Marvin M. Nachlas

The determination of lactic dehydrogenase with a tetrazolium salt

Abstract A colorimetric method for the measurement of lactic dehydrogenase activity has been described, utilizing phenazine methosulfate as an intermediate agent for electron transfer from DPNH to a tetrazolium salt (INT). The use of gelatin to keep the formazan in colloidal suspension provided the added advantage of improving electron transfer via a phenazine methosulfate gelatin complex over that obtained with soluble diaphorase or phenazine methosulfate alone. Several compounds were studied for their ability to act as intermediate electron-transfer reagents, but none were superior to phenazine methosulfate. The sensitivity of the new method is comparable to others measuring either DPNH or pyruvate; its advantages are those of brevity and simplicity. Normal human sera were found to contain from 50 to 100 units of lactic dehydrogenase. The importance of avoiding hemolysis of the blood has been re-emphasized, and the possibility has been demonstrated that a 10–15% overestimation may occur due to hemolysis even when gross hemolysis cannot be recognized.

An evaluation of aminopeptidase specificity with seven chromogenic substrates

Abstract Seven chromogenic substrates were used to establish the identity of the classical leucine aminopeptidase. These substrates were the leucyl, glycyl, alanyl, phenylalanyl, methionyl, glutamyl, and arginyl amides of 2-naphthylamine. The cleavage of these substrates was studied by the enzyme (or enzymes) in four organs of the rat, and in the livers of five species. The rate constants, pH optima, influence of temperature, aging and fixation effects, and activities with substrate combinations were determined. Substrate hydrolysis by a purified preparation of leucine aminopeptidase was measured also. The currently available information would seem to favor the nonspecificity of aminopeptidase, with the likelihood that more than one aminopeptidase exists. Even though certain peptides may be preferentially hydrolyzed, there is so much overlap that the characterization of the specific aminopeptidase by its amino acid preference serves no more useful function than to label the substrate used. Therefore it is unrealistic to characterize the enzyme by the amino acid used, if a more specific implication is intended.

Closed-chest cardiac resuscitation in patients with acute myocardial infarction☆

Abstract An experience with 60 patients who sustained cardiac arrest while convalescing from acute myocardial infarction has been described. Nearly one half of these patients were under 65 years of age, and recovering from their first coronary artery occlusion. Eighty-three per cent of the patients sustained their arrest within the first 5 days of hospitalization. In 38 of the 60 patients, some warning of the impending event occurred in the form of recurrent chest pain, cardiac arrhythmias, or hypotension, whereas in 22 patients no premonitory symptoms or signs were noted. The cardiac arrests presented as ventricular fibrillation in 58 per cent, ventricular standstill in 22 per cent, and some other arrhythmia in 20 per cent. Although cardiac action was restored in 47 patients, 26 of whom had sinus rhythm, only 13 patients were restored to their pre-arrest status and only 3 were discharged from the hospital. From observations made during these attempts at resuscitation, several conclusions appear justified: (1) All patients with acute myocardial infarction should be placed in a coronary-care unit, with continuous electronic monitoring for at least 5 days. (2) When cardiac arrest is recognized, immediate attention should be given to the artificial circulation. External cardiac massage should be performed continuously and with sufficient vigor by a house officer or nurse until the automatic pneumatic pump can be substituted. A rate of 40 compressions per minute is desirable, and should not be interrupted. (3) As soon as the artificial circulation has been instituted, mouth-to-mouth or mouth-to-airway ventilation should be started. Insufflation of the lungs can be achieved by this method between every other sternal compression. The change-over to endotracheal intubation and automatic respiration should be undertaken only when fully equipped and trained personnel are present. (4) Concern with the electrical characteristics of the arrhythmia should be demonstrated only at this point. Ventricular fibrillation is best treated by three countershocks, given at 1-second intervals. If the current derived from the lower voltage (350 or 450 volts) is not effective, no hesitancy should be displayed in switching to shocks of 750 volts. Ventricular standstill or other types of arrhythmia which do not yield an effective arterial pressure should be treated with intracardiac epinephrine. The standardization of the resuscitative technique in these broad terms is highly desirable. Unless thoroughly trained personnel are involved, it is not uncommon, under these stressful circumstances, for serious deviations in procedure to occur. The usual result is delay in the institution of artificial circulation. This loss of time, as well as that which results from failure to recognize immediately the onset of the arrest, is believed to be responsible for many unsuccessful resuscitations. The potential rate of success in treating these patients has not been approximated by us or by any other workers in this field. Such approximation will occur only after more knowledge is obtained about the correct details of the resuscitative procedure, and the proper use of adjunct measures to support the circulation during the recovery period.

Role of some structural features of subtrates on trypsin activity

Abstract Tryptic hydrolysis of 27 different amides of arginine was studied in an attempt to learn more about the specificity requirements of trypsin. Chain length is important for tryptic action, the optimal length being one which contains four amides (pentalysine) or three amides and one urethane (carbobenzoxy-triarginyl naphthyl amide). The electronic characteristics of the groups blocking the α-amino group of arginine appear to play a role in that the more negatively charged groups are hydrolyzed more readily by trypsin. The properties of the amine attached to the enzyme-sensitive bond also have an influence on tryptic action. Aromatic amides are much more susceptible than simple amides in dipeptide and tripeptide substrates. The three most active substrates, Nα-carbobenzoxydiglycyl-l-arginyl-2-naphthylamine, β-carboxyproprionyl-l-diarginyl-2-naphthylamide, and Nα-carbobenzoxy-l-triarginyl-2-naphthylamide, were found to be split more readily than Nα-benzoyl-l-arginine-2-naphthylamide (BANA) by factors of 220, 147, and 113, respectively. As little as 5 μg of added trypsin per milliliter of serum can be identified in serum. A smaller amount could not be measured in spite of a series of attempts to separate trypsin from the anti-trypsin present in serum.

A simple portable pneumatic pump for external cardiac massage

Abstract A portable pneumatic pump for external cardiac massage has been described. The apparatus is easy to operate, involving only three maneuvers, namely, opening the gas valve, connecting the hose to the gas source, and turning the rate regulator to the desired speed. A two-transistor rate circuit controls a small relay which energizes the solenoid of the valve. A small 30 volt battery powers the transistors while a larger lantern battery is used for the solenoid. The control circuit may be bypassed by means of a switching jack, and the solenoid valve controlled externally for synchronization of the R wave. The apparatus has maintained adequate circulation so that dogs in ventricular fibrillation for 30-minute periods were easily restored to good health by external countershock. Arterial pressures were recorded in 3 recently deceased persons. Further experimental and clinical studies are being conducted to elucidate those circulatory and respiratory factors which will make external cardiac massage most likely to succeed.

Clinical experiences with mechanized cardiac massage

Abstract The important requisites for a mechanical pump for external cardiac massage have been described and are incorporated in a unit which has been evaluated during the past two and a half years. This instrument is portable, weighs only 31 pounds and is powered by oxygen or any other gas source. The ambulance model differs from the hospital model in that the exhaust oxygen is collected in a reservoir and then used to ventilate the lungs. Also, this model does not contain the optional feature of performing synchronized massage, which may be indicated when resuscitation is performed in the hospital. Both models permit the effective performance of external cardiopulmonary resuscitation by one person without incurring fatigue. The pump has been applied to many persons who sustained cardiac arrest. It produced adequate artificial circulation in each instance as manifested by a palpable peripheral pulse, a decrease in the size of the pupils, and the allowance of electrical conversion of ventricular fibrillation to a conducted beat. The most favorable cardiorespiratory factors appear to be a rate of 40 compressions/min., with a duration of systole one-third the cycle time, and with artificial ventilation being instituted between every other compression. It is most important that the artificial circulation not be interrupted for ventilatory or any other reasons. Clinical evidence could not be obtained to indicate that faster massage rates were better. Since the mechanical pump was never found to be less effective or more traumatic than manual massage, the many obvious advantages of mechanization warrant the substitution of the pump for the individual massager as soon as it is brought to the treatment area. The ultimate rate of salvage possible among patients sustaining cardiac arrest outside the operating room is not known. The solution of several questions currently apparent will undoubtedly influence the results; e.g., (1) should open-chest massage be used when the closed method appears unsuccessful, and when should it be instituted, (2) is it necessary to synchronize mechanical compression with electrical systole, and (3) is any advantage to be obtained by using adjunct supportive measures such as balloon occlusion of the abdominal aorta and internal diastolic pumping?

Clinical features relevant to possible resuscitation in death after acute myocardial infarction

Abstract The clinical course of 138 patients who died after an acute myocardial infarction have been reviewed, with the aim toward elucidating those features which might influence the possibility of resuscitation. The majority of the deaths occurred unexpectedly, presumably as the result of an acute arrhythmia. Failure of the heart to function adequately as a pump was noted in 44 per cent—three fifths of these patients died from congestive heart failure, and two fifths from circulatory collapse. Seventy-four per cent of the deaths occurred within a 5-day period of hospitalization. The sex, age, and presence of previous cardiac disease showed no association with the manner of dying. Patients over 70 years of age did not die more frequently in shock, but did die from congestive heart failure slightly more often than expected. Even when the past history was positive for previous heart failure or infarction, the likelihood of death occurring in heart failure was not increased. The physical findings on admission revealed that 40 patients were in shock and 59 had some degree of congestive heart failure. These abnormalities had a striking effect on the mode of death, in that shock remained a prominent feature of the illness in the former group, whereas in the latter group the incidence of failure deaths was much greater than expected. The finding of ventricular irritability was associated with a rhythm death in 79 per cent of the cases. Electrocardiograms revealed no evidence of myocardial irritability in 63 patients, and no conduction abnormalities in 86. Nevertheless, over one half of these patients also died from an arrhythmia.

Variations in Reduction of Tetrazolium Salts by Dehydrogenase Systems.

Summary Electronegative groups attached to either the N-2 phenyl or the N-3 phenyl rings are important in determining the readiness of enzymatic transfer of electrons to tetrazolium salts. The magnitude of the effects exerted by nitro, chloro, or cyano moieties are not identical when different dehydrogenase systems are compared. Furthermore, differences noted between several tetrazolium salts in any one dehydrogenase system are not necessarily reproduced when biochemical and histochemical preparations are compared. Although the reasons for these differences are not immediately apparent, preliminary observations with the succinoxidase system suggest that some clarification may follow closer inspection of site of transfer to tetrazolium salts in the chain of electron transport. Figure

Irrationality in the management of breast cancer. I. The staging system

The historic development of breast cancer staging began early in the 20th century with the simple concept of early localized disease, spread to regional nodes, and the presence of distant metastases. This last group often was divided into patients with advanced but perhaps still curable locoregional disease and incurable patients with distant metastases. As increasing numbers of prognostic factors were recognized, efforts were made to incorporate them into the staging systems to combine patients with similar prognosis into the same stages. These attempts resulted in the development of four classifications, namely, the Columbia, Manchester, International, and American tumor‐node‐metastasis (TNM) staging systems. Although many benefits of staging were reported, the most important was that of permitting valid comparisons between different treatments and different institutions. Many success‐limiting factors were noticed during the developmental years, and even though the TNM system has been accepted, numerous speakers and authors present their staged data in a confusing and ambiguous manner. Recommendations are made that would permit clarification of presentations to general medical audiences along with recognizable statistical validity.

Electrocardiographic Patterns During Resuscitation After Experimentally Induced Ventricular Fibrillation

Continuous closed-chest massage (mechanized and manual) and ventilation with pure oxygen were performed for 15 and 30-minute periods, to maintain viability in 43 dogs with electrically induced ventricular fibrillation. External countershocks were applied and 32 of the animals lived more than 48 hours. The return of electrical and hemodynamic functions of the heart, as well as the function of the central nervous system, were graded arbitrarily to characterize recovery from poor to excellent. Electrocardiographic changes (lead II) were studied in detail and compared with the gross result of survival or death, and also with more quantitative characterization of recovery. When the initial electrocardiogram after defibrillation contained a P wave, the prognosis was most favorable. When the P wave was absent the amount of ST segment depression in the initial complex differentiated the better from the poorer results. During the first hour following defibrillation, a variety of arrhythmias was noted, as well as varying degrees of change in the R, T, and ST portions of the electrocardiogram. The most serious arrhythmias, in decreasing severity, were idioventricular rhythm, atrio-ventricular block, and multiple premature ventricular contractions. Recovery was poorest when multiple arrhythmias occurred. Changes in the voltage of the R and T waves could not be correlated with prognosis. However, more favorable recoveries were noted in animals without significant changes in the ST segment than in animals having ST segment depression greater than 4 mm.