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Biomedical subjects

R Silver

Publications and source records attributed to R Silver.

At least 109 records · Page 6Linked to original sources
PubMed1985

Associative factors and the development of pecking in the ring dove.

In these studies, descriptive information on the diet and feeding behavior of ring dove squab is considered in the context of an analysis of the mechanisms underlying the development of eating. Experiment I shows that squab begin to peck at grain around Day 13 and both the rate and efficiency of pecking increase through Day 21 when the squab are weaned. Experiment II shows that squab reared without seed in their home cage do not develop normal levels of pecking unless exposure to seed is followed in close temporal proximity by interaction with parents. It is concluded that an association between some aspect of squab's interaction with seed and a parentally provided unconditioned stimulus is sufficient for normal pecking to develop. The nature of these associations and their contribution to the ontogeny of independent feeding are discussed.

Animals↗
PubMed1985

Stimulus requirements for prolactin and LH secretion in incubating ring doves.

To study the regulation of prolactin secretion and incubation behavior during breeding, stimuli available during the prehatching period were manipulated, and plasma prolactin and LH and pituitary prolactin concentrations were assayed. Four groups were compared: (a) nest and eggs removed (b) eggs replaced with infertile eggs, (c) eggs replaced with infertile eggs and partners separated, and (d) unmanipulated controls. The increase in prolactin secretion that normally occurs at the end of incubation was reversed when the nest and eggs were removed but was unaffected by the absence of the mate. Prolactin secretion was not maintained in males sitting beyond the normal incubation period (on infertile eggs), while it was maintained in females but only in the presence of the mate. In the control birds, the increase in plasma prolactin was accompanied by an increase in pituitary content; while in the manipulated groups, an inhibition of prolactin secretion was associated with a transient increase in pituitary content. Plasma LH levels were low in control birds during the time of high prolactin secretion, and in all groups where the disruption of normal breeding stimuli caused an early fall in prolactin, there was a concomitant increase in LH secretion. In animals which had been separated from their mates and provided with a nest bowl and eggs, continuous observations of incubation behavior were made and plasma was sampled every third day. Parallel changes in prolactin and sitting behavior occurred in some of the animals, while others continued to incubate after prolactin had declined. In no instance did an animal which maintained high prolactin show a decline in incubation. This suggests that prolactin can serve to maintain incubation, while incubation does not necessarily stimulate prolactin secretion at this phase of the breeding cycle.

Animals↗
PubMed1985

Phase I-II trial of mitoxantrone in acute leukemia.

Mitoxantrone was evaluated in a multi-institution trial to define the effective dose for treating acute leukemia, to evaluate its toxicity, and to assess the induction rates for the different types of acute leukemia. Fifty-seven patients have been treated. Of the 24 patients receiving mitoxantrone (10 mg/m2/day X 5), one of nine with acute nonlymphoblastic leukemia (ANLL) in relapse, one of five with acute lymphoblastic leukemia in relapse, and one of seven with blastic chronic myelogenous leukemia achieved remission. At a dose of 12 mg/m2/day X 5, seven of 16 patients with ANLL in relapse, none of six with acute lymphoblastic leukemia in relapse, and one of five with blastic chronic myelogenous leukemia achieved remission. At both dose levels, there was no response in patients who had failed to achieve a prior remission. Toxic effects included nausea/vomiting, stomatitis, and hepatic dysfunction. Nine of the 57 patients treated experienced cardiac events but cardiac toxicity seemed clinically significant in only three. We conclude that mitoxantrone, at a dose of 12 mg/m2/day X 5, is effective therapy for ANLL. Trials combining mitoxantrone with other agents are needed.

Acute Disease↗
PubMed1985

Anticentromere antibody and immunoglobulin allotypes in scleroderma.

Fifty-five unrelated whites with disorders in the scleroderma spectrum who had both antinuclear antibodies and Raynaud's phenomenon (RP) were studied. Of the 22 patients with anticentromere antibody (ACA), three had diffuse scleroderma; 16 had the complete or incomplete syndrome of calcinosis, RP, esophageal dysmotility, sclerodactyly, and telangiectasia (CREST syndrome); and three had RP only. Thirty-three patients with other nuclear patterns all had systemic scleroderma (28 diffuse scleroderma, five CREST syndrome). Patients with ACA had less organ system involvement, and lower frequencies of anemia and elevation of sedimentation rate than ACA-negative patients, but these differences were not statistically significant. They also had fewer manifestations of CREST syndrome. All 55 patients were studied for the Gm and Km allotypic markers. No association was found between Gm or Km allotypic markers and scleroderma or between the allotypic markers and the presence of ACA.

Adolescent↗
PubMed1984

Placenta previa: aggressive expectant management.

We report the outcomes of 95 expectantly managed cases of placenta previa; all were diagnosed after 21 weeks' gestation. Patients at risk for preterm delivery because of hemorrhage or preterm labor received aggressive care, including multiple transfusions, volume expansion and tocolytic therapy, and amniotic fluid surfactant determinations, to achieve the goal of delivery at 37 weeks' gestation with mature fetal lung function. We present guidelines for outpatient management and double setup examination prior to delivery. The role of ultrasound in diagnosis (three asymptomatic cases; 13 cases with preterm labor) and serial placental localization to determine the timing, route, and place of delivery is presented. Eighty-six percent of 19 infants born weighing less than 2500 gm were managed expectantly. Hemorrhage was the determinant in delivery timing in 50 cases. All four deaths were neonatal with birth weights less than 2200 gm. This is the lowest perinatal mortality rate (4.2%) published to date. Use of this aggressive approach is particularly suitable for patients cared for in a teritary center.

Adolescent↗
PubMed1984

Prolactin and parenting in the pigeon family.

The relationship between plasma prolactin and: crop growth; incubation; brooding; and feeding young in Columbiformes is reviewed. There is a good parallel between changes in crop growth and plasma prolactin fluctuations during the breeding cycle. Prolactin does not play a role in the initiation of incubation, though it can maintain the response. Toward the end of breeding, a decline in prolactin precedes the decline in incubation (of infertile eggs) or brooding (of young), while exogenously administered prolactin can prolong the response. There is no evidence of a necessary relationship between prolactin secretion and parental feeding of young, as this behavior can precede and outlast the secretion of the hormone during breeding.

Animals↗
PubMed1984

Splitting of the circadian rhythm of body temperature in the golden hamster.

The circadian rhythm of hamster locomotor activity "splits" into two distinct circadian components during conditions of constant illumination. To determine if the circadian rhythm of body temperature also splits under these conditions, body temperature and locomotor activity were monitored concurrently in animals housed in constant illumination. Splitting of the body temperature rhythm into two circadian components was observed in animals manifesting split activity rhythms. Concurrent splitting of both rhythms suggests a common mechanism either for the generation or coupling of these rhythms.

Animals↗
PubMed1984

Two kinds of timing in circadian incubation rhythm of ring doves.

Ring dove males share incubation with females by sitting on the nest for a block of time in the middle of the day. The timing of nest exchanges was studied by experimentally delaying the onset, in the morning, of the male's sitting bout. Such delays induced a concomitant but smaller delay in the offset of the male's sitting bout in the afternoon. The female, however, approached the nest to start her bout of sitting at the usual time in the afternoon even though her previous sitting bout had ended later than usual. These findings, together with data on interactions between the pair at the afternoon exchange, suggest that the behavior of the sitting male reflects an interval timing mechanism initiated with the onset of his sitting bout. In contrast the attempts to regain the nest by the nonsitting female probably reflect a circadian oscillation.

Animals↗
PubMed1983

Geographical variation in mortality from conditions amenable to medical intervention in England and Wales.

There is a need for indicators of the outcome of health-care services against which the use of resources can be evaluated. From a previously published series of outcome indicators, which included diseases for which mortality is largely avoidable given appropriate medical intervention, causes were selected which were regarded as most amenable to medical intervention (excluding conditions whose control depends mainly on prevention) and for which there were sufficient numbers of deaths to allow an analysis of the variation in mortality rates among the 98 area health authorities of England and Wales. Considerable variation between AHAs was found in mortality from most of these diseases, and this variation remained even after adjustment for social factors. This substantial variation should be examined further in relation to health-service inputs and other factors. A finding of large variations in the quality of health-care delivery in different parts of the country would have important implications for resource allocation.

Adolescent↗
PubMed1983

Retinohypothalamic pathway in the dove demonstrated by anterograde HRP.

The hypothalamic suprachiasmatic nucleus (SCN) of the ring dove was demonstrated by the presence of labeled retinal processes. Horseradish peroxidase or tritiated proline were injected into the vitreous of the eye and were transported in an anterograde manner to label the SCN. After identifying the retinorecipient area of the hypothalamus by anterograde tracing procedures, a diffusely organized nucleus corresponding to this region was noted in Nissl material.

Animals↗
PubMed1983

Erythropoietin in liver tissue extracts and in liver perfusates from hypoxic rats.

An attempt to evaluate the role of the liver in extrarenal erythropoietin production was made by measuring the content of erythropoietin in homogenates and perfusates from hypoxic rat livers. Extracts from livers from nephric or anephric animals rendered both anemic and hypoxic showed no detectable erythropoietin despite the fact that both plasma and kidney extracts contained large amounts of erythropoietin. This lack of measurable erythropoietin in the liver is not caused by degradation of erythropoietin during the extraction procedure because exogenously added rat erythropoietin was recovered to the same extent from livers or kidney homogenates. More likely, however, it is caused by the fact that extrarenal erythropoietin production accounts for only one-fifth of total erythropoietin production and that the liver mass is about six times that of both kidneys. Consequently, the erythropoietin content of 1 g of liver should be about one-thirtieth of that of 1 g of kidney, an amount that is below the limit of detection of the assay. On the other hand, the 2-h in situ perfusates of livers from similarly stimulated animals contained significant amounts of secreted erythropoietin. It is concluded that the liver participates actively in extrarenal erythropoietin production in the adult rat. However, the small amount expected to be present in tissue homogenates cannot be detected with our current bioassay.

Anemia↗
PubMed1983

Assessment of coagulation cascade during air microembolization of the lung.

Experiments were performed to determine whether activation of the coagulation cascade was required for pulmonary vascular permeability to increase during microembolization of the lung. For 30-45 min air microemboli were intravenously infused (0.05-0.10 ml X kg-1 X min-1) into awake sheep with chronic lung-lymph fistulas and anesthetized mongrel dogs. During embolization the pulmonary arterial pressure increased, and O2 partial pressure (PaO2) fell by more than 20 Torr (P less than 0.01). Subsequently lymph flow nearly tripled without a change in the lymph-to-plasma protein concentration ratio. Partial thromboplastin and prothrombin times, biological activity of antithrombin III, and circulating concentration of 125I-labeled dog or sheep fibrinogen did not change during or following air infusion. In two additional sheep an intravenous infusion of thrombin at 0.6 U X kg-1 X min-1 for 15 min resulted in a 20% decrease in 125I-labeled sheep fibrinogen concentration without a change in pulmonary arterial pressure or PaO2. We conclude that air microembolization can increase permeability to water and protein without a detectable activation of the coagulation cascade in the sheep or dog.

Animals↗
PubMed1983

Timing of incubation bouts by ring doves (Streptopelia risoria).

Ring dove parents share in incubation and brooding such that the male sits for a block of time toward the middle of the day and the female sits the rest of the time. In order to evaluate the role of the sexes in determining nest exchange, approaches to the nest, the timing of incubation behavior, and the topography of interactions at the nest site were continuously monitored. Most nest exchanges (87%) were initiated by the nonsitting mate. There was less variability associated with the onset of sitting by the female than by the male. The male entered the nest area repeatedly from the time of lights-on until nest exchange several hours later. In contrast, the female rarely entered the nest area when the male was sitting, and when she did approach, nest exchange usually ensued. When the male's entrances to the nest area were prevented until the usual time of nest exchange, the timing of the subsequent sitting bout and nest exchange was not altered, which indicates that male visits are not a necessary prerequisite for nest exchange. Each pair developed a cooperative interaction as incubation progressed. When mates were exchanged among physiologically synchronized pairs, a serious disruption of sitting resulted. It is concluded that behavioral synchrony between the mates in the form of each pair's bond is as necessary as physiological synchrony in maintaining intermate cooperation in parental behavior of ring doves.

Animals↗
PubMed1983

Rotator cuff tear. Diagnosis and treatment.

Early surgical repair of rotator cuff tears with a partial anterior acromionectomy is recommended as a means of minimizing a progression of symptoms and findings. It was more important to achieve adequate tension in the cuff tissues than to obtain a water-tight closure. Even patients with old complete tears may obtain good results from reconstruction of the rotator cuff. However, merely closing a rotator cuff tear will not permit a good functional result if the ability of the muscles to contract adequately is lost forever. This group of patients rarely achieves full restoration of muscle strength in their operated shoulders, primarily due to muscle atrophy. In shoulders previously operated on, functional results were not as good as in those cases operated on for the first time. Avoidance of interposed soft tissue grafts and restoration of a direct continuity of viable rotator cuff tissue to its bony insertion are recommended whenever possible, to achieve the optimum functional result. In those patients with arthritis of the glenohumeral joint or permanent long-standing nonfunctional rotator cuff muscle, the results of reconstruction were poor. A carefully supervised postoperative rehabilitation program is essential for optimum results.

Acromion↗
PubMed1982

The effect of a low-phosphate diet on hematocrit and oxygen transport in uremic rats.

Dietary restriction of phosphate was found to prevent the development of anemia in partially nephrectomized rats. In an attempt to examine the reason for this beneficial effect, hematologic and nephrologic studies were carried out on normal and on partially nephrectomized rats fed either a normal or a low-phosphate diet. It was first found that a low-phosphate diet ameliorates the degree of renal impairment found four weeks after partial nephrectomy. Nevertheless, it did not eliminate it, and the degree of uremia actually observed should have been associated with a significant reduction in hemoglobin and red cell mass. However, it did reduce serum phosphate and red cell 2,3-diphosphoglycerate (2,3 DPG) levels and increase hemoglobin affinity for oxygen to a degree that should impair oxygen transport to the tissues. That the low phosphate actually caused tissue hypoxia with increased stimulation of the bone marrow was furthermore suggested by the observation that normal rats fed a low-phosphorous diet developed a significant increase above normal in hemoglobin concentration and red cell mass. It was concluded that the effect of a low-phosphate diet on the anemia of uremia is caused by a combination of reduced renal failure and increased tissue hypoxia.

Animals↗
PubMed1982

A comparison of Vitrathene moulded with Tweeklon ready-made wrist work splints in juvenile chronic arthritis.

A comparatiave study of purpose-made Vitrathene with a ready-made Tweeklon splint has been undertaken in 20 children with juvenile chronic arthritis who had such severe wrist and carpal involvement that a work splint was considered desirable. In half the dominant hand was splinted with Vitrathene and the other half Tweeklon. Assessments included the presence of soft-tissue swelling, extensor tenosynovitis and pain, together with the position and range of movement of the wrist, grip strength and functional tests. Tests included: maintenance of functional position, grip strength, dexterity, wear-resistance, and weight. Although the Vitrathene splint appeared better in the study, it was made by an experienced occupational therapist. The Tweeklon was applied by a physiotherapist reading the instructions which accompanied it; this took about a quarter of the time required to make the Vitrathene splints.

Adolescent↗