Laser temperature-jump, spectroscopic, and thermodynamic study of salt effects on duplex formation by dGCATGC

Salt effects on duplex formation by dGCATGC have been studied with spectroscopic, thermodynamic, and kinetic methods. Circular dichroism spectra indicate different salt conditions have little effect on the structures of the duplex and single strand. NMR chemical shifts indicate the structure of the duplex in 1 M NaCl is similar to that of the B-form determined previously in 0.5 M KCl [Nilges, M., Clore, G. M., Gronenborn, A. M., Brunger, A. T., Karplus, M., & Nilsson, L. (1987) Biochemistry 26, 3718-3733]. Optical melting experiments indicate the effect of Na+ concentration on melting temperature is similar to that expected for a polynucleotide with the same GC content. Laser temperature-jump experiments indicate the effect of Na+ concentration on the rate of duplex formation is much less than is observed for polynucleotides. The observations are consistent with expectations based on a counterion condensation model. This is surprising for a duplex with only 10 phosphates.

The degradation of different protein supplements in the rumen of steers and the effects of these supplements on carbohydrate digestion

1. Four steers with simple rumen and abomasal cannulas were given diets consisting of ground and pelleted alkali-treated straw, rolled barley and tapioca supplemented with urea (diet U) or containing single-cell protein (diet SCP), maize-gluten meal (diet MGM) or rapeseed meal (diet RSM) in place of some of the tapioca. The isoenergetic diets were given in a 4 x 4 Latin square design in eight feeds/d at 3-h intervals and provided sufficient metabolizable energy to support a growth rate of approximately 0.5 kg/d. Chromic oxide and polyethylene glycol were given as markers and appropriate samples taken from the rumen and abomasum. Flows (g/d) at the abomasum of organic matter and nitrogenous and carbohydrate constituents were calculated. 2. Rumen ammonia levels were similar with all three protein supplements at about 9 mmol/l, which was significantly lower (P less than 0.05) than that in animals on diet U (16 mmol/l). Rumen liquid outflow rates (/h) were 0.099, 0.139, 0.125 and 0.160 for diets U, SCP, MGM and RSM respectively; the difference between diet U and diet RSM was significant (P less than 0.05). Corresponding values for Cr2O3 outflow rates were 0.027, 0.032, 0.027 and 0.030/h respectively, which did not differ significantly from each other. 3. RNA, 35S and diaminopimelic acid (DAP) were used as microbial markers. Efficiencies of microbial-N (MN) synthesis, expressed as g MN/kg apparently digestible organic matter, truly digestible organic matter or carbohydrate fermented, were generally not significantly affected by the diet and averaged 29, 22 and 29 respectively based on mean RNA and 35S markers. Corresponding values derived from DAP of 22, 16 and 21 g MN/kg respectively were all significantly (P less than 0.001) lower. Using 35S as microbial marker, MN flows at the abomasum as a proportion of non-ammonia-nitrogen flow were 0.78, 0.64, 0.51 and 0.78 for diets U, SCP, MGM and RSM respectively. Derived true rumen degradability values (g/g intake) of the total dietary N were 0.91, 0.79, 0.69 and 0.90 for diets U, SCP, MGM and RSM respectively. Protein supplement degradabilities for single-cell protein, maize-gluten meal and rapeseed meal were 0.73, 0.51 and 0.98 respectively. 4. Mouth-to-abomasum digestibility coefficients of the main neutral-sugar components of dietary polysaccharides were 0.68, 0.63 and 0.61 for arabinose, xylose and cellulose-glucose on diet U.(ABSTRACT TRUNCATED AT 400 WORDS)

Affirmative action in medical education and its effect on Howard and Meharry: a study of the class of 1975

During the decade of the 1970s, affirmative action programs were introduced in US medical schools for the purpose of increasing the number of black and other minority medical students and of improving the medical care resources for black and other minority communities. Having for many years served as the main sources of black physicians in the US, Howard University College of Medicine and Meharry Medical College School of Medicine were also affected by affirmative action. No previous studies have compared the black graduates from Howard and Meharry with black and other minority graduates from the other US medical schools.The purpose of this study was to compare these medical school graduates in terms of actual choice of specialty, patient characteristics, practice location, and specialty board certification, using the graduating class of 1975. A greater proportion of black graduates from Howard and Meharry chose primary care specialties than did black graduates from other schools, though this difference was not statistically significant. Black graduates from Howard and Meharry had significantly greater proportions of black patients compared with black graduates from other schools, but the same proportion of Medicaid patients.Though not statistically significant, black graduates from Howard and Meharry were less likely to be found practicing in federally designated underserved areas. Black graduates from Meharry were significantly less likely to have achieved specialty board certification, compared with graduates from Howard or the other medical schools. These results illustrate the experience of Howard and Meharry during the era of affirmative action and generally support their critically important role in producing black physicians and enhancing medical care resources in the black community.

Are we training too many medical subspecialists?

As of 1983, 10% to 40% of cities with a population of 200,000 to 500,000 lacked a board-certified physician in one or more medical subspecialties, and many additional cities of this size had only one certified representative in many of the subspecialties. Somewhat smaller cities (population, 125,000 to 200,000) had far less complete coverage. Even when one includes board-certified internists who declared themselves subspecialists but lacked certification, there were many relatively large cities without complete coverage. Between now and 2000, an appreciable portion of the projected larger pool of board-certified subspecialists will be required to deal with a growing population and an increase in per capita demand for care. Others will locate in underserved or underserved cities, but our data suggest that even in 2000, many relatively large cities will have a deficit of most types of subspecialists.

The diffusion of magnetic resonance imaging scanners in a changing U.S. health care environment

Technological aspects and early clinical experiences are arousing great enthusiasm over magnetic resonance imaging (MRI). However, influences such as regulation, reimbursement, and increasing competition also are playing important roles in determining the diffusion of this new technology. Of these considerations, competition among providers seems the most important. Competition related to MRI is manifested as direct competition over MRI services, using MRI to improve a provider's strategic position and competition among specialties. In making decisions concerning MRI acquisition and operation, providers are drawing upon their experiences with computed tomography (CT) to help them determine when would be the best time for acquisition, how to decide whether acquisition is appropriate, and how best to acquire, operate, and market the technology.

General problems associated with the analysis of amino acids by automated ion-exchange chromatography

Some of the general problems commonly encountered with the analysis of amino acids have been described. These include problems associated with the preparation and storage of samples prior to analysis and those associated with the analytical stage itself. The effects on the accuracy of the determination of amino acids have been discussed, together with possible solutions to some of the problems.

The effects of different sources of nitrogen supplementation on the post ruminal flows of organic matter and different nitrogenous constituents in steers

Friesian steers, virtually protozoa free, were equipped with simple rumen and abomasal cannulas. They were given diets consisting of approximately equal proportions of ground, pelleted alkali treated straw and a rolled barley, tapioca mixture supplemented with urea + casein (UC), soybean meal (SBM), 'normal' white fishmeal (NDF) or white fishmeal designated as being of 'low' rumen degradability (LDF). The diets were isoenergetic (the protein sources replacing part of the tapioca) and they were given in amounts to supply sufficient metabolizable energy (ME) to support an average growth rate of 0.5 kg/d. Rumen degradable nitrogen (RDN): ME values were estimated to be 2.08, 1.40, 1.90 and 1.66 for diets UC, SBM, NDF and LDF respectively. RNA, alpha-epsilon-diaminopimelic acid and 35S (added as sulphate) were used as bacterial markers. Chromic oxide and polyethylene glycol (PEG) were given as flow markers and flows (g/24 h) at the abomasum of organic matter (OM) and nitrogenous constituents were calculated. Rumen volumes and ruminal liquid fractional outflow rates were measured using PEG. Samples of mixed rumen bacteria separated from strained rumen digesta from animals receiving diet UC contained significantly less DAP-N (0.322 g/kg DM) than those from animals receiving diets SBM, NDF or LDF (0.530 g/kg DM). Mean rumen volume (approximately 15 l) and liquid fractional outflow rates (approximately 0.105/h) were similar on all diets but there was appreciable variation between animals. The proportion of OM intake digested in the rumen was similar on all diets. The proportional contribution of bacterial-N to the total non-ammonia-N passing the abomasum based on mean values derived from DAP and 35S as markers was 0.57, 0.47, 0.39 and 0.31 for diets UC, SBM, NDF and LDF respectively. Corresponding values based on RNA were 0.71, 0.50, 0.48 and 0.35 respectively. Bacterial-N (RNA) flows at the abomasum were 31, 25, 26 and 20 g/d for diets UC, SBM, NDF and LDF respectively. Corresponding values for 35S and DAP were 26, 24, 21 and 18 g/d respectively. Values derived from RNA flows were consistently and significantly higher (P less than 0.01) than those based on DAP or 35S. Mean estimated efficiencies of bacterial protein synthesis (g bacterial-N/kg OM truly digested) were 15, 15, 14 and 12 for diets UC, SBM, NDF and LDF respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of affirmative action in medical schools. A study of the class of 1975

In the early 1970s, affirmative-action programs were introduced to accomplish a number of social goals, including increasing the supply of minority physicians and improving the health care of the poor. To assess the success of such programs, we analyzed data on people who graduated from U.S. medical schools in 1975 to determine how specialty choice, practice locations, patient populations served, and board-certification rates differ between minority and nonminority graduates. A larger proportion of minority graduates (55 per cent vs. 41 per cent, P less than 0.001) chose the primary-care specialties of family practice, general internal medicine, general pediatrics, and obstetrics-gynecology. Significantly more minority physicians (12 per cent vs. 6 per cent, P less than 0.01) practiced in locations designated as health-manpower shortage areas by the federal government and had more Medicaid recipients in their patient populations (31 per cent for blacks, 24 per cent for Hispanics, 14 per cent for whites; P less than 0.001). Physicians from each racial or ethnic group served disproportionately more patients of their own racial or ethnic group (P less than 0.001), but minority physicians did not serve significantly more persons from other racial or ethnic minority groups than did nonminority physicians. Many minority physicians served patient populations much like those of their nonminority colleagues, which indicates that substantial integration of the medical marketplace has taken place. Significantly fewer minority graduates had become board-certified by 1984 (48 per cent vs. 80 per cent, P less than 0.001), and most of this disparity was associated with differences in premedical-school characteristics and in the patient populations they served. Our analysis shows that minority graduates of the medical school class of 1975 are fulfilling many of the objectives of affirmative-action programs.

Are fee-for-service costs increasing faster than HMO costs?

It is well known that the costs of care at health maintenance organizations (HMOs) at any point in time have been lower than in the fee-for-service sector, but how costs have changed in each of these sectors has been less well-documented. The only previous study, which examined the HMO experience during the 1960s and early 1970s, found that HMO and fee-for-service costs rose at approximately the same rate. The present study, which extends this analysis to the period 1976-1981, also demonstrates that HMO costs increased at a rate not detectably different from that in the fee-for-service sector. These results are consistent with the earlier conclusions that HMOs cause a once-and-for-all reduction in cost. They also indicate that the public has been willing to pay for much of the increased costs of modern medical technology. Key words: fee-for-service; health maintenance organizations; Rand Health Insurance Study; Group Health Cooperative data.

A note on estimation of food spoilage yeasts by measurement of adenosine triphosphate (ATP) after growth at various temperatures

The growth at 4 degrees, 10 degrees and 15 degrees C of six psychrotrophic yeasts isolated from foods was compared using total viable counts and ATP measurement. A linear relationship (r greater than or equal to 0.97) was obtained between log10 (number of viable yeasts) and log10 (ATP content) of cultures grown at these temperatures. This relationship was not temperature-dependent. The results are discussed and their significance for the rapid estimation of yeasts in foods is considered.

Is the teaching hospital an endangered species?

The nonmunicipal teaching hospital faces some special challenges in adapting to the increasingly austere fiscal environment in which all hospitals must operate. However, except in a few instances, such developments as constraints on Medicaid expenditures do not appear to be notably more serious for teaching hospitals than for their community counterparts. The teaching hospitals most closely connected with medical schools provide more charity care and carry more bad debt than community hospitals. But other teaching hospitals have about the same burden as their community counterparts. The most serious problem facing teaching hospitals results from new bases of prospective reimbursement, some of which do not adequately compensate hospitals that treat more "difficult" cases--that is, more expensive cases. Competitive providers of health care such as health maintenance organizations promise to reduce admissions at all types of hospitals; whether this reduction will selectively affect teaching hospitals is not yet clear. By contrast, the fiscal state of municipal teaching hospitals is far more precarious than that of their nonmunicipal counterparts. The ability of these institutions to maintain high-quality patient care and teaching programs is in considerable jeopardy.

Adoption and diffusion of a new imaging technology: a magnetic resonance imaging prospective

Adoption of magnetic resonance imaging (MRI) by individual purchasers and by the health care system will be influenced by many factors. A framework for considering these influences is offered, incorporating them into four major considerations: (1) MRI and its attributes--the technology, its safety and efficacy, and the benefits of acquisition; (2) communication channels--commercial and professional; (3) time for consideration of adoption and experiential testing; and (4) the medical system--including potential acquirers, health planning, and reimbursement. Among these, positive, negative, and variable influences affecting adoption can be identified. Factors that should most strongly motivate early adoption are the potential of the technology for providing new and useful clinical information and the competitive and economic benefits that early acquirers might enjoy. Important discouragements include the possibility of early obsolescence and that MRI represents an economic risk under diagnostic-related-group reimbursement. The less risky approach for most practices is to delay acquisition of MRI pending further experience with the technology and the changing reimbursement climate. Institutions that are primarily interested in the research potential of MRI or that are large enough to sustain the economic risks should consider earlier acquisition.

The simultaneous estimation of the amounts of protozoal, bacterial and dietary nitrogen entering the duodenum of steers

Four steers were given straw and tapioca diets, twice daily, in a 4 X 4 Latin-square design. These diets, containing 4.2 g nitrogen/kg dry matter (DM), were further supplemented with either urea, decorticated groundnut meal (DCGM), untreated (UT) casein or formaldehyde-treated (FT) casein to give a total of 19.7 g N/kg DM and 10.5 MJ/kg DM daily. Concurrent samples of rumen bacteria and protozoa and abomasal digesta were collected for each period of the experiment and the concentrations of 2-aminoethyl phosphonic acid (AEPA), diaminopimelic acid (DAPA), total nitrogen (TN), total phosphorus (TP), amino acids and hexosamines were determined in the dried preparations. The nature of the dietary supplements had little effect on the concentrations of most of these constituents or on the total protozoal numbers. Abomasal digesta samples marked with polyethylene glycol (PEG) and chromic oxide for flow estimation were collected over 24 h, and the proportions of protozoal-N, bacterial-N and microbial-N estimated simultaneously using the markers AEPA, DAPA and RNA respectively. These digesta-N components were also estimated using an amino acid profiling (AAP) method which gave, in addition, estimates of the dietary and endogenous components. For the diets containing casein, the proportion of dietary casein was estimated directly using casein-P as a marker. Estimates of the respective mean proportions of microbial-N in abomasal digesta non-ammonia-N (NAN) for the diets containing urea, DCGM, UT casein or FT casein were: AEPA 0.56, 0.32, 0.27 and 0.16; DAPA 0.88, 0.70, 0.81 and 0.57; RNA 0.98, 0.85, 0.92 and 0.53. Giving FT casein significantly (P less than 0.001) increased the flow of casein-N at the abomasum and a significantly (P less than 0.001) greater proportion of casein-N was found in abomasal NAN (0.51 v. 0.09) where FT rather than UT casein was given. The AAP method gave results for the proportions of microbial- and dietary-N (where casein was given) which were, in general, slightly lower than those obtained using RNA and casein-P as markers. Agreement with estimates of bacterial protein (from DAPA) and of protozoal protein (from AEPA) was less satisfactory. Comparisons of the various estimates of the proportions of microbial-N in abomasal digesta suggested that the results obtained for protozoal-N by AEPA were overestimates. AEPA was found in mixed rumen bacteria which may have accounted in part for these overestimates. However, AEPA was not detected in any of the dietary ingredients.

How many miles to the doctor?

We used detailed information from 16 states to determine the distance that residents of outlying areas (or of towns of less than 25,000, outside metropolitan areas) must travel to receive various types of medical care. For both 1970 and 1979, we found that approximately 80 per cent of such residents lived within 10 miles' driving distance of some physician and 98 per cent lived within 25 miles. Most of the remaining 2 per cent lived in areas so sparsely settled that physicians will not find them economically attractive as practice locations. During the 1970s, the distance of members of the studied population from medical and surgical specialists was substantially reduced. The greatest improvement occurred for the specialties that had the largest percentage increase in their numbers. As the physician pool expands further during the 1980s, geographic access to specialty care for rural and small-town residents should show a further notable improvement. However, this improvement may not suffice to meet what some consider the "medical need" of those who are geographically isolated or economically deprived.

Observations on the enumeration of moulds in food and feedingstuffs

This paper considers the technical problems associated with the quantitative analysis of mould in foods and feedingstuffs. It seeks to define a philosophy concerning the use of quantitative mycological data in advisory, investigatory and quality assurance situations and stresses the need for quantitative estimates always to be aligned with qualitative assessment of the mycoflora of foods and feedingstuffs.

Where have all the doctors gone?

As the supply of physicians grew during the 1970s, medical and surgical specialists diffused into smaller communities. In 1979, nearly every town with a population of more than 2,500 had ready access to a physician. The overall pattern of physician distribution was quite similar in the four disparate geographic regions chosen for study. The data strongly suggest that competitive forces play a major role in determining where physicians choose to practice. As the pool of physicians expands during the 1980s, a wide range of services will become increasingly available to populations outside metropolitan areas. The methods developed here provide important tool for evaluating and shaping health manpower policy.

Doctors' attitudes to health centres

In one Inner London health district many doctors seemed reluctant to work in health centres. To investigate the reasons, 44 general practitioners in two matched groups were interviewed. Those working in health centres appreciated the advantages of pleasant premises and the presence of a primary health care team. Other doctors believed health centres were disliked by patients, were bureaucratic in organization, and involved difficult interpersonal relationships. These were confirmed as real problems by health centre doctors. Thus, reluctance to join health centre practices is based on a realistic appraisal of the drawbacks. Recommendations are made.

The changing geographic distribution of board-certified physicians

We studied the recent distribution of board-certified specialists among cities and towns of different sizes. Between 1960 and 1977, diplomates of the eight specialty boards that we studied appeared for the first time in many small nonmetropolitan towns. The percentage increase in numbers of specialists in small towns significantly exceeded that in cities, but the absolute increase in specialists per 100,000 persons was greater in metropolitan areas. Our findings suggest that the increased supply of specialists activated market forces that caused the observed changes in distribution. It is also possible that a new preference for small-town living has contributed to this evolving pattern. If an increase in physician supply has been the major force responsible for the movement into nonmetropolitan areas, this trend implies that smaller and smaller towns will acquire board-certified specialists as the number of physicians increases.

The amino acid requirements of the preruminant calf

1. Ten calves (50--58 kg live weight) were given a diet consisting of diluted whole milk, wheat gluten and supplemented with appropriate nutrients including amino acids but deficient in lysine. The lysine reequirements of these calves, which were growing at approximately 0.25 kg/d, were estimated from responses to lysine supplementation of this diet. From plasma urea, plasma lysine, nitrogen retention and apparent digestibility of N responses the estimated lysine requirements were 8.5, 7.5, 7.2 and 7.6 g/d respectively. 2. From the mean lysine requirement (7.8 g/d) and the ratio, lysine: otheressential amino acids in carcasses of similar calves the estimated requirements were (g/d): methionine 2.1, cystine 1.6, threonine 4.9, valine 4.8, isoleucine 3.4, leucine 8.4, tyrosine 3.0, phenylalanine 4.4, histidine 3.0, arginine 8.5, tryptophan 1.0.

Nitrogen metabolism in calves. Effect of giving different amounts of dietary casein with and without formaldehyde treatment

I. Calves were given a basal diet of straw and flaked maize (12 g nitrogen/kg dry matter (DM)) or diets with some flaked maize replaced by untreated (UT) casein or formaldehyde-treated (FT) casein to give 19, 29 or 34 g N/kg DM. 2. At all intakes rumen ammonia concentrations were lower and amounts of total-N, non-ammonia-N and amino acid-N entering the duodenum were high when FT-rather the UT-casein supplements were given. 3. Direct measurement of casein entering the duodenum indicated that giving FT rather than UT casein led to much greater amounts of dietary casein escaping degradation in the rumen (70--90% compared to 10--20%). Calculated values for fermentable N indicated that with this low degradability diets containing FT-casein would have provided inadequate N for maximum microbial synthesis in the rumen, and this probably accounted for the marked reduction in amounts of non-casein-N entering the duodenum when FT rather than UT casein was given. 4. Amino acid patterns in duodenal digesta samples after giving the basal diet or diets containing UT-casein were similar. Giving diets containing FT-casein led to changes in this pattern which could sometimes, although not always, be accounted for by estimated differences in proportions of dietary and microbial proteins. 5. At the highest level of N intake FT-casein-supplemented diets led to significantly higher concentrations of most essential amino acids and lower concentrations of most non-essential amino acids in plasma than did UT-casein-supplemented diets. Plasma urea concentrations increased with increasing N intake but were not significantly different for UT- and FT-casein-supplemented diets.

Concentrations of amino acids and urea in the plasma of the preruminant calf and estimation of the amino acid requirements

1. A study was made of factors affecting the plasma concentrations of free amino acids (PAA) and urea (PU) in calves receiving liquid diets. 2. When calves were given whole milk (approximately 0-05 kg/kg live weight) at 10.00 and 17.00 hours there were marked decreases in PAA and slight decreases in PU for about 3-4 h after the morning feed. Both PAA and PU thereafter increased slightly and then remained constant for the next 10 h. In subsequent comparative experiments samples were taken 3 h after the morning feed. The variation in plasma methionine, isoleucine, leucine, phenylalanine, tyrosine and total PAA was apparently greater between than within animals. 3. In calves transferred from a diet of whole milk to one consisting of diluted whole milk supplemented with appropriate nutrients, including amino acids, but deficient in methionine, PU increased markedly and plasma methionine decreased. 4. Two calves (50-60 kg live weight) given the latter diet supplemented to give an intake of more than 4-5 g L-methionine/d together with 0-3 g cystine/d showed marked increases in plasma methionine. This was considered to correspond with the point at which methionine requirements were met and that under these conditions the methionine requirement for these calves (mean value plus or minus SE) was 4-5 plus or minus 0-2 g/d. In the same two calves PU decreased markedly with increasing levels of methionine supplementation up to 3-9 g/d and the estimated methionine requirement (mean value plus or minus SE) was 3-9 plus or minus 0-4 g/d.

Concentrations of amino acids and urea in the plasma of the ruminating calf and estimation of the amino acid requirements

1. A study was made of factors affecting the plasma concentrations of free amino acids (PAA) and urea (PU) in calves receiving approximately equal daily amounts of concentrates (flaked maize and protein supplements) and straw, the former at 10.00 and 17.00 hours, the latter at 17.00 hours only.

2. For calves receiving a diet containing 20 g nitrogen/kg dry matter in which the protein supplement was decorticated, extracted groundnut meal (DCGM) (diet A) there were marked increases in PAA and PU about 1–2 h after a morning feed, then a fall in these values 2 h later to a level which was maintained for the next 3 h. No similar changes occurred after the evening feed. Samples taken 3 h after the morning feed were used in subsequent comparative experiments. There was much more variation between animals than within animals in total PAA, PU and the concentrations of most individual amino acids in these samples.

3. Total PAA and most individual amino acid concentrations were not appreciably affected when the DCGM intake was reduced to give 10 g N/kg dry matter in the diet (diet C), but PU was halved. When maize gluten replaced DCGM as the protein supplement at the higher N intake (diet B) then PU doubled, but again total PAA and most individual amino acid concentrations were little affected. Exceptions were arginine, which was halved, and leucine, which was doubled.

4. Infusions of more than 4·4 g L-methionine/d into the abomasums of calves (110–160 kg live weight) receiving diet A led to a marked increase in plasma methionine concentration. This was considered to correspond with the point at which methionine requirements were met. Using a chromic oxide marker to estimate flows of methionine and cystine from the rumen to the duodenum, it was calculated that under these conditions the methionine requirement was 9·8 g/d, with a cystine flow of 4·9 g/d. Similar calculations showed the corresponding value to be 7·5 g/d with a cystine flow of 2·8 g/d for calves receiving diet C.

5. Infusion of increasing levels of L-lysine into the abomasums of calves (110–160 kg live weight) receiving diet B led to a progressive increase in plasma lysine concentration. There was no consistent change in the rate of increase with increasing amounts infused. Estimated lysine requirement appeared therefore to be less than the flow of lysine from the rumen to the duodenum under these conditions (18·8 g/d).

A collaborative study on the determination of tryptophan in feedingstuffs

The results are reported of collaborative work carried out at eight laboratories to assess the Miller1 and Spies and Chambers2 procedures for the determination of tryptophan in protein concentrates and gave values for groundnut, soya bean and cottonseed meals of 1.0, 1.4 and 1.2 g/16 g N, respectively. The results obtained by both methods were similar, though collaborators preferred the Miller method.