Biomedical subjects
Publications and source records attributed to R Richardson.
Retroperitoneal vascular injuries are among the greatest challenges that confront the surgeon. Problems in resuscitation, exposure, and repair are numerous. Techniques to improve such perioperative tactics result in improved survival.
Six patients with acute peritonitis undergoing continuous ambulatory peritoneal dialysis for end-stage renal failure received an 800 mg loading dose of pefloxacin mesylate orally followed by 400 mg twice daily orally for 10 or 21 days. Plasma and dialysate levels of both pefloxacin and its metabolites were measured. Plasma levels in excess of the MIC for all infective bacteria were achieved within 90 min and in dialysate within 4 h. No significant accumulation of pefloxacin or its metabolite norfloxacin was noted. However, both serum and dialysate levels of the metabolite pefloxacin N-oxide rose continuously during treatment. Plasma and dialysate levels of all three agents fell rapidly during the five days after treatment had stopped. No major side effects were observed, although two patients developed Achilles tendonitis.
The socio-demographic and biological processes contributing to infant mortality and undernourishment were studied in five urban squatter settlements of Karachi. All those families who had experienced an infant death in the past 2 years (N = 106) were recruited into the study. Comparative children were selected by random numbers with geographical matching from families with at least one live infant and without a history of infant deaths in the past 2 years. The comparison children were weighed and those found underweight (27 per cent) were studied for the presence of risk factors. Forty-one per cent of all deaths were in the neonatal period, and in 47 per cent of cases deaths had occurred in infants with a birth order of 5 and above. Age, duration of breast feeding, birth interval, and the live/dead status of the previous sibling were significant biological variables accounting for 23 per cent of the variance for survival. Socio-economic status accounted for 22 per cent of the variance and health-seeking behaviour (antenatal care, immunization, etc.) for 28 per cent. Sixty-eight per cent of those underweight were more than 6 months old. Age, female sex, birth interval less than 24 months, duration of breast feeding, adolescent mother, alive/dead status of the previous child were significant influences accounting for 12 per cent of the variance. Socio-economic status and health seeking behaviour were also important determinants, but not to the same extent as in the case of infant death.
Previous research has shown that placement of preweanling rats in an unfamiliar environment inhibits both heart rate and behavioral orienting responses to an auditory stimulus, and that the orienting response gradually reappears during the following 15 min. Four experiments designed to evaluate two potential explanations of this effect were conducted. If the arousal induced by an unfamiliar environment disrupts sensory information processing, so should the arousal induced by mild electric shock. In two experiments, the orienting response was inhibited in proportion to number of shocks received and rate of recovery was comparable to that observed in the unfamiliar environment. New environments also contain many unfamiliar stimuli which may overload the rats' limited information processing capacity. In two experiments a change in environmental stimulation was shown to inhibit the orienting response. Recovery of the orienting response followed the same time course as that seen following shock or placement in an unfamiliar environment. Although the results of this study clearly demonstrate environmental inhibition of the orienting response, they provide little support for either the "arousal" or the "information overload" hypotheses of orienting response inhibition. The implications of these data for current theoretical conceptualizations of the orienting response are discussed.
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In two experiments the effects of the presence of an anesthetized lactating dam on the developing rat's response to a series of mildly painful shocks was examined. Both cardiac and behavioral responses to the shock stimulus were recorded. In the first experiment animals were tested at either 16, 20, or 24 days of age. The presence of the anesthetized dam markedly reduced the behavioral response to shock of the 16-day-old but not the older rats. A similar pattern of results was obtained with the shock-elicited tachycardia. The second experiment replicated these results with the 16-day-old rat and also demonstrated that being shocked in the presence of a lactating dam influences the animal's reaction to a subsequent series of shocks given when it is alone. The results of these two experiments are discussed in terms of other studies that have examined the influence of maternal presence on the developing animal's response to stressful or painful stimuli.
Murine cauda epididymal sperm possess a site, the acceptor, on the plasma membrane over the apical cap region of the acrosome which recognizes both a proteinase inhibitor of seminal vesicle origin and homologous zonae. The acceptor site may participate in both capacitation and zona binding. This presentation explores the effect of in vitro incubation in a medium known to induce capacitation on the binding capabilities of this site. Approximately 80% of fresh cauda epididymal sperm will bind the seminal inhibitor in vitro. Incubating sperm, pretreated with inhibitor for 2 hr in a medium (M199-M) known to support capacitation, reduces by 60% the number of sperm showing evidence of the inhibitor. No such decrease is seen when sperm are incubated in a medium (M199) that does not support capacitation. During the 2-hr incubation in either medium, 60-70% of the sperm retain two diverse components on the plasma membrane over the acrosome: a receptor for the Fc portion of IgG and an epitope recognized by a monoclonal antibody to the acceptor site. These observations suggest that the plasma membrane in the acrosome region of the cell remains structurally intact during incubation. Furthermore, sperm retain the ability to bind the seminal inhibitor during incubation. After a 2-hr incubation in M199-M, sperm pretreated with heat-solubilized zonae no longer bind the inhibitor. These sperm, however, retain the plasma membrane over the acrosomal cap region. When the sperm are incubated in M199, no decrease in inhibitor binding due to zona treatment is noted.(ABSTRACT TRUNCATED AT 250 WORDS)
Cervical teratomas in the newborn are uncommon and difficult management problems, as their natural history and prognosis are not well defined. Existing or potential airway obstruction is usually the main concern in acute management of these patients. Total excision is essential to avoid local recurrence in benign lesions, and a small but present risk of malignancy can result in death from metastatic lesions which appear later. A unique case of neonatal malignant cervical teratoma with large congenital metastatic lesions present in liver, lung, and buttocks was successfully managed. Magnetic resonance imaging (MRI) was invaluable, both in delineating these lesions and in planning a four-stage curative resection of all macroscopic disease. Such a case has not been reported previously.
Recent data suggest that ACTH administration produces recovery of an extinguished passive avoidance response at an unusually long injection-to-test interval. The present experiment sought to explore further the durability of recovery by examining the effect of ACTH following extinction of one-way active avoidance. Adult rats were injected with 16 IU ACTH, an equivalent volume of the ACTH vehicle gel, or saline 48 h after a previously learned active avoidance response was partially extinguished. Different groups from each treatment condition were tested 15 min, 24 h, or 7 days after injection. ACTH improved avoidance performance at all injection-to-test intervals relative to saline and vehicle gel injected controls. These data indicate that unlike reversal of other types of performance decrements, in which the effect of ACTH appears to be transient, administration of the hormone following an extinction treatment can produce enduring improvement of avoidance performance.
The material tensile strength of a range of convex-faced tablets, compacted under controlled conditions at pressures of 40 and 320 MPa from a size fraction of acetylsalicylic acid, has been assessed. The calculation of the tensile strength sigma 1, from observed fracture loads obtained in diametral compression testing, is based on the equation derived by Pitt et al (1988), namely: (formula; see text) where P is the fracture load, D is the tablet diameter, t is the overall tablet thickness and W is the central cylinder thickness. The strength of a tablet of a given shape compacted at 320 MPa was between two and four times greater than that of a similar tablet compacted at 40 MPa. For the thicker tablets (W/D greater than or equal to 0.2) the material tensile strength was practically independent of shape. For the thinner tablets (W/D = 0.1) the material tensile strength varied considerably with face-curvature, showing a maximum for each of the two compaction pressures at a D/R value of 0.67.
The trial was designed as an investigation into the incidence of both immediate and delayed reactions to the intravenous administration of Conray 325 (sodium iothalamate) (844 patients) and Niopam 300 (iopamidol) (855 patients) for urographic examination. Information was obtained from questionnaires returned by patients about a week after their examination, with a response rate of 81%. Significant differences were found in the incidences of both types of reactions to the two media with respect to nausea and vomiting, arm pain, and taste in the mouth, which was commoner in patients receiving Conray 325, whereas the incidence of delayed skin rashes and parotid swelling was commoner with Niopam 300. The occurrence of a flu-like illness, so-called "iodism", was found to be equal for the two contrast media.
Advancing age is associated with a markedly increased risk of suicide. In the United States, one fourth of all suicides are carried out by citizens age 60 or older. The majority of American elders who commit suicide use a firearm to do so. Most suicidal elders look to their primary care physician for help, although they may not directly express their plan. Therefore, physicians must be alert to clues. By far the principal risk factor for suicide is major depression. The risk is heightened by recent losses, alcohol or drug abuse, psychosis, cognitive decline, and chronic disease. Hopelessness, anhedonia, self-reproach, guilt, and a formed lethal plan are signs of a life-threatening suicidal crisis which requires urgent intervention. Physicians must act decisively in recognition of the fact that suicidality is a transient, treatable condition.
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.
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.
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.