or removing (Expt. 3) an anesthetized dam on the 16-day-old rats' response to an unfamiliar environment was examined. Both experiments showed that animals were more fearful when the dam was absent from the environment than when it was present.

Effects of home nest odors on black-white preference in the developing rat: implications for developmental learning research

Developing animals 17 and 30 days of age were tested for black-white preference in the presence of either clean shavings or soiled bedding material from the home cage. Home nest shavings markedly reduced dark preference in 17-day-old rats but had no effect on dark preference in 30-day-old rats. Because many developmental studies have used two-compartment, black and white chambers to study the effects of familiar home nest shavings on learning and memory, it may be that differential preference for black influenced the results obtained. The apparent alleviation of learning and memory deficits produced by the presence of home nest shavings may have been the result of changes in black-white preference rather than differences in learning and memory per se. Similar influences may underlie the effects of home nest stimuli on other learning tasks such as spatial alternation.

Effect of chronic undernutrition on susceptibility to cold stress in young adult and aged rats

Chronically undernourished laboratory rodents live as much as 50% longer than matched control animals fed ad libitum. In their natural habitats, however, most mammals, including humans, appear to have shorter life expectancies when chronically undernourished. The present research demonstrated that both brief and chronic undernutrition speeds rate of body temperature drop in rats exposed to cold air. Furthermore, chronic undernutrition also decreased the rate at which body temperature returned to normal after animals had been removed from the cold environment. These results suggest that while chronic undernutrition may slow the rate of physiological aging it also increases the organism's susceptibility to stressor stimuli.

Unfamiliar environments impair information processing as measured by behavioral and cardiac orienting responses to auditory stimuli in preweanling and adult rats

Placing animals in an unfamiliar environment triggers at least two major reactions: (1) a heightened state of arousal, fear, or distress and (2) a sharp increase in information processing as the animal attempts to learn about its new environment. These changes could have a profound effect on the way in which the animal reacts to the types of extraneous innocuous stimuli typically used to study learning and memory. For example, an increase in arousal or fear could either (1) make the animal more "attentive" to stimulus change resulting in a larger orienting response, or (2) produce a shift from orienting to defensive responding. Conversely, processing of the new stimuli present in the unfamiliar environment may make the animal less responsive to additional extrinsic stimulation. These possibilities were examined experimentally using both autonomic and behavioral measures of orienting and defensive responses. The results demonstrated that animals fail to exhibit either an orienting response or a defensive response to a novel auditory stimulus when they are first placed in an unfamiliar environment. With continued exposure to the test environment the orienting response appears and then shows a time-dependent increase in magnitude. This pattern of results was obtained in both preweaning and young adult rats. On the basis of additional research and analysis, it was concluded that a limitation in information processing capacity was the primary reason for the failure of the orienting response to occur when an animal is first placed in an unfamiliar test chamber.

Measuring attitudes of doctors: the doctor-patient (DP) rating

An attitude scale was devised to discriminate between the extremes of doctor-centred, disease-oriented as opposed to patient-centred, problem-oriented (the DP scale). Four groups of subjects (214 in all) were tested with a Likert-type questionnaire based on this scale. Significant differences in attitude between the groups were found. Educational implications are discussed.

Stimulus attributes of reactivated memory: alleviation of ontogenetic forgetting in rats is context specific

Numerous studies have shown that ontogenetic forgetting (infantile amensia) can be alleviated by a number of different types of reminder treatment. The present study extends the information about the alleviation of infantile amnesia by examining the "content" of the reactivated memory. Toward this purpose, one attribute of memory (environmental context) was examined in rats tested either shortly after training (preamnesic) or after 1-week retention interval. For the latter, a reactivation treatment was used to reverse infantile amnesia. At both intervals, a context shift resulted in impaired performance of a conditioned fear response. These findings demonstrate that environment context is an important component of the originally encoded memory as well as the reactivated amnestic memory. The implications of these results for both the reactivation of memory and general memory processes are discussed.

Abnormal orthostatic changes in blood pressure and heart rate in subjects with intact sympathetic nervous function: evidence for excessive venous pooling

The normal ranges of orthostatic changes in blood pressure and heart rate have been defined in 92 individuals aged 18 to 64 years. In 34 individuals whose symptoms (especially orthostatic light-headedness) suggested cerebral ischemia, but in whom none of the known causes of orthostatic hypotension could be identified, we have found one or more of five theoretically possible orthostatic circulatory derangements: systolic hypotension, diastolic hypotension, diastolic hypertension, excessive narrowing of the pulse pressure, and tachycardia after standing for at least 3 minutes. The orthostatic disorders of blood pressure and heart rate identified in the 34 patients were significantly reduced, almost always into the normal range, by external pressure of 45 to 50 mm Hg applied through an inflatable pressure suit. After labeling with sodium pertechnetate Tc 99m and reinjecting the erythrocytes contained in 3 to 6 ml blood, external gamma counting over a fixed site in the calf, both in the recumbent and in the standing posture, showed excessive gravitational pooling of blood in the legs of five patients with orthostatic diastolic hypertension, of four with orthostatic narrowing of the pulse pressure, and of 10 with orthostatic tachycardia alone. Plasma norepinephrine concentrations were usually normal in recumbency and elevated above normal limits during standing for 15 to 30 minutes in the 18 patients so observed. Red cell mass, plasma volume, and circulating blood volume were subnormal in more than half the seven patients in whom these measurements were made. We conclude that most of the patients with idiopathic sympathicotonic abnormalities of orthostatic blood pressure control have a venous pooling syndrome often aggravated by hypovolemia, the cause(s) of which remains to be determined.

Effects of chronic dietary restriction on sensory-motor function and susceptibility to stressor stimuli in the laboratory rat

Two sets of experiments describing the effects of chronic undernutrition on sensory-motor function and susceptibility to environmental stressors are described. In the first, Fischer 344 rats between 10 and 12 months of age were placed on an every-other-day feeding regimen. Behavioral tests designed to assess sensory function (auditory and visual thresholds), somato-motor competence (hang time from a horizontal wire, balance on a narrow beam, descent of a wire mesh pole), and sensory-motor integrity (auditory startle) were then conducted every 3 to 6 months. Chronic undernutrition significantly increased life span and increased somato-motor competence but did not affect sensory function or sensory-motor integrity. In the second set of experiments both acute and chronic dietary restriction impaired the ability of young adult Sprague-Dawley rats to effectively thermoregulate in response to a cold environment. Body temperature dropped more rapidly and recovered at a slower rate in the dietarily restricted animals. Fischer 344 rats maintained on a restricted diet for 16 months were similarly impaired. The latter findings suggest that techniques for extending life span based on laboratory animal models may have little relevance to either animals or humans living in their natural habitats where a wide variety of environmental stressors are encountered.

Pathogenesis of the impaired gall bladder contraction of coeliac disease

We have investigated the possibility that the abnormally decreased gall bladder contraction after meals in patients with coeliac disease might result in part from an abnormality in the gall bladder response to endogenous cholecystokinetic hormones--for example, cholecystokinin and motilin--rather than solely from decreased secretion of such hormones. Eight patients with untreated coeliac disease and nine controls received intravenous infusions of the pure synthetic cholecystokinin analogue caerulein, 2-16 ng/kg/hour. Gall bladder emptying was measured on a minute-by-minute basis using 99mTc-HIDA scans. In the patients with coeliac disease, gall bladder emptying was greatly decreased (34.6 +/- 9.9 v 61.5 +/- 7.5% at 60 minutes, p less than 0.02), and a much greater dose of caerulein was needed to initiate gall bladder contraction (3.80 +/- 1.08 v 1.49 +/- 0.56 ng/kg, p less than 0.02). These results suggest that the abnormal gall bladder contraction in coeliac disease is not simply because of impaired release of cholecystokinin. Although mechanical factors secondary to the increased gall bladder size in patients with coeliac disease might to some extent account for the findings, the alternative explanation is that the gall bladder muscle is for some reason resistant to the action of cholecystokinetic agents. A similar phenomenon affecting the pancreas might contribute to the abnormally decreased pancreatic secretion found in coeliac disease.

Differential susceptibility to anterograde and retrograde amnesia treatments in preweanling rats

Although there have been several reports that preweanling rats and mice are relatively resistant to experimentally induced retrograde amnesia, there is virtually no information concerning susceptibility to anterograde amnesia in subjects of this age. Therefore, in the present experiment, 23-day-old rats received hypothermia either prior to, or immediately after, punishment training in an attempt to induce anterograde and retrograde amnesia, respectively. When tested 24 hr later, only those subjects given hypothermia prior to training exhibited any loss of retention. Thus these results confirmed previous evidence of resistance to retrograde amnesia in preweanling rats and further demonstrated that substantial anterograde amnesia could be obtained in these subjects. Performance of subjects tested after a 5-min retention interval revealed that the poor retention performance in subjects cooled prior to training and tested 24 hr later was not due to a learning deficit. These results are also discussed with respect to the issue of the independence of anterograde and retrograde amnesia.

Jeremy Bentham's self image: an exemplary bequest for dissection

Images

Hypothermia-induced anterograde amnesia: is memory loss attributable to impaired acquisition?

The present investigation examined whether the poor test performance observed in studies of anterograde amnesia reflects a memory deficit or is a by-product of weaker initial learning resulting from impaired sensory, motivational, or associative processes. Two experiments were performed which utilized latent extinction (Experiment 1) and delay of punishment (Experiment 2) manipulations in order to assess the nature of original learning in rats trained under either hypothermic (29 degrees C) or normothermic conditions. Results from both experiments provided evidence that hypothermia treatment administered prior to training had relatively little influence on the animal's ability to acquire a passive avoidance response. Therefore, the rapid forgetting observed in hypothermia-induced anterograde amnesia is most likely due to memory deficits rather than an artifact of poorer acquisition.

A monoclonal antibody to a zona pellucida-proteinase inhibitor binding component on murine spermatozoa

A monoclonal antibody, J-23, was produced to an epitope of a binding (acceptor) component on the plasma membrane in the acrosomal cap region of the mouse sperm head. The component binds a proteinase inhibitor of seminal vesicle origin at ejaculation and participates in the in vitro binding of capacitated sperm to the zona pellucida. The antibody, an IgM molecule, recognizes affinity purified acceptor, crude acceptor and whole sperm as determined by ELISA methodology. The antibody reacts with a 15,000 molecular weight component, the size previously determined for the acceptor, found in the supernatants of frozen-thawed cauda epididymal sperm. In addition, it binds to a 21,000 molecular weight component generated by mixing an excess of purified inhibitor (6400 daltons) with a crude acceptor preparation. J-23 binds to an epitope in the same region of the sperm head as does the inhibitor. This epitope becomes fully expressed during epididymal maturation and is found only in the lumen of epididymal tissues. Pretreating sperm with J-23 inhibits their ability to bind the inhibitor as well as the zona pellucida. Pretreating sperm with the inhibitor has little effect on the binding of J-23. These data indicate that J-23 recognizes an epitope on the acceptor but the epitope is not directly involved with inhibitor binding.

Features of a seminal proteinase inhibitor- zona pellucida-binding component on murine spermatozoa

Murine cauda epididymal sperm contain sites on the plasma membrane over the apical portion of the acrosome that recognize proteinase inhibitors and the homologous zona pellucida. Ten times more of the component can be extracted from cauda and ductus sperm than from equal numbers of caput and corpus sperm. Likewise, few sperm from the upper epididymal regions are able to bind seminal inhibitor, while the majority of sperm from the cauda and ductus do bind. Cauda epididymal and ductus sperm lose little of their ability to bind inhibitor after a 4-hour in vitro incubation in either a capacitating or a noncapacitating medium. The percentage of naturally inseminated sperm with the seminal inhibitor bound to their surface decreases to about 10 after 4 hours in utero. Approximately 80% of these sperm show positive fluorescence when given the opportunity to rebind the the inhibitor, and these sperm do have an intact plasma membrane over the apical portion of the acrosome. Furthermore, after 4 hours in utero, the inhibitor bound in the same region of the sperm head as it did on freshly ejaculated sperm. The seminal inhibitor inhibits the binding of sperm to the zona if added during the first 15 minutes of incubation but has no effect on attachment. The data indicate that sperm gain the ability to bind the seminal inhibitor during the epididymal sojourn. Furthermore, this binding capacity is not lost during in vitro or in utero incubation. The site is not involved in sperm-zona attachment but does participate in the binding of sperm to the zona.

Differential susceptibility to anterograde and retrograde amnesia treatments in preweanling rats

Although there have been several reports that preweanling rats and mice are relatively resistant to experimentally induced retrograde amnesia, there is virtually no information concerning susceptibility to anterograde amnesia in subjects of this age. Therefore, in the present experiment, 23-day-old rats received hypothermia either prior to, or immediately after, punishment training in an attempt to induce anterograde and retrograde amnesia, respectively. When tested 24 hr later, only those subjects given hypothermia prior to training exhibited any loss of retention. Thus these results confirmed previous evidence of resistance to retrograde amnesia in preweanling rats and further demonstrated that substantial anterograde amnesia could be obtained in these subjects. Performance of subjects tested after a 5-min retention interval revealed that the poor retention performance in subjects cooled prior to training and tested 24 hr later was not due to a learning deficit. These results are also discussed with respect to the issue of the independence of anterograde and retrograde amnesia.

ACTH- and noncontingent footshock-induced recovery of an extinguished passive avoidance response

The effectiveness of both exogenous adrenocorticotropic hormone and noncontingent footshock as agents for the recovery of an extinguished passive avoidance response was assessed. Six groups of male Holtzman rats were administered either adrenocorticotropic hormone (4IU), or a single noncontingent footshock, either 15 minutes, 24 hours, or 7 days prior to retention testing. Two control groups received an injection of the inactive gel vehicle either 15 minutes or 7 days prior to test. Adrenocorticotropic hormone administered either 15 minutes or 24 hours prior to test, as well as noncontingent footshock delivered 24 hours (but not 15 minutes) prior to test, served as effective reinstatement agents. Substantial "spontaneous recovery" of responding precluded evaluation of reinstatement effects at the 7 day retention interval. The persistence of the recovery for at least 24 hours is consistent with the notion that both adrenocorticotropic hormone and noncontingent footshock not only enhance memory retrieval of the original fear conditioning, but also cause the training memory to be further processed.

Alleviation of infantile amnesia in rats by internal and external contextual cues

A previous study [Richardson, R., Riccio, D.C., and Jonke, T. (1983). Alleviation of infantile amnesia in rats by means of a pharmacological contextual state. Devel. Psychobiol., 16:511-518] found that ontogenetic forgetting ("infantile amnesia") in rats was attenuated by a "contextual matching" manipulation: Subjects trained in a distinct pharmacological state and tested in that state retained learned fear better than saline controls. To determine whether improved retention could be obtained with salient but nonpharmacological contexts, two experiments were conducted employing fear conditioning in preweanling rats. In Experiment 1, an internal context (illness induced by lithium chloride) present at training and testing reduced infantile forgetting. In Experiment 2, matching an exteroceptive context (home nest shavings) at training and testing was also found to be sufficient to alleviate infantile amnesia. In both experiments, retention was not improved in controls exposed to the context at training only or testing only, indicating that the contextual effect is not on acquisition or retrieval processes per se. These findings provide indirect support for views that emphasize the role of contextual cues in retrieval (Spear, 1978). In addition, they indicate that contextual matching is not limited to a state dependent drug, but may include a wide range of "distinctive" stimuli.

Total parenteral nutrition: a four-year audit

A four-year audit was carried out on 278 patients who received 289 courses of total parenteral nutrition (TPN) over 5213 patient days in a Saudi Arabian hospital. One hundred and forty-seven patients were discharged healthy, two of these after home TPN. The overall mortality was 36 per cent. ICU patients had the highest mortality (53 per cent). Among the survivors, 74.8 per cent showed an improvement in nutritional status. The incidences of metabolic complications and catheter sepsis were 2.9 per cent and 3.6 per cent, respectively. As a direct result of the audit, changes have been made in protocols and staffing patterns, and an attempt is being made to address the major problem of better selection of patients.

Administration of dexamethasone prior to training blocks ACTH-induced recovery of an extinguished avoidance response

Pretest administration of ACTH has been shown to produce recovery of an extinguished avoidance response. Presumably this effect is found because endogenous ACTH is a component of the original training memory. However, another possible explanation of this finding is that administration of the peptide acts as a novel stimulus that "disinhibits" the extinguished response. In order to test this "disinhibitory" hypothesis of ACTH-induced recovery of an extinguished avoidance response, some subjects were given dexamethasone 2 hr prior to training and extinction. This synthetic glucocorticoid is effective in blocking endogenous release of ACTH. Thus, ACTH should not be a component of the training memory in subjects given dexamethasone prior to training and extinction but would be a relatively novel stimulus condition at testing. Pretest administration of ACTH was found to be effective in alleviating performance deficits induced by extinction only for subjects given saline prior to training and extinction. Administration of ACTH had no effect on the avoidance responding of subjects given dexamethasone. These findings suggest that pretest administration of ACTH affects retrieval processes rather than acts as a disinhibitor.

Competition between seminal and exogenous proteinase inhibitors for sites on murine epididymal sperm

Sixteen proteinase inhibitors were tested for their ability to compete with the natural seminal inhibitor for binding to the surface of murine epididymal sperm. The most effective competitors, 4-methylumbelliferyl-p-quanidinobenzoate (MUGB) and p-nitrophenyl-p-guanidinobenzoate (NPGB), are also effective inhibitors of both murine acrosin and in vitro fertilization of mouse gametes. The data support the suggestion that the inhibition of fertilization by these inhibitors may be effected by their action on the sperm surface rather than binding to enzymes located within the acrosome. Since the surface acceptor molecule recognizes a number of inhibitor types, as well as substrates for such enzymes as trypsin and acrosin, the acceptor's binding site may be similar to the active site on the enzyme.

Administration of dexamethasone prior to training blocks ACTH-induced recovery of an extinguished avoidance response

Pretest administration of ACTH has been shown to produce recovery of an extinguished avoidance response. Presumably this effect is found because endogenous ACTH is a component of the original training memory. However, another possible explanation of this finding is that administration of the peptide acts as a novel stimulus that "disinhibits" the extinguished response. In order to test this "disinhibitory" hypothesis of ACTH-induced recovery of an extinguished avoidance response, some subjects were given dexamethasone 2 hr prior to training and extinction. This synthetic glucocorticoid is effective in blocking endogenous release of ACTH. Thus, ACTH should not be a component of the training memory in subjects given dexamethasone prior to training and extinction but would be a relatively novel stimulus condition at testing. Pretest administration of ACTH was found to be effective in alleviating performance deficits induced by extinction only for subjects given saline prior to training and extinction. Administration of ACTH had no effect on the avoidance responding of subjects given dexamethasone. These findings suggest that pretest administration of ACTH affects retrieval processes rather than acts as a disinhibitor.