Gene-Enzyme Relationships in Neurospora Invertase

A spontaneous, single-gene mutation responsible for a total lack of invertase activity in Neurospora crassa is described. The mutation is believed to lie in the structural gene for invertase, since an immunologically cross-reacting protein is made by the mutant strain. In addition, there was no evidence for a defect in regulation of invertase activity or synthesis by the following criteria. (i) The invertaseless condition was recessive in heterokaryons; (ii) no invertase inhibitor was found in mutant extracts by mixing experiments; and (iii) none of the several sugars able to induce activity in wild-type strains was able to induce activity in the mutant strain. It was also discovered that most of the wild-type enzyme (55 to 75%) cannot be washed free from the rapidly sedimenting cell debris. This finding provided additional support for the hypothesis that Neurospora invertase is located within or about the cell wall.     

Freeze-drying characteristics ofSaccharomyces cerevisiae andSaccharomyces carlsbergensis

The dispersal of yeast clumps to the unicellular state by certain sugars, does not increase the percentage survival after freeze-drying. Neither are those changes in cell-wall composition which occur upon ageing of the cell, and which are detectable by means of snail-gut enzymes, related to this cellular property. However, pre-treatment, with -mercaptoethanol, of a strain ofSaccharomyces carisbergensis increased the survival rate. This may be due to the reduction of certain sites in the cell wall. The oxygen consumption of yeast cultures before and after freeze-drying, agree with the hypothesis that low viabilities can arise from localized cellular damage which prevents cell reproduction by budding.     

Cardiac Monitoring in a Community Hospital—Analysis of 18 Months' Experience

Cardiac monitoring facilities have been present in teaching hospital centers for over five years. A substantial decrease in mortality has been observed in monitored patients with acute myocardial infarction. The community hospital system offers a challenge to effective monitoring since many physicians care for patients and often many kinds of therapy are used.After 18 months of operation mortality from myocardial infarction was only 16.6 percent in a community hospital monitoring unit where the majority of the emergency care and resuscitation was carried out by nurses. Vital to this success was the use of standing orders for nurses, requirement of privilege to practice within the monitoring facility and acceptance of the nurse as a therapist in emergency situations.Fourteen patients were successfully resuscitated and were later discharged from the hospital. Four of them had ventricular fibrillation from digitalis intoxication.Patients with shock and severe congestive heart failure continue to be a major unsolved clinical problem. The results indicate that the potentially viable patient with serious electrical disturbances can almost invariably be salvaged.     

Gammaphotography

The Anger scintillation camera greatly broadens the range of studies performed by radioisotope imaging devices. Its ability to view in any direction, to make an image simultaneously of an entire field of view, and to obtain images rapidly, all serve to make scintiphotography analogous to fluoroscopy. Illustrations of its uses in static and dynamic gammaphotography and in numerical data processing are described.     

Medicine in Society—Part I: Change and Challenge

The Committee to Study the Role of Medicine of the California Medical Education and Research Foundation (CMERF) is grateful to Dr. Watts for the following paper which served as the philosophical basis for the Committee''s study and discussions. The Committee is also grateful to CMERF and to its president, James C. Doyle, for the encouragement and cooperation it has received in the course of its intensive study of a problem which is of great interest and concern to the medical profession of California.Dr. Watts'' background paper has served as a potent stimulus in directing the Committee''s attention to the continuing dialogue between medicine and society, and in focussing on problems and issues which will be the subject of the Committee''s Second Progress Report, excerpts from which are scheduled for publication in the next issue of California Medicine.     

The metabolism of the isomeric decalones

1. The metabolism of (+/-)-cis-1-, (+/-)-trans-1-, (+/-)-cis-2- and (+/-)-trans-2-decalone in the rabbit has been investigated. 2. (+/-)-cis-2- and (+/-)-trans-2-Decalone were both reduced to racemic secondary alcohols, conformationally related to the ketones administered, and possessing an equatorial hydroxyl group. These alcohols were excreted in the urine as glucuronides in amounts equal to about half the dose administered. The glucuronides were isolated both as triacetyl methyl esters and as sodium salts. The ester obtained after feeding with (+/-)-cis-2-decalone proved to be methyl (cis-cis-2-decalyl tri-O-acetyl-beta-d-glucosid)uronate, whereas (+/-)-trans-2-decalone yielded methyl (trans-cis-2-decalyl tri-O-acetyl-beta-d-glucosid)uronate. The sodium salts were shown to be sodium (cis-cis-2-decalyl glucosid)uronate and sodium (trans-cis-2-decalyl glucosid)uronate. 3. Enzyme hydrolysis of the sodium salts and acid hydrolysis of the esters derived from (+/-)-cis-2-decalone yielded (+/-)-cis-cis-2-decalol, and of those from (+/-)-trans-2-decalone yielded (+/-)-trans-cis-2-decalol. 4. (+/-)-cis-1-Decalone was reduced mainly to (-)-cis-cis-1-decalol and excreted as [(-)-cis-cis-1-decalyl glucosid]-uronic acid. A small amount of the corresponding (+)-isomer was produced, yielding [(+)-cis-cis-1-decalyl glucosid]uronic acid on isolation. Enzyme hydrolysis of these compounds gave the corresponding aglycones; both alcohols possessed an equatorial hydroxyl group. 5. (+/-)-trans-1-Decalone was reduced to (+)-trans-trans-1-decalol, with an equatorial hydroxyl group, and in smaller amount to (+)-trans-cis-1-decalol possessing an axial group. The former alcohol was excreted as [(+)-trans-cis-1-decalyl glucosid]uronic acid, and the latter as [(+)-trans-cis-1-decalyl glucosid]uronic acid. 6. From a knowledge of the conformations, and in some cases the absolute configurations, of the compounds administered and excreted, and by making the assumption that the coenzyme concerned in the reductions is NADH (or NADPH), an explanation of the above findings in terms of steric hindrance and thermodynamic stability is given.     

Microbiological Standards and Handling Codes for Chilled and Frozen Foods. A Review

The usefulness of microbiological standards for frozen foods is now a controversy in the trade and scientific literature. Most reviewers have given arguments both for and against, and have concluded that they should be applied with great caution. Such standards have the advantage of putting questions of safety on a convenient numerical basis. Canadian workers have reported that promulgation of standards has invariably raised the hygienic level of the products controlled.

Bacteriological standards have often been associated with the question of safety to the consumer. Everyone recognizes that food poisoning bacteria are a potential danger in any food. But many have argued that the history of food poisoning outbreaks from frozen foods is excellent and that there is no need for standards; on the other hand, proponents of standards have pointed to the incomplete investigation and reporting of outbreaks, and have argued that there may be more outbreaks than we realize. They have pointed to laboratory studies that have shown grossly mishandled precooked frozen foods to be truly dangerous. Some have proposed that pathogens should be absent from foods; but others have questioned that a microbiological standard can accomplish this end. Some pathogens, such as Salmonella or Staphylococcus have been shown to be so ubiquitous that their presence in some commercial foods is unavoidable. Also, sampling and analytical methods have been described as inadequate to guarantee that pathogens present will be detected. Some have argued that control at the source is a better way—through inspections of the plant operation, by enforcement of handling codes, or by processing procedures such as pasteurization, which would be more certain to result in a pathogen-free food.

A most important part of any of the proposed standards is a “total count” of viable aerobic bacteria. English workers have found that foods causing poisoning outbreaks usually had total viable counts above 10 million per gram. On the other hand, these same workers found Salmonella on meats with very low total viable count. The assumption by many that low total count indicates safety has been shown to be not always true. Furthermore, high counts of nonpathogenic organisms, such as psychrophilic saprophytes would have no public health significance.

The relation between bacterial level and quality is open to less controversy. Some authorities have pointed to bacterial level as a measure of sanitation, adequacy of refrigeration, or speed of handling. Others have indicated that to determine which of these factors caused a high count would be impossible with only a total count on the product as a guide. Some investigators have said a high count affects flavor adversely before actual spoilage is evident, and this may be a factor in competition on today's market. It is well established that initial bacterial level will affect the shelf-life of a chilled product. Methods of analysis are more nearly adequate for counts than for pathogens, but they need improvement, and should be clearly specified as part of any bacteriological standard. Foods with high count could sometimes be brought into compliance merely by storing them for a sufficient period frozen, or by heating them slightly. This has been cited by some authors as a disadvantage of bacteriological standards.

The enterococci and the coliform group (except Escherichia coli) have been shown to be ubiquitous and therefore should not be used alone to indicate fecal contamination. Although E. coli has greater significance, its source should be determined each time it is found.

Various reviewers have expressed the need for caution in the application of standards. The principal precautionary arguments we have found are as follows:

1) A single set of microbiological standards should not be applied to foods as a miscellaneous group, such as “frozen foods” or “precooked foods.”

2) Microbiological standards should be applied first to the more hazardous types of foods on an individual basis, after sufficient data are accumulated on expected bacterial levels, with consideration of variations in composition, processing procedures, and time of frozen storage.

3) When standards are chosen, there should be a definite relation between the standard and the hazard against which it is meant to protect the public.

4) Methods of sampling and analysis should be carefully studied for reliability and reproducibility among laboratories, and chosen methods should be specified in detail as part of the standard.

5) Tolerances should be included in the standard to account for inaccuracies of sampling and analysis.

6) At first, the standard should be applied on a tentative basis to allow for voluntary compliance before becoming a strictly enforced regulation.

7) Microbiological standards will be expensive to enforce.

8) If standards are unwisely chosen they will not stand in courts of law.

     

Improved Temperature-Gradient Incubator and the Maximal Growth Temperature and Heat Resistance of Salmonella

An improved all-metal temperature-gradient incubator produces its gradient by means of a bar permanently installed in a near-vertical position with its lower end in a cool constant-temperature water bath and with thermostatically controlled heaters near its top. Bolts hold the incubator in contact with the temperature-gradient bar, and polyurethane foam insulates the entire assemblage during use. Maximal growth temperatures of 34 representative strains of Salmonella were found to be between 43.2 and 46.2 C. In an agar medium with an initial level of 10⁶ cells per milliliter, no strain survived 50 C for 48 hr. S. senftenberg 775W showed no greater heat resistance at or near 48 C than did other species or other S. senftenberg strains. However, it was considerably more resistant than other strains at 55 C.