Some biological aspects of partial starvation. The effect of weight loss and regrowth on body composition in sheep

1. A study of the effects of four dietary treatments on body-weight and the water, protein, fat and energy content of the empty bodies of forty-three Suffolk ewes is reported. The treatments were as follows: T1,ad lib. food intake from a full-body-weight (FBW) of 40 kg to 71 kg; T2, partial fasting with a resulting weight loss from 71 kg to 50 kg FBW; T3, realimentation and regrowth from 50 kg to 71 kg FBW; T4, a slight food restriction producing a reduced growth rate from 40 kg to 50 kg FBW followed byad lib. food intake from 50 kg to 71 kg FBW. On all treatments sheep were slaughtered in groups of three at 7 kg intervals between 50 kg and 71 kg FBW.

2. The whole body, with the exception of several body organs and glands, wool and the contents of the gastrointestinal tract, was minced and analysed for water, protein, fat and energy. Adipose tissue samples were removed at slaughter from subcutaneous and internal fat depots for histological examination. Regression analysis was used in comparing treatment effects on body composition.

3. No significant differences were observed between the results of T1and T4. In consequence these results were pooled and are referred to as T1. At 40 kg FBW the empty (ingesta-free) bodies of the lambs contained approximately 52% water, 14 % protein and 29% fat. Through normal growth to 71 kg FBW on T1these values had changed to 40, 11.5 and 45 %, respectively. Following weight loss to 50 kg FBW on T2the water, protein and fat contents of the empty bodies were 47, 13.5 and 35 %, respectively. Regrowth on T3to 71 kg FBW resulted in little change in these components, the respective values being 46, 13 and 36 %. The sheep which had undergone weight loss and regrowth retained significantly more water and less energy than normally grown controls and tended to deposit less fat and more protein.

4. Gastrointestinal tract contents accounted for 11 % of FBW at 71 kg in T3animals. In T1, the value was 7.1 % at a similar FBW. Thus there was an average increase of over 56 % in contents in the realimented animals.

5. Mean adipocyte diameter at 50 kg FBW on T1was 134 ± 3 μm. At 71 kg FBW the mean diameter had increased to 152 ± 9 μm. Weight reduction (T2) and regrowth (T3) resulted in mean diameters of 122 ± 4 μm and 143 ± 4 μm at 50 kg and 71 kg FBW, respectively.

Molecular-weight estimates of milk-fat-globule-membrane protein-sodium dodecyl sulphate complexes by electrophoresis in gradient acrylamide gels

The molecular weights of milk-fat-globule-membrane proteins solubilized in sodium dodecyl sulphate were estimated by gradient gel electrophoresis. Standard curves were calibrated from both protein and glycoprotein markers of known molecular weight. Six major proteins were observed with Coomassie Blue staining and six with periodic acid-Schiff staining. The behaviour of the membrane proteins and the marker proteins was compared on several different single strength sodium dodecyl sulphate-polyacrylamide gels between 3 and 12% (w/v). The results were used to calculate the free electrophoretic mobility and retardation coefficient of each protein. Glycoprotein markers had a significantly lower mean free electrophoretic-mobility value than the protein markers. Three of the milk-fat-globule-membrane glycoproteins were shown to be independent of any of the Coomassie Blue-stained bands. On the basis of a comparison of the free electrophoretic-mobility and retardation- coefficient values of markers and unknown proteins the most appropriate standard curve for molecular-weight estimation was chosen.

Significance of perfusate lactic acidosis in cadaveric renal transplantation

Thirty-two human cadaver kidneys were assessed by continuous perfusion before transplantation. Altogether, 26 were transplanted. Ten kidneys functioned immediately, of which nine had excellent renal function at three months. Sixteen had delayed onset of function, of these only five had excellent function at three months. There was no difference in warm ischaemic interval between the two groups or in ice storage time. The immediate function group, however, were perfused for twice as long as the delayed function group. The two groups could not be separated on donor history, but they could be precisely separated during perfusion by measuring lactic acidosis and lactic acid dehydrogenase (LDH). The biggest single difference between the groups was in terms of donor preparation.

Proventriculus of a marine annelid: muscle preparation with the longest recorded sarcomere

EACH MUSCLE OF THE SYLLID (ANNELIDA: Polychaeta) proventriculus, the region of the gut posterior to the pharynx, contains a single zigzagging Z band, flanked on each side by a sequence of I-A-H-A-I bands defined by thick (60-90 nm) and thin (5 nm) filaments. The thick filaments show a 14-nm periodicity similar to paramyosin. The muscle cell terminates at the level of the outer I bands. The muscle does not include a complete sarcomere in the strict sense, as defined by a pair of Z bands, but the equivalent H-H distance reaches about 40 mum. Electrophysiological evidence suggests that contraction and relaxation of the cell are, respectively, associated with depolarizing and hyperpolarizing potentials.

Growth-hormone deficiency in iatrogenic hypothyroidism

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Neural Activation of the Heart of the Lobster Homarus Americanus

1. Glass microelectrodes were used to record intracellular activity from the striated muscle fibres of the heart of the lobster Homarus americanus.

2. In spontaneously beating hearts bursts of impulses are generated at regular intervals by neurones in the cardiac ganglion. These bursts produce depolarizations of the muscle fibres. Each depolarization is associated with a contraction of the heart. The depolarizations consist of many depolarizing steps; each step is related in a one-to-one manner to a nerve impulse and is believed to be an excitatory junction potential (EJP). The depolarizations (400-700 ms duration in different preparations) exhibit a fast rise to a peak (35-40 mV) followed by a plateau (20-25 mV) which decays to the resting level (51.5 ± 3.2 mV, n = 148).

3. Current-voltage curves indicate that the EJPs do not give rise to regenerative membrane responses.

4. Small, spontaneously produced potentials were recorded in the presence of TTX. Autocovariance tests show that the potentials occur independently and are likely to be miniature junction potentials.

5. Polyneuronal innervation of the muscle fibres was demonstrated by applying stimuli of gradually increasing intensity to the distal ends of cut nerves while recording the responses of a muscle fibre.

6. When a train of stimuli is applied at an intensity to evoke activity from a single axon, the first response of a muscle fibre is usually greater than the second; facilitation of the second and subsequent responses takes place. The degree of facilitation developed depends on the frequency of stimulation. Facilitation decays exponentially with a time constant of a few seconds.

7. In two-pulse experiments the second response was depressed when the interpulse intervals were ≤ 0.5 s.

8. Examples of combined facilitation and depression are presented.

The Dome fermentor: a versatile unit suitable for batch, continuous, and synchronous cultivation of microorganisms or tissue cells

An inexpensive but versatile and reliable fermentor of novel design is described which may be used for cultivating a wide range of microorganisms and tissue cells in batch, continuous (single and multistage), and phased (synchronous) culture. It can be used advantageously for growing material sensitive to the shearing effects of circulation pumps or impellers of other fermentors. The conditions of aeration are comparable with those observed in conventional fermentors.

Electrophysiological Studies on Initiation and Reversal of the Heart Beat in Ciona Intestinalis

1. Electrophysiological techniques have been used to define pacemaker characteristics and organization in the heart of the tunicate Ciona intestinalis. The frequency of spontaneous beat initiation was regular or irregular for a given period of time; in any single heart, these frequency modes intermittently changed from one to the other in no regular order. Reversals could take place immediately, after a pause, or after collisions.

2. Trains of electrical stimuli applied to the ends of the heart could drive propagated contractions at a frequency of up to 2.6/sec, and dominance could be controlled by altering the frequency and/or intensity of the stimuli. Each end gave a characteristic response to increasing frequency of driving, and the threshold for one-to-one driving was frequency-dependent.

3. When the middle of a heart was ligatured, the two ends were independently active. Visceral ends exhibited regularly varying levels of high and low frequency with a period of several minutes, whereas the frequency levels of the hypobranchial ends varied irregularly.

4. Intracellular resting potentials were approximately -50 mV., and propagated action potentials associated with contractile events did not show ‘overshoot.’ Partial electrical responses were affiliated with weak or failing mechanical events, and complex, double-peaked intracellular potentials were often associated with collisions. In some cases a cell could show electrical activity that was completely dissociated from the mechanical response of the whole heart. Excitation thus probably spreads passively between cells, and multiple foci of activity may co-exist at any given time.

5. From electrophysiological and anatomical data, an hypothesis is proposed to explain the observed mechanical activity on the basis of the interactions of individual cells and higher-order interactions among groups of cells.