A method of estimating phosphagen and some other phosphorus compounds in muscle tissue

278. Studies on ass's milk: Composition

The total solids of samples of ass's milk ranged from 7·80 to 9·10, the solids-not-fat from 7·14 to 8·50, and the fat from 0·54 to 0·71%.

The nitrogen distribution in ass's milk is: casein 39·5, albumin 35·0, globulin 2·7 and non-protein nitrogen 22·8% of the total nitrogen. Ass's milk contains: casein 0·70, albumin 0·62 and globulin 0·07%. The total protein content is 1·39%. Ass's milk is therefore characterized by a low casein, a low globulin and a high albumin content.

The non-protein nitrogen consists of amino nitrogen 8·1, urea nitrogen 24·3 and uric acid 0·7 mg./100 ml. of milk. The urea content is twice that present in cow's milk.

The mean chloride and lactose contents of the milk samples are 0·037 and 6·1% respectively.

The average calcium and phosphorus content of ass's milk are 0·081 and 0·059% respectively. Half the calcium is ionic, and half is in colloidal form.

The phosphorus distribution is: total acid soluble 84·0, acid soluble organic 38·5, easily hydrolysable ester 27·4, inorganic 46·0, and colloidal inorganic 23·0 % of the total phosphorus. The ratio of CaO: P2O5is 1:1. 46 % of the total phosphorus is in ester form; this is high when compared with only 12 % in cow's milk; most of the phosphoric ester forms soluble barium salts, which is a distinguishing feature of ass's milk.

The total sulphur content is 15·8 mg./100 ml.

The fat has a penetrating odour and is coloured orange-yellow. It has an iodine value of about 86, which is much higher than that for human milk fat. The Reichert (9·5) and Kirschner values (5·7) are low.

In general, the composition of ass's milk resembles that of human rather than of cow's milk.

Energy-rich phosphate compounds in bull semen: comparison of their metabolism with anaerobic heat production and impedance change frequency

1. The concentrations of nucleotides and other energy rich phosphate compounds in bull spermatozoa and bull semen were examined at different times during anaerobic incubation at 37 °C. The variations in the concentrations of these compounds were compared with sperm heat production and impedance change frequency during anaerobic incubation. 2. Immediately after collection there were 129 ± 14 p μ moles ATP , 120 ± 15.5 p μ moles ADP and 271 ± 22 p μ moles AMP + HR (in approximately equal quantities) per sperma­tozoon. (10 3 p μ moles x sperm density = μ moles/ml. semen.) The correlation between ATP and ADP concentration per spermatozoon and the percentage of live spermatozoa in the sample was 0.89, P < 0.05. 3. During the whole period of incubation, which lasted 120 to 430 min, the following changes in sperm nucleotide content took place; ( a ) ATP decreased; ( b ) ADP decreased; ( c ) labile-P decreased; ( d ) AMP + HR increased; ( e ) there was no inverse relationship between ATP and ADP . 4. During the first hour of incubation, when there was a sharp fall in heat production and impedance change frequency, there was no comparable decline in ATP , ADP , or labile-P. In one experiment there was a 55% increase in ATP during this period. 5. Contrary to recent reports, compounds which were not nucleotides but which contained highly labile phosphate groups were found in bull semen. Their concentration was about 250 p μ moles/spermatozoon, of which 50 p μ moles was creatine phosphate. The possibility that the rest was acetyl phosphate or 1, 3-diphosphoglycerate is discussed. 6. When the anaerobic heat production of bull semen fell to zero, which in these experiments we established was not due to exhaustion of fructose in the external medium but to the low pH, ≼5.5, of the seminal plasma, there were still significant amounts of nucleotides present in the spermatozoa.

Comparative studies of vertebrate and invertebrate pyruvate kinases

1. Electrophoretic patterns showed that among the vertebrates studied, L isozyme was present in rat and frog liver and also in rat kidney. 2. M2 is a frequent component in vertebrate tissues, giving support to the proposal that M2 is the ancestral form differentiating to other isozymes. 3. The above trend cannot simply apply to invertebrates. 4. Muscle pyruvate kinases from various animals were inhibited by the particular phosphagen present in their muscle. 5. The inhibition may have an important role in the regulation of glycolysis in muscle.