Raphides with barbs and grooves in Xanthosoma sagittifolium (Araceae)

Raphides in petioles of Xanthosoma sagittifolium are needlelike crystals about 50 micrometers long. The rectangular cross sections have maximum dimensions of approximately 850 by 250 nanometers. The raphides have two distinct end structures. One end is narrow, acute, and tapered to a point; the other is broad, acute, and abruptly pointed. Barbs, about 750 angstroms long with tips oriented away from the narrow end, occur along the length of the raphide on ridges on either side of two longitudinal grooves. These grooves, located opposite each other, give the raphide cross section an H-shape.

Effect of osmolality and phosphate, 'tris', 'tes', 'mes', and 'hepes' hydrogen ion buffers on the motility of bull spermatozoa stored at 37 or 5 degreesC

Bull spermatozoa survived incubation, in unstoppered tubes at 5 and 37�C, better in solutions of 250 m-05molesJkg than in solutions of higher or lower osmolali-ties regardless of the concentrations of sodium chloride or citrate in the solutions relative to the concentrations of phosphate, Tris, TES, MES, or HEPES. When buffer solutions contributed 120 m-osmolesJkg to a total diluent strength of 250 m-osmolesJkg, the ranking from best to worst on the basis of survival of spermatozoa was: MES, HEPES, TES, Tris, and phosphate. Comparisons when 50 mM con-centrations of the buffers were used showed the same ranking except that HEPES was as good as.MES.

Duration of premeiotic deoxyribonucleic acid synthesis and the stages of prophase I in rabbit oocytes

To estimate the duration of oocyte DNA synthesis 36, 3-day-old female rabbits received 3, 6, 9, 12, 15, or 18 injections of tritiated thymidine (thy-(3)H) at hourly intervals. The ovaries, removed at 1, 10, or 20 days after the first injection, were radioautographed. Counts made of the number of silver grains associated with oocyte nuclei in meiotic Prophase I indicate that the duration of DNA synthesis is between 9 and 12 hr. To determine the length of the stages of meiotic Prophase I, a group of 2-3-day-old rabbits was given a single sub-cutaneous injection of thy-(3)H, and the ovaries were removed at hourly and/or daily intervals after treatment. The minimum duration of leptotene was 3 hr and the maximum duration probably was less than 8 hr. The maximum durations of zygotene, pachytene, and diplotene were estimated to be 44, 216, and 96 hr, respectively. The interval from the end of oogonial DNA synthesis to the beginning ofpremeiotic DNA synthesis (G(2) + Mitosis + G(1)) appeared to be less than 6 hr.

The Efficency of Radiation Detection by Photographic Films: State-of-the-Art and Methods of Improvement

The performance of photographic films as radiation detectors has rested at a state-of-the-art platean for some time. In terms of detective quantum efficiency (abbreviated DQE) this plateau is at about 1% for the best films, which 1% should be compared with 100% for an ideal photon counter. The physical causes for the 100-fold discrepancy between reality and ideal performance are examined in detail: incomplete light absorption; a small inefficiency in convertihg photons into photoelectrons; a large loss due to recombination. of electrons with holes; a small loss dictated by a four-atom threshold;. a small loss dictated by random grain position; a large loss from the use of a wide dispersion of grain sizes. These factors account quantitatively for substantially all of the discrepancy between reality and ideal performance. We show that the recombination loss is a necessity that must ordinarily be tolerated in order to secure a good shelf life for films. Part of the loss may be recouped by the well-known method of latensification. Films with a wide dispersion of grain sizes will have a higher DQE if the grains operate at a threshold of two processed photons instead of four. Latensification permits one to approach the two-atom threshold condition.

Studies of the suitability of preparations of ewe and cow milk for storing ram spermatozoa at 37, 5, and-79 degrees C

Ram semen was diluted in skim ewe or cow milk, and in preparations of the non-dialysable components of these resuspended in various synthetic diluents, and was then stored at 37, 5, or -79�C. There was little difference in the protective action of preparations from these two sources. The toxicity of fresh skim milk was reduced by heating at 92�C for 10 min, by the addition of 0�5 mg/ml of cysteine hydrochloride, or by the processes involved in dialysis and lyophilization of the milk solids. However, heat denatured the ewe milk more than the cow milk. The best method of preparing diluents from fresh skim milk was to add 0�5 mg/ml cysteine hydrochloride and then to heat. To remove the toxic factor in fresh cow milk, either heating or addition of cysteine was as effective as, or better than, a combination of both treatments. In the range 0�38-3�00% w/v, the optimum concentration of lyophilized, non-dialysable skim milk preparations added to synthetic diluents depended on their source (i.e. ewe or cow milk), the heat treatment before dialysis, and the measure of response.

Influence of diluents and processing times after ejaculation on the survival of deep-frozen ram spermatozoa

Samples of semen were cooled to 5�C over 2 hr and stored for 1� 5, 5� 0, or 16�7 hr prior to freezing. Best revival was obtained after the 16�7 �hr period.

Studies of the artificial insemination of sheep: The effects on fertility of diluting ram semen, stage of oestrus of the ewe at insemination, and injection of synthetic oxytocin

Ewes were artifically inseminated with semen diluted in skim milk. In the first experiment, with an insemination dose of 50 x 106 spermatozoa, 10-fold dilution of semen did not reduce the fertility of the diluted sample if it was reconcentrated by centrifugation to the same volume as the undiluted controls. However, three later experiments conducted under extensive pastoral conditions showed that dilution in milk lowered the fertility of semen, and reconcentration of the spermatozoa had no effect. Only 8.8% fertility followed the insemination of 50 x 106 spermatozoa in semen diluted 10-fold and stored at 5°C for approximately 36 hr. The administration of 50 or 200 mU of synthetic oxytocin to ewes at an early stage after insemination had no effect on fertility. The intensity of marking with the crayons carried by vasectomized teaser rams, thought to be a measure of the intensity of display of oestrus, was positively correlated with the fertility of ewes at insemination. The greater the consistency and opacity of the vaginal mucus at the time of insemination, the lower was the fertility of the ewe. The fertility of ewes was highest during approximately the first 12 hr of oestrus, and dropped progressively through the two subsequent 12 hr periods.

Subintimal dissection of the cornary arteries. A complication of selective coronary arteriography and the transfemoral percutaneous approach

Selective coronary arteriography is now the procedure of choice in the determination of the existence and the delineation of the extent of chronic obstructive coronary artery disease. Since Sones and Shirey's original description of this technique, variations in the procedure and the approach have evolved. More recently, the percutaneous transfemoral artery approach to selective coronary arteriography has gained increasing favor because of the ease of intubation of both coronary arteries, stability of the catheter once positioned in the coronary ostium, and the high quality of cinefluorography and direct serial radiography.

Because of the tapered-tip design and positrol feature, the depth to which the coronary artery can be cannulated, and the angle formed by the tip of the catheter and the intima of the vessel, the possibility of subintimal dissection of the coronary arteries as an inherent complication of this approach arises.

Two such cases of subintimal dissection of the left coronary artery are described with cinefluorographic documentation.

It is recommended that after cannulation of the coronary vessels the catheter be withdrawn several millimeters from the lumen of the vessel in order to avoid this complication of an otherwise valuable diagnostic approach to selective coronary arteriography.

The fertility of ewes injected with synthetic oxytocin following artificial insemination

In an experiment involving the artificial insemination of 246 Corriedale ewes with 0.1 m1 of undiluted ram semen, the intramuscular injection of 200 mU or 800 mU of synthetic oxytocin following insemination, either 0-14 or 14-24 hours after the start of oestrus, had no effect on fertility.

The occurrence of oestrus in ewes and the duration and detection of pregnancy in artificially inseminated ewes

In a flock of 256 Corriedale ewes at Mittagong, New South Wales, the mean length of the oestrous cycle in two successive years was 16.9 � 1.14 days, and the length of gestation was 150.7 � 2.28 days (mean � S.D.). The proportion of ewes observed in oestrus during two periods of the day is also reported. In these trials and in subsequent insemination trials (two with Corriedale ewes at Mittagong and one with Merino ewes at Mudgee) more ewes commenced oestrus per hour between 7.30 a.m. and 6.00 p.m. than during the remainder of the 24 hours. Returns to oestrus within 24 days of insemination, or scores of udder development 160 days after the last day of insemination, provided as good an index of the pregnancy rate as mothering lambs at birth.