PubMed Health⌕ Search

Biomedical subjects

J M Kramer

Publications and source records attributed to J M Kramer.

100 records · Page 6Linked to original sources
PubMed1980

Quantitation of mRNAs during mouse spermatogenesis: protamine-like histone and phosphoglycerate kinase-2 mRNAs increase after meiosis.

Total RNA, prepared from immature or mature mouse testes or from spermatogenic cells separated on the basis of sedimentation velocity, was translated in vitro. Mouse protamine-like histone could be identified as an in vitro translational product when [3H]arginine was used as the label. The mRNA for protamine-like histone was detected only after meiosis; the appearance of a peak of radioactivity comigrating with protamine-like histone occurred only when RNA from mature testes or late spermatid cell fractions was translated. Phosphoglycerate kinase-2 (ATP:3-phospho-D-glycerate I-phosphotransferase, EC 2.7.2.3) was identified as an in vitro translational product by affinity chromatography followed by two-dimensional gel electrophoresis or by specific immunoprecipitation when [35S]methionine was the label. The mRNA for phosphoglycerate kinase-2 was detected only in mature testes or late spermatid cell fractions. These translational assays for protamine-like histone and phosphoglycerate kinase-2 mRNAs suggest that these messages are transcribed after meiosis.

Animals↗
PubMed1979

Purification and characterization of mouse glucose 6-phosphate dehydrogenase.

Glucose-6-phosphate dehydrogenase was purified to homogeneity from testes and kidneys of the inbred strain of mice (DBA/2J) by a simple two-step affinity column procedure. This involved the sequential application of 8-(6-aminohexyl)-amino-AMP- and -2', 5'-ADP-Sepharose columns and biospecific elution with NADP+ in both steps. The molecular and biochemical properties of the purified enzyme were studied in detail. These include the molecular weight determination, amino acid composition, steady-state kinetics, inactivation by high temperature, urea and iodoacetate, and immunology. The purified enzyme from mouse kidneys or testes was shown to be a tetramer with a molecular weight of 220,000. The enzyme is highly specific for glucose-6-phosphate, exhibits almost no activity with NAD+ as a coenzyme and is little inhibited by AMP or ATP. Michaelis constants for glucose-6-phosphate and NADP+ were determined to be 50 microM and 10 microM respectively. NADPH is a competitive inhibitor of NADP+ and has a Ki of 18 microM. Rabbit antisera against glucose-6-phosphate dehydrogenase were raised. The antisera also cross-react with the same enzyme from human and guinea pig.

Amino Acids↗
PubMed1979

Properties and production characteristics of vomiting, diarrheal, and necrotizing toxins of Bacillus cereus.

Evidence is provided that the enterotoxin of Bacillus cereus variously described in the literature as diarrheagenic toxin, diarrheal agent, fluid accumulation factor, vascular permeability factor, dermonecrotic toxin, and intestinonecrotic toxin is a single relatively unstable protein of molecular weight approximately 50,000 and isoelectric point of the order of 4.9. It is presumed to be the enterotoxin responsible for the diarrheal-type B. cereus food poisoning syndrome and it may also be the pyogenic and pyrogenic factor in nongastrointestinal B. cereus infections of man and animals. The enterotoxin is a vegetative growth metabolite produced to one degree or another by almost all B. cereus strains and is readily separated from phospholipase and heat-labile cereolysin but less readily differentiated from a heat-stable hemolysin. It is lethal to mice but may also be separable from another mouse lethal factor by electrofocusing. The emetic toxin responsible for the vomiting-type B. cereus food poisoning syndrome is clearly distinguishable from the diarrheal and other toxic factors and appears to be a highly stable compound of molecular size less than 5000.

Animals↗
PubMed1979

Severe clinical conditions associated with Bacillus cereus and the apparent involvement of exotoxins.

Twenty-one cases of infection with Bacillus cereus are summarised. The histories supplied showed that at least 15 of these were associated with severe or potentially severe symptoms including two deaths. Analysis of the production of exotoxins, including haemolysin and phospholipase, by these strains is given, and the relevance of these metabolites to the severity of the condition is discussed. Three incidents of bovine mastitis resulting from B. cereus and involving three deaths are also included. The observations presented here together with those of previous reports which are reviewed indicate that B. cereus may be of clinical importance, not just an opportunist but also as an agent of potentially severe infections in its own right.

Bacillus cereus↗
PubMed1978

Enumeration of micro-organisms in food: a comparative study of five methods.

Five methods for the enumeration of micro-organisms in food (pour plate, surface spread plate, surface drop, agar droplet, and microdilution) were used in parallel to examine 100 samples selected from a wide range of food products. Statistical analyses of the results showed that the regression and correlation coefficients between the methods were highly significant; the lowest correlation coefficient derived for any pair of methods was 0.979. A variation in count between the methods of less than 0.5 log10 cycles was given by 98% of the samples. Analysis of the operation times and material requirements of each method showed that substantial savings in cost, time, space and support labour were achieved with the microdilution and agar droplet techniques as compared with the conventional pour plate and spread plate methods.

Food Contamination↗
PubMed1978

A comparison of procedures to determine free fatty acids in rat heart.

The level of free fatty acids in intact tissues has been found to be low but is known to rise in proportion to the extent of autolysis. Therefore, the high levels of free fatty acid reported in the cardiac lipids of rats fed rapeseed oil were reinvestigated using two different procedures for homogenization. Quick freezing and pulverization at dry ice temperature followed by lipid extraction was found to give lower values of free fatty acids (200 microgram/g of wet heart tissue) than the more commonly used technique of employing rotating blade-type homogenizers (greater than 1700 microgram/g of wet heart tissue). The amount of diglycerides was found to be 3 times greater when the latter method was used. The high levels of free fatty acid and diglyceride suggest that extensive autolysis occurs during homogenization with a rotating blade-type homogenizer. Freezing and pulverization at dry ice temperature is therefore recommended for determining intact lipid classes in rat heart.

Animals↗
PubMedDate not supplied

Central line occlusion with three-in-one nutrition admixtures administered at home.

The use of single-container parenteral nutrition admixtures can be cost effective and can simplify home administration. Three-in-one admixtures (dextrose, amino acids, lipid emulsion, and other additives in a single bag) were in use when a marked increase in catheter occlusions was seen in the pediatric home parenteral nutrition population. Insoluble laminar deposits were found in the removed catheters. In all subsequently placed catheters, separate (SPLIT) infusions of lipid and parenteral nutrition solution were used rather than three-in-one admixtures. This was associated with an obvious decrease in catheter occlusions. Catheter life-span was retrospectively determined for 15 catheters of identical size and style that were used in eight patients who had received either infusions of three-in-one admixtures or SPLIT infusions. Life table survival analysis revealed a median survival time of 70 days for the three-in-one group (n = 8) and 290 days for the SPLIT group (n = 7). Survival distributions for the two groups were significantly different (p = .025). During the period of clustered catheter occlusion, the use of three-in-one admixtures that were stored in the home for up to 7 days was associated with a shortened catheter life-span. Occlusion or deposit development was not seen in catheters used for inpatient parenteral nutrition support when admixtures were prepared and infused within 28 hours. Catheter deposits were implicated as sanctuary sites for pathogenic bacteria in two patients. Failure to retrieve and inspect occluded catheters delayed the identification of the deposits.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Central Venous↗
PubMedDate not supplied

Neural control of the cardiovascular system during exercise. An integrative role for the vestibular system.

Precise regulatory signals are required in order to adjust the cardiovascular and respiratory systems to meet the demands of exercise. Two neural mechanisms, central command and a reflex originating in contracting muscles, are known to play a large role in exercise-associated adjustments in cardiovascular and respiratory activity. The extent to which other regulatory reflexes, such as vestibulo-autonomic reflexes, are able to impact upon the cardiovascular and respiratory systems during exercise is largely unknown. Further, brain regions that may integrate these control mechanisms are only starting to be investigated. We propose that medullary brain nuclei may integrate both exercise and vestibular signals to produce a more coordinated, and therefore efficient, means of adaptation to exercise in a gravitational environment.

Cardiovascular Physiological Phenomena↗