Duchenne's cardiomyopathy in a canine model: electrocardiographic and echocardiographic studies

Thirteen dogs affected with X-linked Duchenne's muscular dystrophy and 11 female carrier dogs were studied by electrocardiography (ECG) and echocardiography. Twelve of the affected dogs were studied as immature animals and followed at 1 to 6 month intervals until they were 7 to 46 months of age. Compared with control dogs, affected dogs had significantly increased (p less than 0.02) Q/R ratios in ECG leads II, III, aVF, CV6LL (V2) and CV6LU (V4). Carrier dogs had significantly increased (p less than 0.02) Q/R ratios in leads V2 and V4. The Q/R ratio increased in three of six dogs followed up from age 6 months to greater than 2 years. The PR intervals were significantly shorter (p less than 0.02) in affected dogs. Ventricular arrhythmias were identified in four of six mature affected dogs. Two-dimensional echocardiography revealed distinctive hyperechoic lesions in 12 of the 13 affected dogs and in 6 of the 11 carrier dogs. Hyperechoic lesions corresponded to calcified myocardium and surrounding dense connective tissue. This study establishes the dog affected with Duchenne's muscular dystrophy as an animal model of Duchenne's cardiomyopathy and demonstrates that the heart in carrier dogs is affected by the dystrophic process.

The impact of quitting smoking on symptoms of chronic bronchitis: results of the Scottish Heart Health Study

Scotland has high rates of death from diseases of the respiratory system and high rates of smoking, especially among women. Data on self reported smoking and prevalence of chronic cough and chronic phlegm among 10,359 men and women aged 40-59 years were obtained from the Scottish Heart Health Study. Overall, current cigarette smokers had rates of chronic cough and chronic phlegm four to five times those of never smokers after standardisation for age (32.3% v 6.5% for men and 24% v 5.5% for women for chronic cough; 31% v 8.3% for men and 21% v 5.5% for women for chronic phlegm). Ex-smokers' symptom rates were a little above those of never smokers and were significant for chronic cough among women and chronic phlegm among men. Men had higher symptom rates than women and this was true for smokers, ex-smokers, and never smokers. The higher rates among men could not be explained by higher cotinine concentrations. Tests to detect "deceivers" among ex-smokers and never smokers using biochemical validation suggested that 87 (1.5%) respondents were in fact smoking; they were excluded from analyses. There were substantially lower rates of chronic cough and chronic phlegm within a year of stopping smoking, and two to four years after stopping 89-99% of the difference between current smokers and never smokers was accounted for (99% and 93% for men and women with chronic cough, 96% and 89% for men and women with chronic phlegm). Even 10 years after stopping, rates of symptoms among ex-smokers remained a little above those of never smokers (except for women with chronic phlegm), though these differences were not statistically significant. Former heavy smokers continued to have rates of chronic cough and chronic phlegm that were higher than those of former light and moderate smokers (though not significantly so). These are cross sectional data, but they emphasise the importance for chronic bronchitis symptoms of giving up cigarette smoking, though the amount previously smoked continues to exert a small influence.

The drinking, passive smoking, smoking deception and serum cotinine in the Scottish Heart Health Study

Following a recent claim that the use of cotinine in body fluids, to assess passive smoking and smoking "deception", was confounded by metabolic individuality, and by non-tobacco sources of dietary nicotine, particularly tea, data were examined from a large cross-sectional survey in a tea-drinking population. In 3383 men and women aged 40-59 years from the Scottish Heart Health Study, defined as non-smokers, both by self-report and by low thiocyanate and expired air carbon monoxide levels, serum cotinine showed minimal association with self-reported daily average tea consumption. However, there was a strong correlation between degree of self-reported passive tobacco smoke exposure and median serum cotinine level. In the same survey, serum cotinine in 4144 self-reported non-smokers and in 3326 smokers showed entirely different distributions, but the same range, suggesting heavy nicotine intake in some "non-smokers". These analyses confirm that cotinine levels in true non-smokers reflect far more the nicotine in inhaled ambient tobacco smoke than they do nicotine in tea. Some smoking "deceivers" have the same degree of exposure to nicotine as heavy smokers. Despite individual variability, the claim of confounding is poorly supported, and cotinine is confirmed as an indicator both of passive smoking and of smoking deception.

Translation initiation in the HEXB gene encoding the beta-subunit of human beta-hexosaminidase

The human lysosomal enzyme beta-hexosaminidase (EC 3.2.1.52) is a glycoprotein composed of dimers of alpha- and/or beta-subunits. The subunits of the enzymes are synthesized in the rough endoplasmic reticulum and transported through the Golgi apparatus to the lysosome. As such, each subunit contains an amino-terminal signal peptide that directs the nascent polypeptide into the lumen of the endoplasmic reticulum. The signal peptide cleavage site of the beta-polypeptide is known, but its NH2 terminus has not been determined due to the presence of three candidate initiation codons upstream of the cleavage site. In this study, we identified the mRNA cap site, confirming the presence of all three AUGs in the majority of HEXB mRNA. To identify the site of translation initiation, we mutated the three ATGs by deletion and site-directed mutagenesis and showed that all three AUG codons can be used for translation initiation after expression in COS cells. Furthermore, in each case, a fully processed, i.e. mature lysosomal, and enzymatically active beta-hexosaminidase was produced indicating that a functional signal peptide was synthesized. However, expression of a frameshift mutation in the normal construct, created by insertion of a single nucleotide between the first and second ATG, resulted in no significant enzyme activity or beta-subunit protein. We conclude, therefore, that the first in-frame ATG is used exclusively in vivo, in keeping with the scanning model of eukaryotic translation initiation. Interestingly, substitution of all three ATGs with CTG resulted in a significant amount of mature beta-hexosaminidase, showing that under these conditions, initiation could occur from non-AUG codons. Translation initiation from the first AUG gives the prepro-beta-polypeptide a signal peptide of 42 amino acids that has an unusually long hydrophobic core more typical of membrane spanning domains. Such a large hydrophobic core has not been found in other cleavable signal peptides.

The cost of upgrading cross-infection control in twelve community dental service surgeries, 1988-1989

A retrospective survey was established in 1989 to cost the upgrading of cross-infection control methods in twelve community dental service surgeries. The capital and maintenance expenditure averaged 3244.85 pounds per surgery, indicating that the costs might be less than currently projected.

Mitogenic effects of transforming growth factor type e on epithelial and fibroblastic cells--comparison with other growth factors

Transforming growth factor type-e (TGFe) is a novel TGF which was first described as a growth factor possibly involved in autocrine stimulation of anchorage-independent growth of carcinoma cells. Its later identification in normal tissues, plasma, and platelets suggested a role for TGFe in normal cell growth. This study shows that TGFe stimulates both anchorage-dependent and -independent growth of epithelial and fibroblastic cells of nonneoplastic origin. The mitogenic activity of TGFe in monolayer is slightly less than that of basic fibroblast growth factor, equipotent to that of epidermal growth factor, and greater than that of IGF-1. TGFe acts as a progression factor for both AKR-2B and Balb-3T3 cells. TGFe is also a potent mitogen for normal human epidermal keratinocytes and may therefore play a role in epidermal growth and regeneration.

Partitioning of amino acids in lactating cows: oxidation to carbon dioxide

The rate and extent of oxidation of 20 different amino acids has been evaluated as part of a study on partitioning of amino acids in normal lactating cows. Only four amino acids--glutamate, aspartate, alanine and glutamine--were extensively oxidized, and when expressed as a percentage of the injected dose oxidized during 3 h after intravenous injection, the value for these four amino acids was not significantly different from those obtained with the volatile fatty acids. The oxidation of all other amino acids was significantly slower, effectively prolonging their availability for protein synthesis. The pattern of oxidation among the amino acids supports the hypothesis that catabolized protein can provide a protracted source of anaplerotic precursors that augment the metabolic role of the tricarboxylic acid cycle and would have survival advantage in both acute and chronic exigencies. Glutamate and aspartate provide the earliest and largest influx to the tricarboxylic acid cycle, with alanine and, especially, glutamine appearing to serve as reservoirs of amino-nitrogen. Several dispensable amino acids are metabolized as slowly as the indispensable ones, indicating that metabolic conservation is not restricted to the latter group.

Suspected familial renal disease in chow chows

Renal disease was diagnosed in 6 young Chow Chows. Clinical abnormalities included vomiting, polyuria, polydipsia, and weight loss. Common abnormal laboratory findings were azotemia, hyperphosphatemia, hypocalcemia, nonregenerative anemia, and low urine specific gravity. All 6 dogs had similar microscopic renal lesions. characterized by interstitial fibrosis, a population of small glomeruli, and lack of inflammatory cells. A familial basis for the renal disease is suggested because of its development in 4 closely related dogs.

Introduction of the alpha subunit mutation associated with the B1 variant of Tay-Sachs disease into the beta subunit produces a beta-hexosaminidase B without catalytic activity

Lysosomal beta-hexosaminidase (beta-N-acetylhexosaminidase, EC 3.2.1.52) occurs in two major isozyme forms, hexosaminidase A (alpha beta) and hexosaminidase B (beta beta). Although dimer formation is required for enzymatic activity, both subunits contain active sites which share many common substrates. However, the alpha subunit alone confers on hexosaminidase A the specificity for negatively charged substrates, e.g. GM2 ganglioside. Recently, a point mutation, producing a single amino acid substitution in the alpha subunit (Arg178-His), has been found to be associated with the B1 variant phenotype of Tay-Sachs disease (Ohno, K., and Suzuki, K. (1988) J. Neurochem. 50, 316-318). This variant is characterized by normal levels of hexosaminidase A as measured by a common artificial substrate, but an absence of activity toward alpha subunit-specific substrates. However, because of the presence of an active beta subunit in the mutant hexosaminidase A, it has not been possible to determine whether the affected alpha subunit has undergone a change in substrate specificity or become totally inactive. In order to define the full effect of the B1 mutation we have taken advantage of the common evolutionary origin of the genes coding for the alpha and beta subunits. Since the B1 mutation occurs in a region of extended identity between the two subunits, we have duplicated the Arg178-His mutation in a cDNA coding for the human beta subunit (Arg211-His). By expression of the mutant construct in monkey COS cells we have been able to examine the effect of this mutation on beta subunits which are capable of forming stable, active homodimers, an experiment that could not readily be accomplished with heterodimeric hexosaminidase A. Our data show that beta homodimers containing the Arg211-His substitution are formed and are transported into the lysosome in a manner identical to that of normal pro-hexosaminidase B. However, the mutant homodimers are processed at a slower rate and are less stable in the lysozyme. Their most striking feature was a total lack of normal hexosaminidase B activity. We conclude that while the effect of the Arg178-His substitution is not strictly limited to the active site, the severe B1 phenotype results from a totally inactive alpha-subunit in hexosaminidase A.

A Canadian multicenter study with Zaditen (ketotifen) in the treatment of bronchial asthma in children aged 5 to 17 years

One hundred thirty-eight children with chronic asthma, requiring daily treatment with bronchodilators, took part in a 7-month, double-blind, multicenter clinical study. Patients were randomized into two groups, and after a 1-month baseline, were administered Zaditen (ketotifen), 1.0 mg twice daily, or an identical placebo for a period of 6 months. After 10 weeks of receiving the study medication, bronchodilator use was reduced or stopped. In the Zaditen-treated group, 60% of the children taking theophylline were able to stop its use completely, compared to 34% of the patients taking placebo (p less than 0.05). Of the patients who were unable to stop taking theophylline, the Zaditen-and placebo-treated groups recorded average dosage reductions of 62% and 26%, respectively. These differences were statistically significant (p less than 0.05). Thus, a high percentage of patients in the placebo-treated group maintained asthma symptom control with theophylline, whereas most of the Zaditen-treated patients could stop using this medication. Although pulmonary function readings improved in both groups, those patients taking Zaditen demonstrated earlier improvement and greater changes from baseline. Significant differences (p less than 0.05) in favor of Zaditen were found for reduction of concomitant medications, patient's global evaluation, physician's clinical evaluations, incidence of emergency room visits for asthma, and upper respiratory tract infections. No unexpected side effects were observed. It is concluded that Zaditen is an effective medication for long-term control of asthma in children.

Clinical significance of mildly elevated thyrotropin levels with normal thyroxine levels

The meaning of minor elevations in the thyrotropin level (less than 10 mIU/ml) in association with a normal thyroxine level has been questioned. Although such findings are presumed to be indicative of subclinical hypothyroidism, consideration of other causes can pose problems with diagnosis. We investigated the clinical significance of equivocal elevation of thyrotropin values with a normal thyroxine level and free thyroxine index in 31 patients evaluated with a thyrotropin releasing hormone (TRH) stimulation test and antithyroid antibody determinations. Patients were categorized as euthyroid or hypothyroid on the basis of TRH responsiveness. Of the 31 patients, 23 (74%) were hypothyroid, resulting in a positive predictive value as high as 81%. Eight of 21 hypothyroid patients (38%) had antimicrosomal antibodies, and only one euthyroid patient had antimicrosomal antibodies. We find that equivocally elevated thyrotropin values indicate primary hypothyroidism about 80% of the time. The combination of a mildly elevated thyrotropin level and antimicrosomal antibodies is seen almost exclusively in patients with thyroid failure.

Membrane topology of mammalian cytochromes P-450 from liver endoplasmic reticulum. Determination by trypsinolysis of phenobarbital-treated microsomes

We have studied the membrane topology of liver microsomal cytochromes P-450 derived from phenobarbital-treated rabbits via trypsinolysis of intact microsomes, recovery of solubilized peptide fragments by ultracentrifugation and liquid chromatography, primary structure determination by Edman microsequence analysis, and database searching to match isolated fragments with parent sequences. Relative to the primary structure of isozyme 2, the major phenobarbital-inducible form, fragments were isolated beginning at residues Glu86, Ile101, Arg126, Cys152, Leu198, Ser211, Asn237, Glu327, Asn385, Thr407, Phe408, Phe413, and Thr444. Such results show that this family of structurally related cytochromes is bound to the endoplasmic reticulum membrane by only one or two transmembrane segments, located at the NH2-terminal end of the polypeptide chain. The remainder of the protein, from residue approximately 50 to the COOH terminus must exist as a catalytic, heme-containing domain exposed on the cytosolic side of the membrane. Furthermore, our results indicate that the catalytic domain must be peripherally associated with the membrane surface. This would imply that substrates might have access to the active site of the cytochrome P-450 either by diffusion from the cytosol or from within the lipid bilayer.

Improved cryopreserved semen fecundability in an alternating fresh-frozen artificial insemination program

This study with glycerol and increased number of motile sperm inseminated showed an increase in f to 10.4% for frozen semen and 27.4% for fresh semen. There is a significant (P less than 0.01) difference in pregnancy rate when greater than 100 million motile sperm are inseminated (31.3%) than when less than that number are inseminated (11.9%) in the first cycle when frozen semen is used.

Evaluation of the stable fly (Stomoxys calcitrans) as a vector of enzootic bovine leukosis

Experiments reported here were directed at 2 questions: (1) Can the stable fly (Stomoxys calcitrans) transmit enzootic bovine leukosis? (2) Could early viremia augment the probability of transmission by this insect? In one vector experiment, calves and bovine leukemia virus (BLV)-infected cows were housed with and without stable flies. The calves were monitored serologically during a 3-month postexposure period, using the agar gel immunodiffusion test. All fly-infested and fly-free calves remained BLV-seronegative. For a second vector experiment, donor calves, newly injected with blood from BLV-infected cows with high virus expression, were tethered alternately between uninoculated, weaned BLV-seronegative calves. These groups were housed with or without flies in 2 replicate trials. The inoculated calves from the first replicate seroconverted at 16 and 23 days after inoculation; the inoculated calves from the second replicate seroconverted at 11, 16, 16, and 37 days after inoculation. All uninoculated calves remained BLV-seronegative. In a manual transmission experiment, 50 unfed stable flies were allowed to complete a meal on each of 3 BLV-seronegative calves after feeding on a BLV-seropositive cow with high (42%) virus expression. One control calf was injected with blood from the cow. Seroconversion occurred in the control calf and 1 calf on which flies were given access. A scanning electron microscopic study was made of the everted and closed mouth parts of the stable fly. Given the lymphocyte count in blood from the cow used in the manual vector transmission experiment, it was calculated that 3,950 mouth part volumes would be necessary to transmit BLV.(ABSTRACT TRUNCATED AT 250 WORDS)

Freezing of mammalian embryos without the aid of a programmable freezer

A simple, inexpensive and repeatable method of freezing/thawing (F/T) mammalian concepti was developed with the use of 2-cell mouse embryos. Cryoprotectants, length of exposure to protectants, and subzero holding times before liquid nitrogen (LN2) exposure were examined in an effort to obtain an effective freezing protocol. Sequential examination of these variables provided data suggesting that 3.5 M dimethyl sulfoxide (DMSO) plus 0.25 M sucrose exposure for 5 minutes at room temperature, followed by a -30 degrees C environment for 90 minutes, best prepared embryos for LN2 storage. After thawing and culture, 48 of the 93 (52%) embryos developed to the blastocyst stage.

Incontinentia pigmenti: the development of pseudoglioma

A case is described of incontinentia pigmenti in an infant with relatively normal retinae at seven days after birth who went on to total blindness by three months. This was due to excessive neovascularisation of retinae and vitreous, leading to bilateral pseudoglioma.

Inhibition of in vitro mitogen-induced lymphoproliferative responses by sera from F344 rats with large granular lymphocyte leukemia

The effect of large granular lymphocyte leukemia on F344 rat lymphocytes was studied by analyzing the blastogenic responses of normal spleen cells exposed to serum from leukemic rats. Sera from both transplanted as well as spontaneous cases of LGL leukemia markedly depressed the response to ConA and PHA. The suppressive activity was heat-stable at 56 degrees C, non-dialyzable and was effective even when added to lymphocytes only during the last 24 hrs of culture. A similar depression of blastogenesis was caused by sera from nonleukemic fasted rats. Depletion of lipoproteins from sera partially relieved the suppression. Leukemic and fasted rats had nearly identical serum lipoprotein electrophoretic profiles, indicating that abnormal lipoprotein metabolism may result from the severe anorexia which characterizes the terminal stages of the disease and may cause immunosuppression. Residual suppressive activity was also found in lipoprotein depleted sera. Supernatant fluids from spleen cell cultures of some leukemic rats also depressed lymphocyte blastogenic responses when compared to supernatants from normal spleen cultures.

Circumcision decision: prominence of social concerns

Despite policy statements against routine circumcision of newborns by the American Academy of Pediatrics and the American College of Obstetrics and Gynecology more than 10 years ago, there has been virtually no change in circumcision practices in the United States. In addition, controlled trials of programs to educate parents about the lack of medical indications for routine newborn circumcision have shown that parental education has little impact on the circumcision decision. We hypothesized that parents based their circumcision decision predominantly on social concerns rather than on medical ones. We prospectively surveyed parents of 124 newborns soon after they made the circumcision decision to learn their reasons for the decision. The strongest factor associated with the circumcision decision was whether or not the father was circumcised (P less than .0001). The survey also showed that concerns about the attitudes of peers and their sons' self concept in the future were prominent among parents deciding to circumcise. The circumcision decision in the United States is emerging as a cultural ritual rather than the result of medical misunderstanding among parents. In counseling parents making the circumcision decision, the health care provider should provide a knowledgeable and honest discussion of the medical aspects of circumcision. Until information is available that addresses parents' social concerns about circumcision, it is unreasonable to expect a significant change in circumcision customs in the United States.

Sucrose-induced obesity: effect of diet on obesity and brown adipose tissue

Adult male Sprague-Dawley rats were divided into three groups and fed diets containing either 10, 20, or 40% protein for 56 days. Half of the rats in each dietary condition were given a 32% sucrose solution plus the standard diet and water. Sucrose intake varied directly as a function of dietary protein levels. Rats fed either the 10 or 20% protein diet and sucrose had higher caloric intakes, gained more weight, were more efficient at using calories for weight gain, and had more adipose tissue than rats given the same diet without sucrose. Rats fed the 40% protein diet and sucrose did not exhibit overeating, excess weight gain, or increased feed efficiency relative to animals fed the 40% diet alone. Animals given sucrose had more interscapular brown adipose tissue (IBAT) and a greater metabolic potential for thermogenesis in IBAT as determined by GDP binding in mitochondria than rats not fed sucrose. These results demonstrate that dietary protein is important in the development of sucrose-induced obesity and that increases in IBAT mass and activity can occur concomitant with increased feed efficiency.

Relationship of milking rate to somatic cell count

Information on milking rate, monthly bucket somatic cell counts, mastitis treatment, and milk production was obtained from 284 lactations of Holstein cows separated into three lactation groups. Significant correlations between somatic cell count (linear score) and other parameters included production in lactation 1 (-.185), production in lactation 2 (-.267), and percent 2-min milk in lactation 2 (.251). Somatic cell count tended to increase with maximum milking rate in all lactations, but correlations were not statistically significant. Twenty-nine percent of cows with milking rate measurements were treated for clinical mastitis. Treated cows in each lactation group produced less milk than untreated cows. In the second and third lactation groups, treated cows had a shorter total milking time and a higher percent 2-min milk than untreated cows, but differences were not statistically significant. Overall, the data support the concept that faster milking cows tend to have higher cell counts and more mastitis treatments, particularly beyond first lactation. However, the magnitude of the relationship was small.

The effect of oral Mycobacterium vaccae on subsequent responses of mice to BCG sensitization

It has been postulated that previous exposure to mycobacteria in the environment may be a contributing factor to the variable efficacy of BCG vaccination in protecting against human tuberculosis or leprosy, in different geographical regions. To test this hypothesis mice were given Mycobacterium vaccae in their drinking water for 3 weeks immediately, 27 days, or 54 days before they were injected subcutaneously with BCG. Spleen cells were examined, 50 days after injection of the mice, for ability to proliferate in vitro in response to killed mycobacteria added to the cultures. The results show that, depending on the timing of the exposure of the mice in vivo to M. vaccae before BCG injection and the dose of the mycobacterial challenge in vitro, oral administration of this species of environmental mycobacteria can either enhance, mask or interfere with the expression of sensitization by BCG. Thus, our data from mice support the hypothesis that the results of BCG vaccination for a particular human population are influenced by exposure to indigenous mycobacteria.

Behavior of transplanted large granular lymphocyte leukemia in Fischer 344 rats

The behavior of transplanted large granular lymphocyte leukemia was studied by isogeneic inoculation of 55 young F344 rats. A high percentage of transplants were successful, showing a dose-dependent latent phase followed by weight loss, exponential increase of tumor cells, and widespread infiltration. Serial passage of tumor cells appeared to increase malignancy by decreasing longevity. Grossly, there was splenomegaly, variable lymphadenopathy, and petechial hemorrhages on the lungs, lymph nodes, and brain. Diffuse infiltration of tumor cells caused morphologic changes identical with spontaneous large granular lymphocyte leukemia including splenic lymphoid depletion, hepatocellular necrosis, tumor cell erythrophagocytosis, and femoral medullary endosteal bone proliferation. Clinicopathologic features were also similar to spontaneous large granular lymphocyte leukemia. There was immune-mediated hemolytic anemia and thrombocytopenia, which coincided with development of leukemia, as well as hyperbilirubinemia and elevated serum enzymes, indicative of liver disease. It was concluded that isogeneic transplantation of large granular lymphocyte leukemia is not only highly successful but reproduces the pattern and clinical syndrome of the spontaneous tumor including the important paraneoplastic syndrome of hemolytic anemia and thrombocytopenia.

Johannesburg Hospital neonatal statistics--1983

An analysis of Johannesburg Hospital neonatal admissions and deaths is presented for the period 1 January-31 December 1983. Infants weighing less than 1 500 g accounted for 25% of admissions and 47% of deaths. Compared with a previous report, a 68% increase in the admission of neonates weighing less than 1 000 g is shown. This increase probably reflects a more aggressive approach to the treatment of infants in this weight category. Despite a protracted period of hospitalization for survivors and some of those who did not survive, intensive care of the infant of very low birth weight (VLBW) appears to be justified, since: the major causes of death in this group are related to prematurity and are potentially preventable; and preliminary studies of VLBW survivors suggest a favourable outcome.

Mycobacterium bovis, BCG, modulation of murine antibody responses: influence of dose and degree of aggregation of live or dead organisms

Mycobacteria have the ability to enhance or depress immune responses. This paper describes experiments designed to investigate the parameters determining the direction of modulation. It has been shown previously that 10(8) liver Mycobacterium bovis BCG depress the ability of mouse spleen cells to produce a primary antibody response in vitro to SRBC 2-3 weeks after i.v. injection, whereas the same number of dead organisms enhance this response. Using the same growth medium for the BCG (Glaxo glycerol-free medium), we now find that decreasing the BCG dose to mice from 10(8) to 10 (6) liver organisms results in enhanced responses and increasing the dose to more than 10(8) dead organisms results in depressed responses. It thus appears that bacterial load is the important factor determining whether depression or enhancement of the primary antibody response will occur, rather than the viability of the organisms per se. However, when the BCG was grown in Middlebrook 7H9 broth, doses as high as 4 X 10(9) dead BCG/mouse failed to depress although depressed responses were found if sufficient live organisms (7 X 10(8)) were injected. In view of the known growth characteristics of BCG in these 2 bacteriological media, it is suggested that the degree of aggregation of the injected suspension may also be of importance in determining whether or not depression will occur. A comparison of the effects of BCG injected untreated or after dispersion of bacterial aggregates supports this idea. Some degree of splenomegaly was always found in mice with depressed splenic responses but a large spleen did not necessarily yield cell suspensions with depressed responses.

An empirical comparison of backtracking algorithms

In this paper we report the results of experimental studies of zero-level, one-level, and two-level search rearrangement backtracking. We establish upper and lower limits for the size problem for which one-level backtracking is preferred over zero-level and two-level methods, thereby showing that the zero-level method is best for very small problems. The one-level method is best for moderate size problems, and the two-level method is best for extremely large problems. Together with our theoretical asymptotic formulas, these measurements provide a useful guide for selecting the best search rearrangement method for a particular problem.

Production of kidney tumors in rats with low dose of dimethylnitrosamine after partial hepatectomy

The occurrence of kidney tumors in inbred Wistar rats as a result of dimethylnitrosamine (DMN) administration at different intervals after partial hepatectomy was studied. The schedule for DMN administration was determined on the basis of the levels of liver dimethylnitrosamine demethylase (DMN-d) at different intervals after the operation. DMN-d was 62% of the control values at 24 hours. 72% at 72 hours, and 96% at 92 hours after the operation. At these intervals a single dose of DMN (10 mg/kg body wt) was given to partially hepatectomized animals and to untreated controls. At termination, when the animals were 94 weeks old, no kidney tumors were found in the control animals, whereas 23 of 54 animals (43%) that had been given injections of DMN 24 hours after partial hepatectomy developed kidney tumors. Kidney tumor incidence was 28 or 12%, respectively, when the carcinogen was administered 72 of 92 hours after the operation. The kidney tumor incidence and the activity of liver DMN-d were inversely related.

Enlargement of carotid bodies in rats with lung emphysema or silicosis

Volume of carotid bodies was measured morphometrically in rats with experimental lung emphysema or silicosis. The mean volume of the left carotid body was 19.9 +/- (SD) 12.4 in 13 control rats, 30.7 +/- 12.5 in 9 rats with lung emphysema, and 41 +/- 18.9 . 10(6) micrometer 3 in 10 rats with lung silicosis. There was no correlation between carotid body volume and pulmonary arterial blood pressure. A good correlation was found between the volume of carotid body and partial pressure of oxygen in arterial blood. The functional meaning of the increase of volume of carotid bodies in rats with chronic respiratory insufficiency remains unclear.

Prospective study of medical and urgent surgical therapy in randomizable patients with unstable angina pectoris: results of in-hospital and chronic mortality and morbidity

At the Massachusetts General Hospital, all 190 patients who presented with the clinical and ECG criteria of the national Unstable Angina Pectoris Study (NUAPS) for unstable angina pectoris (UAP) were prospectively evaluated from their entrance between 1972 and 1976 (the entry period for NUAPS). Coronary angiography was performed in 166 patients. Of these, 83 patients (50%) were not eligible for randomization because of obstruction in the left main coronary artery (4%), inoperable diffuse coronary disease (11%), failure of initial medical therapy (20%), minimal coronary disease (13%), or other reasons (2%). The other 83 patients (50%) were eligible for randomization by NUAPS criteria; 39 received medical therapy and 44 underwent urgent coronary artery bypass surgery (CABG). The medical and surgical patients were comparable in terms of clinical characteristics and extent of anatomical disease. In-hospital (3% medical and 2% surgical) and late (5% medical and 5% surgical) mortality were similar over a mean follow-up period of 46 months. Myocardial infarction rate was statistically similar in-hospital (5% medical and 11% surgical) and during chronic evaluation (5% medical and 14% surgical). However, late severe angina (NYHA class III or IV) occurred in a significantly higher percentage of medical patients (28% medical versus 9% surgical; p less than 0.05) and nine medical patients (23%) required late elective CABG for relief of persistent angina. This experience is comparable to NUAPS, and supports the conclusion that acute management of unstable angina pectoris may begin with intensive medical treatment followed later by more elective CABG for those patients with persistent angina despite medical therapy.

2,4-diaminoanisole-induced thyroid pigmentation in rats inhibited by m-phenylenediamine

The effect of the carcinogenic hair dye component 2,4-diaminoanisole (2,4-DAA) on thyroid and pituitary morphology was studied. Heavy pigmentation of the hypertrophied thyroid epithelium was present when the animals were fed with 2,4-DAA for 6 weeks. Another hair dye component m-phenylenediamine (m-PDA), which lacks the methoxy group, and which is not carcinogenic, prevented the dark pigmentation of the thyroid epithelium caused by 2,4-DAA, but had only a slight effect on the hypertrophy of the gland. In the pituitary gland of 2,4-DAA-fed animals only a few aldehyde fuchsin positive thyrotrope cells were present. When 2,4-DAA and m-PDA were fed simultaneously, the number of hypertrophied chromophobic cells was greatly increased and the aldehyde fuchsin-positive cells were practically absent.