A further example of human blood group chimaerism

Blood group chimaerism was detected in a healthy fertile woman, not known to be a twin. Her peripheral lymphocytes had a male karyotype (46/XY); fibroblasts cultured from her skin had a female karyotype (46/XX). The mechanism of chimaerism could not be established.

Pharmacological effects of introducing a double bond into a binding site of oxytocin. Analogues with L-3,4-dehydroproline in position 7

The side chain of the proline residue in position 7 of oxytocin has been proposed as a binding site of the hormone for the uterotonic receptor. This is the first in a series of studies in which the possibility is explored that amino acid residues located at such sites and bearing unsaturated side chains may contribute more strongly to binding than neutral, aliphatic side chains. To test this hypothesis [7-(L-3,4-dehydroproline)]oxytocin, [1-beta-mecaptopropionic acid,7-(L-3,4-dehydroproline)]oxytocin, and [1-L-alpha-hydroxy-beta-mercaptopropionic acid,7-(L-3,4-dehydroproline)]oxytocin were prepared by the solid-phase technique of peptide synthesis. Some of the pharmacological properties of the analogues were determined, and the following specific activities, respectively, were found: rat uterotinic, 1071 +/- 59, 1066 +/- 95, 880 +/- 180; avian vasodepressor, 548 +/- 10, 1008 +/- 42, 1295 +/- 62; rat antidiuretic 5.9 +/- 0.2, 23.3 +/- 1.1, 76.7 +/- 2.3. All analogues possess a lower rat pressor activity than ocytocin. Compared to oxytocin, [7-(L-3,4,-dehydroproline)]oxytocin exhibits a parallel displacement of the cumulative uterotonic log dose vs. response curve toward lower concentration (pD2 = 9.26 vs. 8.63) but elicits the same maximum response. These data would seem to support the hypothesis that the introduction of unsatuation into binding element of a peptide hormone can enhance the affinity of the hormone for some of its receptors and thereby its selectivity.

Resolution of lipid-containing atherosclerotic lesions induced by injury

In previous experiments, injury-induced atherosclerosis has been shown to be associated with the development of fatty streaks. The findings suggested that fatty streaks might represent a stage in healing of intimal injury evolving to fibrous plaques, free of lipid. The present experiment was designed to study the incidence and evolution of these lesions during a 2-week period of lesion retrogression following removal of a catheter placed in the aorta for 1 week. The findings indicate that as fat-containing lesions, either of the thromboatherosclerotic or fatty streak varieties, decreased, the amount of nonlipid-containing fibrous lesions increased.

Thromboatheromatous complications of umbilical arterial catheterization in the newborn period. Clinicopathological study

Severe catheter-related thromboatheromatous lesions were found at necropsy in 33 of 56 infants who had umbilical arterial catheters passed during life. In infants dying within 8 days of insertion of the catheter, varying degrees of thrombosis of the aorta and its major branches were seen. With increasing thrombosis and aging of the thrombus, fatty deposits were seen first within the thrombus, and then in the intima and media. In addition there was evidence of proliferation of medial smooth muscle cells and of disruption of the medial architecture below the thrombus, characterized by the presence of abundant mucopolysaccharide. In infants who survived longer, varying degrees of organization of the thrombus could be traced, leading eventually to raised fibrous plaques with lipid and occasionally calcification. The lesions in the older infants were similar in many respects to experimental thromboatheromatous lesions produced in rabbits, and to some lesions of artheroma occurring spontaneously in humans. A wide variety of embolic phenomena were found, with features suggesting asynchrony of embolic episodes. The presence of thrombotic lesions could not be related to birthweight, Apgar scores at 1 and 5 minutes, age at catheterization, duration of catheterization, underlying disease process, age at death or the presence of hypothermia, acidosis, or anomalies in coagulation tests. There is a need for less hazardous methods of monitoring arterial oxygen tension.

Synthesis and some properties and antitumor effects of the actinomycin lactam analog, (di(1-L-alpha, beta-diaminopropionic))actinomycin D1

A lactam analog of actinomycin D (AMD) has been synthesized as a potential antitumor chemotherapeutic agent. Both L-threonine residues were replaced by L-alpha,beta-diaminopropionic acid. Starting with Nalpha-benzyloxycarbonyl-Nbeta-tert-butyloxycarbonyl-L-alpha,beta-diaminopropionic acid methyl ester hydrochloride the linear intermediate Nalpha-benzyloxycarbonyl-Nbeta-(tert-butyloxycarbonylsarcosyl-L-N-methylvalyl)-L-alpha,beta-diaminopropionyl-D-valyl-L-proline p-nitrophenyl ester was prepared by conventional methods of peptide synthesis in solution. Selective cleavage of the Nbeta-tert-butyloxycarbonyl group and lactam formation afforded the desired cyclic pentapeptide derivative. The chromophore precursor, Nalpha-(2-nitro-3-benzyloxy-4-methylbenzoyl) substituent, was introduced via its symmetric anhydride. Catalytic reduction followed by ferricyanide-mediated phenoxazinone formation provided the lactam analog, [di(1'-L-alpha,beta-diaminopionic acid)]actinomycin D ([Dpr1]2-AMD). Its binding to natural and synthetic DNA and that of an analogous L-threo-alpha,beta-diaminobutyric acid containing lactam ([Dbu1]2-AMD) compared with the binding of AMD (in which the peptides are in lactone form) was studied by circular dichroic (CD) spectroscopy. The visible and uv CD spectra of free AMD differed from those of the free lactam analogs, indicating that the asymmetric environment of the pentapeptide rings in the region of the chromophore differs in free actinomycin lactone and lactams. In the presence of calf thymus DNA, PM2 DNA, and the synthetic d(A-T)-like copolymers containing 2,6-diaminopurine (DAP), poly[d(DAP-T)], and poly[d(DAP-A-T)], the rotational strengths of the optically active transitions in the visible region of the actinomycins increased, and the CD spectra in the presence of the various DNA duplexes were qualitatively similar. The CD spectra of bound actinomycin lactams resembled the spectrum of bound AMD. This suggests that the lactone and lactam actinomycins acquire a similar environment when bound to DNA. [Dpr1]2-AMD was less cytotoxic than AMD in antibacterial assays but exhibited somewhat higher toxicity in mice than AMD. At optimal dose levels the lactam analog had little or no antitumor activity in three murine tumor systems.

Three approaches to the radioimmunoassay of human beta-thromboglobulin

Three radioimmunoassays for the measurement of beta-thromboglobulin are described. The standard method, using antiserum in solution, could be used to measure plasma concentrations of beta-thromboglobulin with the results available after 2-3 d. The use of a greater dilution of antiserum and tracer, with delayed addition of tracer, resulted in a more sensitive assay suitable for measuring b-thromboglobulin in urine. The use of a solid-couples antiserum under non-equilibrium conditions allowed the measurement of plasma levels of beta-thromboglobulin after an assay incubation time of 1 h. These three radioimmunoassay systems for beta-thromboglobulin cover the likely clinical requirements for the measurement of this platelet specific protein.

The Hamilton district program in laboratory medicine: a progress report on integration

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Regression of injury-induced atheromatous lesions in rabbits

For four consecutive weeks, 61 rabbits received weekly injections of lymphocytotoxic-positive human serum into the left carotid artery and of autologous serum into the right carotid artery as a control. Serum cholesterol and serum triglyceride levels were measured before the study, in the second and fourth weeks of the study, and weekly thereafter. The results show that repeated intimal injury caused raised, lipid-containing thromboatherosclerotic lesions and that there was a consistent regression to lipid-free fibromusculoelastic plaques from the first week after completion of the injection regimen to the fourth week. Apparently, regeneration of an intact covering cell layer resulted in the elimination of lipid deposits from raised lesions, resulting in lipid-free fibromusculoelastic plaques. In addition, fatty streaks were observed to occur during regression. A statistically significant rise in serum cholesterol level during the phase of progression of lesions and a subsequent fall during regression were observed.

Platelet aggregation secondary to coronary obstruction

From many observations made at autopsy it is apparent that thrombosis in a coronary artery is usually, if not always, associated with rupture of an atheromatous plaque. The sequelae of such rupture include hemorrhage into the plaque with further narrowing of the lumen, formation of an occlusive thrombus or of a non-occlusive thrombus. A developing thrombus in an artery undergoes fragmentation with showering of the distal microcirculation by aggregates of platelets possibly with some admixture of fibrin. In many cases of sudden cardiac death associated with severe atherosclerotic stenosis of the coronary vessels, an occlusive thrombus is not found and the myocardium shows no morphological lesion or else focal patchy early damage in the subendocardial region. One possible mechanism that might explain these findings is microembolism from mural nonobstructing coronary thrombus. Such a mechanism is well established in transient ischemia of the brain and retina related to ulcerated atheroma of the internal carotid artery. Experimental observations indicate that platelet aggregates in the myocardial circulation cause arrhythmias, sudden death, vasculitis, and myocardial ischemic damage. Induction of an occlusive coronary artery thrombus is associated with development of an infarct involving the full thickness of the myocardium. A nonocclusive thrombus is associated with either no myocardial damage or focal subendocardial ischemic injury. It is possible that further aggregation of platelets may facilitate the extension of infarction subsequent to an occlusive event, although there is little evidence on this point. A number of clinical studies show increased platelet reactivity to agents causing aggregation, such as norepinephrine or collagen, in subjects experiencing thromboembolic episodes. It seems unlikely, however, that in vitro tests of platelet function can identify or predict clinical arterial thrombotic disease, although studies of platelet survival and turnover may be more helpful. There is also evidence that platelet survival may be prolonged by drugs having a therapeutic benefit in coronary artery disease and arterial thromboembolism. There is a need for better designed and coordinated clinical trials and for better experimental approaches to explore the relationships among coronary thrombosis, embolsim of the myocardial microcirculation, myocardial ischemia, and sudden death.

Inhibition of injury induced thromboatherosclerotic lesions by anti-platelet serum in rabbits

We have previously shown that repeated or continuous intimal injury caused by an indwelling aortic catheter causes a variety of lesions in rabbits maintained on a diet unsupplemented by lipid. These include fatty streaks, lipid-free fibrous plaques and lipid-rich raised thromboatherosclerotic plaques. Whether lipid-rich raised lesions are a result of injury or co-existing thrombosis or both is not clear. The present experiment was designed to answer this question. Anti-platelet serum (APS) to washed sonicated rabbit platelets was raised in sheep. PE 60 polyethylene catheters were placed in the aortas of 35 rabbits by way of a femoral artery. The animals were randomly divided into 2 groups. The experimental group (17 rabbits) received an intravascular injection of 1.0 ml of APS followed 8 hours later by a subcutaneous injection of 0.5 ml. Thereafter, 0.5 ml APS was given subcutaneously each day for 13 additional days. The control group (18 rabbits) received no APS. Platelet counts were done prior to surgery, at 5 minutes following surgery, at 4 days, 8 days and just prior to killing. Extent of lesions was estimated by photographing the opened aortas, projecting the photographs on cardboard, cutting out the areas occupied by the different lesions and weighing the cardboard. The mean weight of raised lesions in the control group was 6 to 7 times greater than in the experimental groups. Statistical analysis of this difference based on Welsh's "t" test for unequal variances was highly significant (P less than 0.001). Platelet counts in the experimental groups varied from 0 to 20,000 at 14 days. In animals with platelet counts less than or equal to 1,000 mm3 raised lesions were completely prevented. In a second experiment the effect of APS was compared with normal sheep serum (NSS). A similarly significant inhibition of raised lesions occurred in the APS group. The extent of lesions in the NSS control was similar to that in the No-APS group of the first experiment. These findings indicate that thrombosis is more important than injury in the development of lipid-rich raised lesions.

Preparation of cross-linked dimers of pancreatic ribonuclease

The cross-linking reaction between diimido esters and ribonuclease has been studied in terms of the yield of cross-linked dimer with optimum activity toward double-stranded RNA. With dimethyl suberimidate the most satisfactory conditions were condensation for 15 min at pH 7.5-8.0 at 21 degrees C with 1.25 mol equiv of the diimido ester and a protein concentration of 6%. The dimer (yield 20%) had 19 unmodified NH2 groups out of a theoretical 20 for a molecule in which two such groups are involved in the cross-linkage; the activity toward poly(A)-poly(U) in 0.14 M salt solution by spectrophotometric assay was 8.5 times that of the monomeric enzyme toward the same substrate.

Biogenic amine control of growth hormone secretion in the fetal and neonatal rat

The development of the hypothalamic-pituitary axis for growth hormone (GH) secretion has been studied in the rat fetus and in the neonate 4, 24, 48 and 72 h after birth. Injections of the serotonin blocker cyproheptadine (Cypro) and a catecholamine, dopamine (DA), each led to reductions in the level of serum GH in 21 to 22 day fetuses and in neonates up to 3 days after birth. The O-methylated derivative of dopamine, dimethoxyphenylethylamine (DMPEA), did not alter serum GH levels from those seen in saline-treated control animals. These results indicate that biogenic amines exert control over GH secretion in the fetus, close to term, and in early neonatal period. They suggest that this control is similar to that seen in the adult rat and in man and that such control may operate through serotonin receptors.

Synthesis and antitumor activity of 2-deamino- and N2-(gamma-hydroxypropyl)actinomycin D

2-Deamino- and N2-(gamma-hydroxypropyl)actinomycin D were synthesized by modification of the parent actinomycin D molecule at the 2 position of the phenoxazinone moiety. The common intermediate was 2-deamino-2-chloroactinomycin D. Catalytic hydrogenation of this material afforded the 2-deamino derivative while treatment with gamma-hydroxypropylamine yielded the N2-(gamma-hydroxypropyl) derivative. These 2-substituted actinomycin D derivatives were less potent in microbiological assays than the parent compound. Evaluation of activity in vivo against three murine tumor systems indicated that optimal dose levels of 2-deaminoactinomydin D were 50 times greater than toxic dose levels of actinomycin D. N2-(gamma-hydroxyporpyl)actinomycin D exhibited antitumor activity similar to the parent compound.