The meaning of risk assessment

For mst chemicals, human risk assessment begins when a significant number of cancers appear in a bioassay in which animals are exposed to the chemical in question. The assumption is made that any substance capable of causing cancer in animals can also cause cancer in humans. However, this attitude, as far as risk assessment is concerned, may become modified by estimates of sensitivity to carcinogenesis for animals versus humans, by the significance of animal tumor types and, possibly, by the development of an operational definition of a threshold. Risk/benefit considerations are appropriate but rest on scanty data. For the present, models for the prediction of human cancer following exposure to known animal carcinogens must be conservative and based on a zero threshold.

Acute appendicitis during pregnancy

From this study, we note: (1) misdiagnosis of appendicitis in pregnancy is comparable to that of the general female population; (2) with a maternal mortality of zero per cent, the operation is safe even when complicated by perforation; (3) fetal mortality is minimal; (4) clinical judgement rather than laboratory data must be relied on for diagnosis; and (5) the pregnant patient presenting with abdominal pain should be assessed and treated as one would any patient with the same complaint. The general use of this principle may explain the marked improvement in maternal and fetal mortality and morbidity in recent years.

Urinothorax following blunt trauma to the kidney

A case of urinothorax is reported in a 19-year-old girl with multiple injuries sustained in an auto accident. Thus blung injury to the right kidney was followed 8 days later by reduced urinary output and serous chest tube drainage. Intravenous dye injection showed dye in urine and in chest tube fluid, and the macerated right kidney was removed. The right pleural effusion then cleared with further drainage. The mechanism by which urine is transferred across the intact diaphragm is thought to be lymphatic drainage.

Increased survival with new techniques in treatment of gastroschisis

Since the opening of the Neonatology Unit, we have become the referral center for our area for problems in the newborn. In the past three years, we have treated five full-term and two premature infants with gastroschisis. There was one death in a premature infant. With an aggressive therapeutic approach and a new surgical technique, we have achieved an overall survival rate of greater than 85%. Primary closure was possible in three patients, with the remaining four being trreated in two stages. A modification of the Schuster silastic bag closure was first accomplished in those patients treated in two stages. Definitive surgical correction was completed within eight days of birgh in all seven patients. No ventral hernias or wound infections occurred using the new technique. Careful preoperative transport and management, judicious anesthesia, antibiotics, ventilatory support, and parenteral hyperalimentation when necessary, have all contributed to our increased survival rate and decreased morbidity.

Resistance to arteriosclerosis in pigs with von Willebrand's disease. Spontaneous and high cholesterol diet-induced arteriosclerosis

The aortas of 11 pigs (aged 1-3 yr) with homozygous von Willebrand's disease (vWd) were compared with those of 11 normal pigs of the same ages. Six of the controls exhibited multiple arteriosclerotic plaques with intimal thickening of 63-130 mum. In contrast, none of the pigs with vWd had multiple plaques, and only one had a lesion >2 mm in diameter. In a subsequent study, 3-mo-old pigs (11 controls and 7 with homozygous vWd) were placed on a 2% cholesterol diet for up to 6 mo. All of the controls developed arteriosclerotic plaques in the aorta, and in nine of the controls, at least 13% of the entire surface was involved. Intimal thickness ranged up to 390 mum. In contrast, four of the pigs with vWd did not develop such lesions, two developed arteriosclerotic lesions affecting 6 and 7% of the aortic surface, and the seventh had 13% of the aortic surface involved. Most of the pigs with vWd, however, developed flat fatty lesions in contrast to the normal pigs whether on the normal or the high cholesterol diet. There was blue staining of the flat fatty lesions when two pigs with vWd were injected with Evans blue dye antemortem. By electron microscopy, severe endothelial damage was apparent, but there was no intimal proliferation. The coincidence of the impaired platelet-arterial wall interaction and lack of arteriosclerosis in this bleeding disease is discussed.

Penetration of the small intestinal mucosa by asbestos fibers

Amosite asbestos fibers suspended in saline were placed in an isolated segment of rat jejunum in vivo. One hour later, segments of jejunal mucosa were taken for examination in three of the five rats exposed to the amosite suspension. Fibers also were presented in the lamina propria.

The significance of intraoperative ventricular fibrillation during aortic valve replacement

The effect of the spontaneous occurrence of ventricular fibrillation during aortic valve replacement and coronary arterial perfusion was studied in a consecutive series of 361 such operations. All operations were performed in a standard manner before 1972. One fourth of the patients experienced ventricular fibrillation,and the early mortality rate of this group was significantly (p less than 0.005) higher 7.3 per cent) than in the nonfibrillating group (1.5 per cent). The total mortality rate was 3 per cent. However, late results among survivors of the operations showed no effect of fibrillation. These findings indicate that ventricular fibrillation should be avoided in these patients. Whether or not countershock is advisable if and when fibrillation occurs remains an unanswered question.

Quantitation of left ventricular myocardial fiber hypertrophy and interstitial tissue in human hearts with chronically increased volume and pressure overload

Using new techniques, we quantitated left ventricular myocardial fiber hypertrophy and interstitial tissue in four groups of autopsied hearts free of coronary disease: 1) 22 normal hearts, 2) 20 hearts from patients with mitral incompetence (NYHA Class II-III) who died early after mitral valve replacement from causes other than cardiac failure, 3) 22 hearts from patients with mitral incompetence (NYHA Class III-IV) who died early after mitral valve replacement from cardiac failure with low cardiac output syndrome, and 4) 22 hearts from patients with hypertensive heart disease (NYHA Class II-III). Myocardial fiber hypertrophy was quantitated by measuring cross-sectional myocardial fiber diameter; the proportion of interstitial tissue was quantitated by using a computerized, high-resolution video image-digitizing system. Myocardial fiber average diameter in groups 2, 3 and 4 was significantly higher than group 1. The proportion of interstitial tissue was significantly increased in group 3. In chronic mitral incompetence an increase in left ventricular interstitial tissue may play a role in the development of severe cardiac failure.

Endomyocardiopathy with eosinophilia

Five patients were seen at the Mayo Clinic over an 8-year period with the following complex of clinical and morphologic features; striking eosinophilia, cardiomyopathy, hepatosplenomegaly, and either a rapidly fatal or a prolonged, debilitating illness. In recent years, controversy has raged over the precise designation of this syndrome, with proposals ranging from eosinophilic leukemia to hypereosinophilic syndromes. To focus on the major target organ of the disease, we have favored the term endomyocardiopathy with eosinophilia. Experience with these five patients showed that (1) eosinophilia can persist for many years before symptoms appear; (2) progressive restrictive cardiac disease was the major cause of death and debility; (3) osmiophilic cytoplasmic inclusions are present in eosinophils of these patients and also in cells from other patients with marked eosinophilia; and (4) echocardiography may prove to be a useful noninvasive tool to diagnose and follow the progress of cardiac involvement. Although none of these patients was thought to have leukemia, intensive therapy with steroids or cytotoxic agents, or both, is considered necessary to control the progression of the disease.

Neonatal necrotizing enterocolitis--a personal experience

An increasing incidence of neonatal necrotizing enterocolitis over a 2 1/2 year period is demonstrated. Following a brief discussion of pathogenic and etiologic factors, 41 cases are reviewed retrospectively. Clinical, laboratory, and radiographic diagnostic aids are discussed. Surgical and nonsurgical methods of therapy and their results are presented. In conclusion, guidelines and indications for conservative and operative treatment are outlined.

The effects of training specific mnemonics on the metamnemonic efficiency of retarded children

The effects of training specific mnemonic skills on recall readiness were evaluated in 2 groups (MA 6, MA 8) of educable retarded children. Equal numbers of S at each age were instructed in an anticipation, rehearsal, or label strategy. On the first posttest (prompted), label training did not affect performance, but anticipation and rehearsal training facilitated recall readiness estimation for both younger and older children. However, on 2 subsequent posttests (unprompted, 2 days and 2 weeks after training), the younger S returned to their pretraining competency, while the older group maintained high performance. Consideration of observational data suggested that overt activity related to the trained mnemonic correlated with recall readiness efficiency for the older but not the younger group. Even though younger children produced the strategy, the failed to monitor its effectiveness. The implications of training specific mnemonic skills are discussed in relation to developing metamnemonic efficiency.

The objective measurement of mental performance in cerebrovascular disease. A double-blind controlled study, using a graded-release preparation of isoxsuprine

An automatically controlled learned task was used to assess objectively the mental performance of a number of geriatric patients with cerebrovascular disease. The effect on the performance of the patients during treatment with isoxsuprine hydrochloride in a sustained-release presentation ("Duvadilan Retard") was measured during a double-blind, placebo-controlled trial of sixteen weeks' duration. There was a significant difference in the improvement in performance between the treated and untreated groups; by the end of the trial, the treated group having statistically significantly better scores (P = 0.047 two-tailed tests).

Ultrastructural morphometry of the blood-air barrier in pulmonary sarcoidosis

Stereologic techniques were utilized in an electron microscopic study of biopsy samples obtained from the lungs of seven patients with pulmonary sarcoidosis. Relative fractional volumes of alveolar septal components and the arithmetic mean thickness and harmonic mean thickness of alveolocapillary membranes (blood-air barrier) were compared with values for normal lungs. Based on morphometric analysis, increases in the arithmetic mean thickness and the harmonic mean thickness of the alveolocapillary membranes appeared too small to account for the reduction in gas transfer present; however, there was a quantitative relative increase in interstitial tissue in alveolar septa, which does not take part in gas exchange, at the expense of the capillary bed, which is critical to this function.

Evaluation of environmental carcinogens for cancer in man

The problem of the presence of carcinogens in the environment has become of considerable concern to the public, as it has been to the biomedical community for some time. The burden of identifying carcinogenic agents and determining threshold levels, if they exist, falls upon the scientific community. Particular care must be exercised in the design, conduct and analysis of experiments directed toward the identification of carcinogens. The data generated from such tests provides the basis for regulatory decisions by governmental authorities. The advice provided by scientists must be based on sound data. There have been instances, however, and there will be others, in which biological variability and the limits of sensitivity of our tests will give equivocal results. It is the duty of scientists to bring such uncertainties to the attention of the public while working towards the development of more sensitive and precise techniques.

Fine structural morphometry of diffuse lung diseases with abnormal blood-air gas transfer

Samples of lung biopsy tissue from nine patients with normal lungs, seven with pulmonary sarcoidosis, nine with diffuse interstitial pulmonary fibrosis, seven with histiocytosis X, and one with asbestosis were analyzed by morphometric techniques applied to electron micrographs, and the results were subjected to rank-sum analysis. Within the limits of the sampling method and the mathematical predictions of others, the general rejection of the constructed hypothesis in this study supports the conclusion that factors other than increase in the arithmetic of harmonic mean thickness of the blood-air barrier are critical to impaired gas transfer in the diseases studied.

Application of ultrastructural morphometry to lung biopsy specimens in pulmonary histiocytosis X

Stereological techniques were applied to an electron microscopic study of biopsy samples from nine human lungs with diffuse pulmonary histiocytosis X, and the results were compared with values for normal lungs. This made possible a morphometric analysis of the tissue changes associated with the measurable abnormalities in gas transfer present in this disease. The small increases in arithmetic mean thickness of the alveolar-capillary membranes appeared insufficient to account for the reduction in gas transfer present. When compared with normal lung, a threefold increase in volumetric fraction of septal intercapillary tissue was found along with a corresponding decrease in septal capillaries. While uniformity of distribution cannot be determined by this method, it appears that abnormalities of blood gas transfer in this disease result primarily from a decrease in the available diffusing surface and the ventilation-perfusion distrubances with which these tissue changes are associated.

Ultrastructural morphometry of the diffusion surface in a case of pulmonary asbestosis

A combination of electron microscopy and stereologic principles has allowed an evaluation of the contribution of structures in the blood-air barrier to gas exchange across it. In the present study this method was applied to biopsy material from the lungs of a patient with asbestosis. Within the limits of the sampling method, the results of the study are interpreted to indicate that measurable diffusion abnormalities were principally due to changes other than an increase in membrane thickness.

Retrograde pancreatography in autopsy specimens

Sixty-two pancreases were dissected at autopsy. In 55 of them, the pancreatic ducts were filled with 50 per cent Hypaqje and roentgenograms were made prior to dissection. Clinical information (available in every case) was correlated with the gross and microscopic findings and findings on the pancreatograms. The anatomically and functionally predominant duct was considered the "main pancreatic duct" regardless of its embryologic development. The common bile and main pancreatic duct opened independently into the duodenum in 8 of the 62 cases (13 per cent). The accessory pancreatic duct had a patent orifice into the duodenum in 12 of 57 cases (21 per cent). The ampulla of Vater was well developed in only 4 of the 62 cases (6 per cent), but an ampullary dilatation was present twice as often at the end of the acessory pancreatic duct, in both those that ended blindly and those that opened into the duodenum. The orifices for the accessory duct were often tiny pinhole openings. There were 2 primary carcinomas of the pancreas, one in the head and one in the tail. The pancreatic duct was almost completely obstructed in each case. Both tumors were undifferentiated adenocarcinomas, and extravasation occurred into each one of them. Extravasation also occurred into a necrotic lymphoma involving the tail of the pancreas, and into two areas of abscess formation in another case. Diffuse, dense, fluffy opacification of pancreatic parenchyma, due to alteration in cell membrane permeability, was demonstrated in acute pancreatitis, infarction, autolysis, and overfilling of the ducts by vigorous injection. Three pancreases showed microscopic changes of chronic pancreatitis. The pancreatogram on one was normal, but the microscopic changes were minimal, and pancreatitis was not suspected clinically. The other 2 cases were symptomatic, and their pancreatograms showed strictures and irregularities of the main pancreatic duct as well as saccular ectasia was present in three additional pancreases, two of which showed squamous metaplasia of ductal epithelium without other microscopic stigmata of chronic pancreatitis and no clinical features to suggest pancreatitis. The possibilities exist that ectasia of secondary ducts and squamous metaplasia of ductal epithelium are manifestations of low-grade injury and that "subclinical pancreatitis" may be common in the general population.

Effect of development and aging on the response of canine lymphocytes to phytohemagglutinin

The stage of development and age were found to effect the responsiveness of dog T-lymphocytes to phytohemagglutinin. T-lymphocytes from beagles 0 to 4 weeks of age showed significantly less response to phytohemagglutinin (P < 0.001) than T-lymphocytes from these same dogs at 6 to 12 weeks of age. Peak response to phytohemagglutinin occurred between 6 weeks to 6 months of age, after which there was a significant correlation (P < 0.02) between increase in age and decrease in phytohemagglutinin responsiveness.