Biomedical subjects
Publications and source records attributed to C B Clifford.
The author explains how to determine how many animals in a population need to be sampled when monitoring for pathogens. He concludes that even with perfect testing programs, there is always a chance that an infected animal will be missed.
Ringtail is a pathologic condition of the tail of rats and other rodents that is traditionally attributed to low environmental humidity, although dietary deficiencies, genetic susceptibility, environmental temperature, and degree of hydration of the animal also have been suggested as possible causes. To the authors' knowledge, a detailed histopathologic study that may serve to shed light on the etiopathogenesis of this disease has not yet been published. We describe the histologic findings of ringtail observed in 12 suckling Munich Wistar Fromter (MWF) rats from two litters. Epidermal hyperplasia characterized by orthokeratotic and parakeratotic hyperkeratosis and acanthosis was observed in all affected rats. Numerous often dilated vessels were present in the dermis of tails that appeared of red/brown color at gross examination. In severe cases, the dilated vascular structures were thrombotic and accompanied by dermal hemorrhages and focal coagulative necrosis of the overlying epidermis. These findings suggest that epidermal acanthosis and hyperkeratosis are the main and primary events in the development of ringtail. To clarify the cause of this disease, future studies should be focused on the numerous factors that can induce such epidermal changes.
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The purpose of this study was to characterize a spontaneous disease condition causing hyperkeratosis in nude mice and to explore the etiologic role of a particular species of coryneform bacteria in this disease, colloquially known as "scaly skin disease." The study was divided into two parts. In the first phase, a series of inoculation experiments was conducted with a field isolate of the coryneform species used to study the clinical and histopathologic development of the disease syndrome. Athymic nude mice (4 to 5 weeks old) were inoculated on the skin of the back with a suspension of a pure culture of the coryneform bacterium that had been isolated from a field case. The culture was applied with a sterile cotton swab in concentrations varying from 6.1 x 10(4)/ml to 5.0 x 10(7)/ml. All inoculated mice became persistently infected throughout the 33 days of the experiment. Clinically evident hyperkeratosis in inoculated animals developed more frequently in mice housed in a microisolator cage than in a semi-rigid isolator and more frequently in mice inoculated with higher numbers of organisms. In all animals in which hyperkeratosis developed, it was first noted on day 7 after inoculation. The second series of experiments was designed to determine the success of various housing methods in excluding the infection, mechanisms of transmission, susceptibility of other stocks and strains of mice to the organism, and whether the other strains might serve as a source of the organism. Results of the study in various strains indicated that both immunocompetent and immunodeficient mice, whether glabrous or hirsute, could be infected with the organism, but only glabrous animals developed hyperkeratosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Prehospital fluid resuscitation of traumatic injury is limited by difficulty in delivering large volumes of fluid in the field and time delays associated with gaining vascular access. We addressed these limitations in 14 anesthetized swine by evaluating a highly efficient volume expander, a near-saturated salt-dextran solution (SSD) administered through a new device, which gains vascular access via intraosseous (IO) infusion into the sternal bone marrow. After a steady-state baseline was achieved, all animals were hemorrhaged to 45 mm Hg for one hour. Half of the hemorrhaged animals were infused intraosseously with either normal saline (NS) or SSD until cardiac output was restored to the baseline value. No further infusion was given and animals were monitored for 2 hours. Both regimens were able to restore cardiac output to the baseline value, but only 1.3 +/- 0.1 mL/kg of SSD was required vs. 31.6 +/- 6.3 mL/kg for NS. In addition, cardiac output was better sustained after 2 hours with SSD than with NS. No deleterious effects of IO infusion of SSD were observed. From the improvement in cardiovascular variables and the lack of significant sternal or pulmonary pathologic perturbations, these data suggest that IO infusion of SSD can effectively treat hypovolemia and may allow field treatment when logistic considerations make conventional resuscitation impractical.
A 7.5% sodium chloride/6% Dextran solution (HSD) is effective for restoration of cardiovascular function after hemorrhagic shock. In the present experiments, we tested the usefulness and side effects of a 25% NaCl/24% Dextran solution (SSD), compared to HSD and 0.9% NaCl (NS). After 1 hr of baseline observation, 21 anesthetized pigs were submitted to hemorrhagic shock, maintaining a mean arterial pressure of 45 mmHg for 60 min. Continuous intravenous infusion of one of the solutions was then initiated and the infusion rate adjusted to restore and maintain cardiac output at baseline levels for 2 hr. The NS group required 121 +/- 22 ml/kg to achieve full resuscitation, while the HSD and SSD groups required 6.3 +/- 1.3 and 1.7 +/- 0.2 ml/kg, respectively. We conclude that SSD infusions were exceedingly effective at restoring cardiovascular function in volumes equal to only 10% of bled volume, but were associated with transient hemolysis and peripheral vein inflammation.
STUDY OBJECTIVES: With renewed interest in intraosseous (IO) infusion, the present study examined if sternal IO infusion provided vascular entry of 7.5% NaCl/6% dextran-70 (HSD) as efficiently as IV infusion. DESIGN, SETTING, TYPE OF PARTICIPANTS, INTERVENTIONS: Twelve anesthetized pigs were catheterized for measurement of cardiovascular parameters. Six pigs were given a 4-mL/kg IO infusion of HSD under pressure over two to six minutes; each pig was paired with another that had been given HSD IV over the same time course. Rapid arterial blood sampling was used to evaluate vascular entry of NaCl and dextran with monitoring continued for two hours after infusion. MEASUREMENTS AND MAIN RESULTS: Complete vascular entry of infused sodium and dextran was generally complete within one minute after infusion in all experiments. Increases in mean arterial pressure, cardiac output, and other cardiovascular parameters were indistinguishable between IO and IV infusions. Plasma volume expansion was about 20% above baseline in both groups of pigs. Histologic examination showed minimum pathology to the sternum and no significant pulmonary complications. CONCLUSION: 1O vascular delivery of HSD is a viable alternative in emergency scenarios in which vascular access is compromised.
Fluid percussion brain injury is associated with an immediate rise in mean arterial pressure (MAP). However, the cerebral morphologic basis for this response is still not clear. Thirty-four anesthetized rats were injured using a lateral craniotomy preparation. In 19 rats, impact level was set at 1.73 +/- 0.04 atm, and impact duration was kept at 25 msec to examine the relationship between postinjury hypertensive response and cerebral lesions. MAP was monitored for 1 hour after impact. Fluid percussion produced an increase in MAP from 99 +/- 3 to 134 +/- 4 mm Hg (p less than 0.001), with an increment range of -2 to 87 mm Hg (36 +/- 5 mm Hg) or 0 to 96% increase. The MAP peak occurred at 15 +/- 2 seconds and then rapidly returned to the preimpact level. Histopathological findings, principally hemorrhage, were graded and ranked from 1 to 19 according to relative severity and hypothalamic involvement. There was a significant correlation between MAP rise and the injury ranking (r = 0.52, p = 0.02). No appreciable damage was observed in the brainstem caudal to the diencephalon. Fifteen rats were subjected to higher injury levels. The overall impact magnitude ranged from 1.3 to 3.5 atm. A linear relationship was found between impact magnitude (X, atm) and increment in MAP (Y, mm Hg) (Y = 28.1*X - 14.0, r = 0.62, p less than 0.001). Our study indicates that the immediate postinjury hypertensive response is closely correlated with the impact magnitude and may be related to intracerebral hemorrhage and hypothalamic damage but not necessarily to caudal brainstem damage.
The effects of brain trauma on cardiovascular and endocrine responses to hemorrhage were investigated. Forty anesthetized rats were randomly assigned to one of four groups of 10 rats each: a control group (Group C): a group with induction of hemorrhage at 16.2 ml/kg/10 min (Group H); a group with fluid-percussion brain injury at a peak pressure of 1.7 atm and an impulse duration of 25 msec (Group T); and a group receiving hemorrhagic shock following brain trauma (Group TH). Group C and T rats showed no significant alterations in cardiovascular function. At the end of hemorrhage there were no significant differences between Groups TH and H in the nadirs of mean arterial blood pressure (MABP) (mean values +/- standard error of the mean: 42 +/- 2 vs. 40 +/- 4 mm Hg) and stroke volume index (SVI) (0.61 +/- 0.11 vs. 0.66 +/- 0.10 ml/bt/kg); however, 1 hour post-hemorrhage recovery was blunted in Group TH compared to Group H (MABP 56 +/- 4 vs. 65 +/- 3 mm Hg; cardiac index 182 +/- 15 vs. 220 +/- 15 ml/min/kg; and SVI 0.71 +/- 0.06 vs. 0.81 +/- 0.06 ml/bt/kg). Since the two groups showed no significant differences in heart rate, preload (central venous pressure), and afterload (systemic vascular resistance), the reduced cardiac index recovery in Group TH is believed due to the attenuation of cardiac contractile performance. The Group TH preparation potentiated hormonal responses to hemorrhage with significantly higher epinephrine and aldosterone levels than in Group H. Brain trauma enhanced the norepinephrine response to hemorrhage, even at an injury level that by itself did not result in an increase in this hormone. Group TH rats also had significantly lower blood pH and HCO3 levels. The data suggest that brain trauma suppresses MABP and cardiac index recovery after hemorrhage mainly by inhibiting cardiac contractile performance, probably due to high catecholamine levels and severe metabolic acidosis.
We developed a conscious pig model with a chronically instrumented kidney to measure renal blood flow (RBF), glomerular filtration rate (GFR), and excretory functions during hemorrhage. Seven to 10 days before experimentation, pigs were splenectomized, arterial and venous catheters were implanted, an ultrasonic flow probe was placed on the renal artery, and a pyelostomy was performed for nonocclusively placing a ureteral catheter. Measurements were taken before hemorrhage, and at hemorrhage volumes of 7, 14, 21, and 28 ml/kg (equivalent to 10.5, 21, 31, and 42% of the estimated blood volume), or at corresponding time points for controls. RBF was decreased by 30% when 21% of the blood (14 mg/kg) was removed, before arterial pressure, GFR, or urine flow or excretion was changed. At volumes of hemorrhage greater than 14 ml/kg, there were progressive decreases in RBF, GFR, urine flow rate, osmotic and electrolyte excretion, and arterial pressure. Thus pigs, like humans, respond to hypovolemia with an early redistribution of blood flow away from the kidney.
Hypervolemic infusion in rats of bis (3,5-dibromosalicyl) fumarate cross-linked hemoglobin (DBBF-Hb) to 40-60% of blood volume produced histologic lesions in retina which were not observed in rats similarly infused with human serum albumin or lactated Ringer's solution. Rats treated with 40% DBBF-Hb, exhibited intermittent zones of dense retinal pigmented epithelium while 60% DBBF-Hb animals exhibited severe inner retinal edema and retinal pigmented epithelium vacuolization, large focal zones of photoreceptor outer segment disruption and in one animal, subretinal hemorrhage. Light microscopic immunocytochemical evaluation of retinas with antibodies directed to human hemoglobin and albumin, showed the presence of both hemoglobin and albumin in this tissue. Transmission electron microscopy of the lesions demonstrated vacuolated retinal pigmented epithelial cells and large areas of focal photoreceptor outer segment disruption. We conclude that hypervolemic infusion disrupts the blood retinal barrier and that although both DBBF Hb and albumin cross, only hemoglobin produced damage in the retina.
Conscious rats were given either 14 g/dl bis(3,5-dibromosalicyl) fumarate cross-linked hemoglobin (DBBF-Hb) in lactated Ringer's (LR) as an intravenous bolus (40, 50, or 60% of blood volume), 12.5 g/dl human serum albumin (HSA) in LR as a control for oncotic effects, or LR as a control for injection volume. The high dose HSA and DBBF-Hb rats experienced pulmonary edema after injection; one rat in each of these groups died soon after dosing. Rats were killed after 48 hours for histopathology. Only the 60% HSA and the 50% and 60% DBBF-Hb rats had treatment-related lesions. In the liver, randomly distributed mononuclear cell aggregates occasionally surrounded a necrotic hepatocyte. Liver lesions in 60% DBBF-Hb rats were the largest and most numerous, but in all groups were qualitatively similar. Hearts from HSA and DBBF-Hb rats had similar mild inflammatory lesions. We conclude that bolus administration of DBBF-Hb causes morphologic lesions in rats only at volumes sufficient to cause pulmonary edema. Hepatic and cardiac changes with high volumes of DBBF-Hb resembled those in rats given a corresponding bolus of HSA, suggesting that vascular overload with a hyperoncotic solution, rather than cytotoxicity of DBBF-Hb, caused the injury.
Newborn calves, like human infants, are uniquely susceptible to bacterial infections. Part of this increased susceptibility may be related to defects in newborn polymorphonuclear leukocyte (PMN) defensive functions. It remains unclear whether reported deficits in newborn PMN function represent maturational disorders or are manifestations of some form of perinatal suppression phenomenon. We therefore compared the ability of bovine newborn PMNs (less than 24 h old), newborn PMNs (7-10 days of age), fetal PMNs (210-220 days gestational age), and adult PMNs to generate superoxide anion (O2-) as an indicator of respiratory burst activity. Citrated blood was collected, and PMNs were isolated to greater than 95% purity and 98% viability. O2- generation was measured as the superoxide dismutase-inhibitable (10 micrograms/ml) reduction of ferricytochrome c (2 mg/ml) after activation of PMNs with phorbol myristate acetate (PMA, 2 micrograms/ml) to directly stimulate protein kinase C. The reaction kinetics were measured (37 degrees C, 550 nm) using a spectrophotometer and chart recorder for continuous monitoring. O2- generation was measured for 5 min after the initial lag period and the total nanomoles of O2- generated calculated using the extinction coefficient for ferricytochrome c. Newborn PMNs (N = 10) generated significantly less O2- (5.7 +/- 0.8 nmol O2-/10(6) cells/5 min, P less than 0.01) than did adult PMNs (N = 14) (9.6 +/- 2.1 nmol O2-/10(6) cells/5 min) or fetal PMNs (N = 4) (10.7 +/- 0.7 nmol O2-/10(6) cells/5 min). PMNs from 7- to 10-day-old calves (N = 9) generated almost identical amounts of O2- as newborn PMNs (5.7 +/- 1.6 nmol O2-/10(6) cells/5 min). There was no difference in measured lag time period between newborn and adult PMNs, but fetal PMNs had significantly reduced (P less than 0.01) mean lag time. The data indicated that bovine newborn PMNs have a decreased ability to generate O2- in response to PMA stimulation, which persists for at least 7-10 days, and that this functional decrement may be a manifestation of some form of perinatal PMN suppression phenomenon rather than a developmental abnormality since fetal PMNs produced O2- as well as adult PMNs.
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The effects of the administration of methemoglobin (MetHb) prepared in vitro were evaluated in Sprague-Dawley rats given increasing doses of potassium cyanide (KCN). Median lethal dose (LD50) studies were conducted by giving intraperitoneal injections of KCN (in 0.3- to 0.5-ml volumes), then 2 min later administering intravenous (iv) doses of 1000, 1500, or 2500 mg/kg of MetHb through the tail vein. Control rats received an equivalent volume of saline. The resulting LD50 values for KCN were 7.4 +/- 1.1, 11.7 +/- 1.1, 13.9 +/- 1.0, and 14.2 +/- 1.0 mg/kg (mean +/- SD) for the control (no MetHb) and 1000-, 1500-, and 2500-mg/kg dose groups, respectively. Additional groups of rats were given 1000, 1500, or 2500 mg/kg MetHb and submitted for necropsy. The gross finding of darkened kidneys was present in both dose groups, but became consistent and more prominent in the 2500-mg/kg dose group. Evidence of pathologic changes was not present in other organs. Single-dose pharmacokinetic studies were conducted using iv doses of 1600 and 2500 mg/kg MetHb. The elimination half-life was similar in both doses (62.6 min), but the volume of distribution (95.3 +/- 7.2 and 126.3 +/- 5.2 ml/kg, mean +/- SE) and clearance (1.1 +/- 0.1 and 1.5 +/- 0.1 ml/min/kg) were significantly different (P less than 0.05) for the 1600- and 2500-mg/kg dose groups, respectively. From these data we conclude that although MetHb is cleared from the vascular system rapidly, it may be an effective and nontoxic antidote for doses of cyanide up to twice that of the control LD50.
Several in vitro functions of neonatal neutrophils (N-PMN) have been reported to be deficient and may be functionally related to the increased susceptibility of the newborn to infection. To evaluate an in vitro event corresponding to one of the early steps in the sequence of inflammation, we used zymosan-activated plasma as a source of activated complement fragments (Cf) and measured adherence of normal and Cf-stimulated bovine N-PMN to columns of Sephadex G-25. Adherence of control N-PMN and adult PMN (A-PMN) was comparable. When N-PMN and A-PMN were stimulated with a subaggregating dose of Cf, both responded with similar increases in adhesiveness. The stimulatory effect of Cf on N-PMN adhesiveness could be inhibited by pre-incubation of the N-PMN with either steroidal (0.05 mM dexamethasone) or non-steroidal (32 mM phenylbutazone) anti-inflammatory drugs. Ultrastructural observations correlated well with the results of the adhesiveness assays, and morphometric evaluation revealed an increase in the sectional circumference of Cf-stimulated N-PMN. Control cells were round with few short cytoplasmic projections, whereas Cf-stimulated cells exhibited marked shape irregularity, polarity, and prominent organelle-free lamellipodia development. There was a highly significant (P less than 0.001) increase in the measured circumference of Cf-stimulated cells. Thus, N-PMN were highly responsive to Cf stimulation, developed morphologic and functional changes indistinguishable from Cf-stimulated A-PMN, and were sensitive to pharmacologic inhibition.
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