The anatomical aspects of minimally invasive cardiac valve operations.

Cadaveric dissections were carried out to examine the relationship of the cardiac valve structures to the surface anatomy of the chest as it relates to our approaches to minimally invasive valvular operations. The techniques of upper hemisternotomy and lower hemisternotomy as used at our institution are described.

Inhibition of Dunning tumor growth by melatonin.

Injections of the pineal hormone melatonin reduced growth and increased doubling time of the R3327H Dunning prostatic adenocarcinoma in the Copenhagen X Fisher rat. This occurred even though testosterone levels (50% of normal) were ostensibly high enough to maintain normal tumor growth. Melatonin may act directly upon the conversion of testosterone to dihydrotestosterone to inhibit tumor growth. Alternatively, a more complicated mechanism may be involved since studies on MCF breast cancer tissue indicate an estrogen requirement for inhibition of growth by melatonin.

Bioelectrochemical enzyme immunoassay of human choriogonadotropin with magnetic electrodes.

We describe an amperometric technique for quantification of an enzyme immunoassay in which we use a magnetic working electrode, both to separate bound and free analyte and to monitor the electrochemical response. We used a "two-site" immunometric assay with monoclonal antibodies for human choriogonadotropin (hCG) as a model system in which magnetic particles were used as the solid phase. Separation of bound and free label is readily achieved by localizing the particles at the electrode. Activity of the bound enzyme in the environment of the electrode is determined electrochemically, permitting rapid quantification of the analyte without the need for a separate incubation step to measure enzyme activity. The sensitivity of the system is 150 int. units of hCG per litre (1st Int. Ref. Preparation). Correlation between the amperometric measurement of urinary hCG and data for an immunoradiometric assay was r = 0.9. The assay is rapid, requiring a total assay time for each sample of 20 min, which includes 15 min for antibody/antigen binding.

Catecholamines and pinealectomy-induced convulsions in the gerbil (Meriones unguiculatus).

Within three hours after surgery nine out of ten pineal-ectomized gerbils will convulse; dopamine (DA) levels in the telencephalon of the gerbils do not change after pinealectomy (PX), however, norepinephrine (NE) concentrations decrease in the telencephalon from 1-12 hours after PX (Philo and Reiter, 1980). Administration of L-dihydroxyphenylalanine (L-DOPA, 50 mg/kg) will prevent the convulsions and maintain normal levels of norepinephrine. Administration of alpha-methyl-p-tyrosine (alpha MPT, 250 mg/kg), a tyrosine hydroxylase inhibitor, increases the number of convulsions. Injections of L-DOPA counter the facilitatory actions of alpha MPT on PX-induced convulsions. Studies with the monoamine oxidase inhibitor pargyline indicate a decrease in production of norepinephrine after PX in the gerbil. The diminished levels of neurotransmitter apparently facilitate the onset of convulsions caused by the epileptogenic stimulus of PX.

Comparison of antithrombin III assays using biological and chromogenic substrates.

Antithrombin III (At III) levels in plasma samples were determined by incubation of diluted plasma with thrombin, either with or without heparin. Followed by measurement of residual thrombin using clotting and amidolytic methods. All assays were of multidose bioassay design suitable for parallel line analysis. Assays without heparin showed only a small difference between amidolytic and clotting methods, which was not significant at the 95% level. Assays with heparin showed a much larger difference between clotting and amidolytic methods which is shown to be attributable to the heat defibrination step used in the clotting assay. Heat defibrination and ancrod defibrination methods are compared using the amidolytic heparin cofactor assay and it is shown that heat defibrination can cause the loss of nearly 50% of the functional At III in a reconstituted freeze-dried plasma which was used as a standard. No loss occurs when ancrod is used for defibrination. It is an advantage of the amidolytic heparin cofactor assay that defibrination is not required.

The involvement of brain amines in pinealectomy-induced convulsions in the gerbil: I. Serotonin.

Pharmacological induction of changes in the serotonergic system was used to study the involvement of telencephalic serotonin (5-HT) in pinealectomy (PX) induced convulsions in the gerbil (Meriones unguiculatus). The reactions of the catecholamines norepinephrine (NE) and dopamine (DA) to both PX and drug treatment were also studied. Serotonin is apparently of little importance in the PX-induced convulsion since the artificial elevation by administration of tryptophan and 5-hydroxytryptophan, or depression by treatment with p-chloramphetamine, of telencephalic 5-HT had little effect on the convulsions. In other models for the study of epilepsy, lowered 5-HT results in an increase in seizure intensity. In this study, as in previous ones, telencephalic NE was repeatedly and significantly lowered after PX. None of the serotonergic drugs resulted in changes in NE. Data such as presented here are supportive of previous reports which indicate that a depression of NE facilitates convulsions.

Plasmin potency estimates: influence of the substrate used in assay.

A urokinase-activated plasmin (UK-plasmin) preparation was assayed against the International Reference Preparation for Plasmin (IRP-plasmin) using caseinolytic, fibrinolytic, fibrinogenolytic and chromogenic assay methods. The relative potency (using multi-dose bioassays) was estimated by the fibrinolytic method to be about twice that obtained by the caseinolytic, fibrinolytic and chromogenic assay methods. It was found that the UK-plasmin binds to fibrin to a greater extent than does the IRP-plasmin and this is advanced as an explanation for the discrepancy between assay methods. This difference in the binding of the two plasmins to fibrin may mean that it will be difficult to compare the fibrinolytic activities of various plasmin preparations. It is also shown that, during thermal degradation, the IRP-plasmin loses fibrinolytic activity more rapidly than amidolytic activity.

Influence of the pineal gland on the reproductive system of the male house mouse.

Procedures designed to express pineal-mediated antigonadotropic activity were performed upon male house mice. Neither blinding nor blinding plus olfactory bulbectomy of house mice resulted in testicular involution within 12 weeks. The pineal gland appears to be of little significance to reproduction in the house mouse.

A circannual rhythm in bovine pineal serotonin.

Bovine pineal serotonin (5-HT) was analyzed at the time of the solstices and equinoxes from December, 1975 until June, 1978. The highest values of 5-HT were detected at the winter solstices and lowest values at the summer solstices of each year examined. The peaks in bovine pineal 5-HT correspond with a lessened fertility in cattle reported during the winter months.

Antiepileptic effects of melatonin in the pinealectomized Mongolian gerbil.

Pinealectomy of the Mongolian gerbil leads to seizure activity. The pineal gland is a major source of malatonin (5-methoxy-N-acetyltryptamine) which may possess a modulatory influence upon neural activity. Melatonin administered in the form of subcutaneous beeswax implants was given to gerbils four days prior to pinealectomy or sham pinealectomy. Beeswax pellets were implanted as the vehicle agent in respective groups. Melatonin-treated pinealectomized animals exhibited fewer seizures than did pinealectomized animals that did not receive melatonin. The results indicate that melatonin has an ameliorative effect upon pinealectomy-induced seizures, but the mechanism by which pinealectomy induced the seizures, and the etiology in which melatonin reduces the seizure activity is unknown.

The pineal body and pinealectomy in the cotton rat, Sigmodon hispidus.

The pineal body is known to be an important component in the regulation of seasonal reproduction. The gross morphology of the rodent pineal gland is highly variable and this variability may be related to the degree of its involvement in regulating reproduction. The size and complexity of the pineal gland of the cotton rat appear to be well correlated with the known reproductive responses of this species to photoperiod. The cotton rat pineal is a large (2,500 micrometer X 500 micrometer) mass originating from the dorsal diencephalon and extending dorsally to the superior sagittal sinus. The cotton rat pineal is solid and cannot be divided into deep and superficial portions as in some rodents. Animals obtained from the field were found to survive conventional pinealectomy when it was carried out under methoxyflurane anesthesia. These results indicate that the cotton rat could be used as a wild animal model for pineal gland-seasonal reproduction research.

Changes in brain dopamine, norepinephrine and serotonin associated with convulsions induced by pinealectomy in the gerbil.

In three separate experiments, adult male gerbils 10 weeks of age were pinealectomized (PX), observed for convulsions, and sacrificed at various intervals after PX. Norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in selected brain parts were determined by fluorometric procedures. No changes in DA were observed. Serotonin levels were shown to be elevated in sham-operated and PX animals, possibly due to stress phenomena associated with anesthesia or surgical procedures. Norepinephrine was significantly depressed over control and sham-operated animals by 1 hour after surgery with a post-operative duration of at least 12 hours. Results in this study did not indicate whether the decreased NE was the cause or an effect of the PX-induced convulsive activity.

Characterization of pinealectomy induced convulsions in the Mongolian gerbil (Meriones unguiculatus).

The Mongolian gerbil (Meriones unguiculatus) exhibits convulsions after pinealectomy (PX). Included in the convulsions are wild running, tonic-clonic activity, and occasionally death. This paper reports various parameters that influence the convulsions. Animals 60 and 90 days old have a shorter latency to onset of convulsions than do 30-day-old gerbils. Animals pinealectomized at the onset of light (0600) in an LD 14:10 photoperiod have a shorter latency to onset and greater number of convulsions than animals pinealectomized at other times. Modulation of the photoperiod to LD 20:4 and 4:20 does not affect the convulsions. Superior cervical ganglionectomy (SCGX) does not result in convulsions; subsequent PX of the SCGX animals does. Replacement of pineal extract does not prevent the convulsions. The PX induced convulsion in gerbils resembles the parathyroidectomy-pinealectomy induced convulsion in the rat in all aspects, but with a shorter latency to onset.

The membrane potential of mouse ascites-tumour cells studied with the fluorescent probe 3,3'-dipropyloxadicarbocyanine. Amplitude of the depolarization caused by amino acids.

1. The magnitude of the K+ gradient across the plasma membrane, which was in equilibrium with the membrane potential (E) of the tumour cells, was determined by the "null point" procedure of Hoffman & Laris (1974) [J. Physiol. (London) 239, 519--552] in which the fluorescence of the dye serves as an indicator of changes in the magnitude of E. 2. A mixture of oligomycin, 2,4-dinitrophenol and antimycin was used to stop the mitochondria from interfering with the fluorescence signal. Transport functions at the plasmalemma were maintained under these conditions in the presence of glucose. 3. Physiological circumstances were found in which incubation with glycine or with glucose changed the "null point" value of E within the range--20mV to--100mV. The fluorescence intensity at the "null point" was an approximately linear function of E over that range. The procedure enabled E to be inferred form the fluorescence intensity in circumstances where titration to the "null point" was not feasible. 4. The rapid depolarization caused by l-methionine or glycine was shown in this way to have a maximum amplitude of about 60mV. A mathematical model of this process was devised. 5. The electrogenic Na+ pump hyperpolarized the cells up to about --80mV when the cellular and extracellular concentrations of K+ were roughly equal. 6. The observations show that the factors generating the membrane potential represent a major source of energy available for the transport of amino acids in this system.

Equilibrium and steady-state models of the coupling between the amino acid gradient and the sodium electrochemical gradient in mouse ascites- tumour cells.

1. The tumour cells were incubated at 37 degrees C in Ringer solutions containing glucose, 1 mM-methionine, various concentrations of Na+ and K+ and, in some instances, ouabain or valinomycin to lower the membrane potential generated by the Na+ pump. After about 30 min, when the system had reached a steady state, the ratio [extracellular Na+]/[cellular Na+] varied from about 0.6 to 3.2 with the ionic conditions. The membrane potential, determined by means of the fluorescent probe 3,3'-dipropyloxadicarbocyanine, also varied systemically from about zero to--55mV.2. the ratio [cellular methionine]/[extra-cellular methionine] varied from about 1 to 35 in these circumstances. The Na+ electrochemical gradient, measured in the same units, varied from about 1 to 30. Its magnitude in 46 assays was almost directly proportional to, though slightly smaller than, the methionine gradient. 3. A mathematical model was used to define the relation between these two gradients, which were not in equilibrium, owing to the presence of a leak pathway for the amino acid. On the assumption that the values of [cellular Na+] were correct, the methionine gradient was about 1.8 times larger than this version of the gradient hypothesis predicted.

Brain amines and convulsions in four strains of parathyroidectomized, pinealectomized rat.

The tendency for four strains of parathyroidectomized (PTx) rats to convulse after pinealectomy (Px) was observed in this experiment; telencephalic serotonin, norepinephrine, and dopamine were examined to note any correlation between amines and convulsions. The strains of rats tested were Sprague-Dawley, Wistar, Long-Evans, and ACI. Duration to onset of convulsions was shortest in the PTx + Px Long-Evans. No convulsions were noted in the PTx +Px ACI strain, but at least 70% of the animals in each of the other PTx + Px groups did convulse. The administration of calcium gluconate (70 mg/kg) intraperitoneally in saline did not alleviate convulsions in the PTx + PTx Sprague-Dawley. Telencephalic serotonin was lowered in the PTx +Px Wistar while norepinephrine was depressed in the PTx + Px Long-Evans rat. Dopamine levels did not change. Previous work in the PTx +Px induced convulsion has led to the implication of norephinephrine alone, but this work indicates serotonin may be involved in some strains. The need for further study of the genesis of convulsions in the PTx + Px rat is clearly indicated.

The effects of ionophores on the fluorescence of the cation 3,3'-dipropyloxadicarbocyanine in the presence of pigeon erythrocytes, erythrocyte 'ghosts' or liposomes.

1. Pigeon erythrocytes, resealed lysed erythrocytes or liposomes derived from erythrocyte lipids were suspended in solutions containing up to 2 micrometer-3,3'-dipropyloxadicarbocyanine iodide. Gramicidin, valinomycin, nigericin or carbonyl cyanide p-trifluoromethoxy-phenylhydrazone, or combinations of these, were used to induce electrical diffusion potentials dependent on Na+, K+ or protons. In each instance hyperpolarization of the cell membrane lowered the fluorescence of the cell suspension, a process that was completed in about 1 min. Subsequent depolarization caused an increase in fluorescence. 2. Quenching of the fluorescence of the cell suspension appeared to be due to the reversible binding of the dye to the cells. Much larger amounts of dye were bound, both to the intact and to the resealed erythrocytes, than would be expected if partitioning of the dye cation followed the Nernst equation. The dependence of the binding on the extracellular dye concentration was studied in the presence and absence of valinomycin. The results were consistent with the suggestion of Sims, Waggoner, Wang & Hoffman [(1974) Biochemistry 13, 3315-3330] that the dye was bound at both membrane surfaces and that, at low dye concentrations, hyperpolarizing the cells promoted dye binding at the inner membrane surface. 3. The applications of the technique are limited by the circumstance that the direct effect of the electric field on the uptake of the dye into the cells is amplified by a binding process that may be affected by other physiological variables.