Showing papers in "Reproduction in 1968"

Proposal for a classification of oocytes and follicles in the mouse ovary

Abstract: The need to develop a common terminology to describe the components of the ovary has been felt for some time (Gatz, 1955; Wischnitzer, 1966). A standard nomenclature would greatly facilitate the comparison of results relating to the development of the ovary and follicle growth under normal as well as experimental conditions. Various classifications have been used to describe stages of oocyte and follicle development. Some authors use the shape of the granulosa cells and the number of layers surrounding the oocyte as the main characteristic (Engle, 1927; Mandl & Zuckerman, 1950; Adams & Hertig, 1964; Hadek, 1965). Others take the largest diameter or the volume of the follicles as the distinguishing criterion (Boling, Blandau, Soderwall & Young, 1941; Paesi, 1949), while still others use a combination of the number of cell layers and follicle diameter to describe the stage of follicle development (Bullough, 1942; Ingram, 1959; Knigge & Leathem, 1956). Variations in the size of the oocyte in addition to the variation in size of the follicle has only rarely been taken into account to describe the follicle development (Mandl & Zuckerman, 1952; Peters & Borum, 1961; Brambell, 1956). Terms like primordial follicles, small follicles and primary follicles have been used to describe follicles with a single layer of cells attached to the oocytes. Secondary and growing follicles described follicles with several layers of cells surrounding the oocyte. Tertiary, large, vesicular, Graafian or preovulatory follicles are some of the terms used for various later stages of follicle growth. Clearly, a more accurate classification is needed to define the stages ofoocyte and follicle development. We would like to communicate a classification which has proved useful in evaluating and comparing changes in oocyte and follicle growth under different conditions. The classification is based on ( 1 ) the size of the oocyte in follicles of different stages of development, (2) on the size of the follicle defined by the number of cells constituting the follicular envelope, and (3) on the morphology of the follicle (Text-fig. 1).

Complete development in vitro of the pre-implantation stages of the mouse in a simple chemically defined medium

Abstract: Whitten (1956) showed that 8-cell mouse embryos develop into blastocysts in a simple chemically defined medium containing glucose, and McLaren & Biggers (1958) demonstrated that blastocysts cultured in this way produce normal mice when transferred into uteri of foster mothers. Whitten (1957) also showed that late 2-cell mouse embryos developed into blastocysts if lactate was incorporated in the medium but earlier stages did not cleave under these conditions. Thus the observation that mouse zygotes develop into normal blastocysts in the lumen of oviducts in organ cultures (Biggers, Gwatkin & Brinster, 1962) suggested that special conditions for initial development are provided by the tube. Recently, Whittingham & Biggers (1967) demonstrated that 1-cell embryos cleave to the 2-cell stage in a simple medium containing lactate and pyruvate (Brinster, 1965), and that these 2-cell stages develop into blastocysts in organ cultures of the ampullary region of the Fallopian tube. The unknown requirements provided by the Fallopian tube appeared to operate only in the intermitotic period between the first and second cleavage. In this paper we describe a simple chemically defined medium in which the eggs ofcertain hybrid mice develop from the 1-cell stage to the blastocyst completely in vitro. These blastocysts are capable of implantation and thus we have overcome the final barrier which prevented complete development in vitro of the pre-implantation stages of a mammal independent of the female genital tract. Eggs were obtained from F1, C57BL/10J\\m=x\\SJL/J females on the morning on which a copulation plug was observed after pairing with a BALB/cDg or F1 BALB/cDg\\m=x\\129/J male. The cumulus was completely removed by hyaluronidase in Dulbecco's phosphate-buffered saline (pH 7\\m=.\\2,440 U.S.P. units/ml), and the eggs were washed twice with the culture medium, inspected for pronuclei and polar bodies, and then cultured in 1 ml of medium in 5-ml plastic tubes using the method described by Biggers, Whitten & Whittingham (1968). The composition of the medium is presented in Table 1. One hundred and sixty-three 1-cell eggs from the hybrids were cultured in this manner and 122 apparently normal blastocysts, many of which were expanded, developed at the normal rate. Five viable offspring were obtained from eighteen of these blastocysts after they were transferred to uteri of foster mothers. In contrast, blastocysts were observed less frequently when eggs from

Aspects of reproduction in the alpaca

Abstract: Summary. The alpaca, Lama pacos, does not have regular oestrous cycles, but oestrus lasts for 21 to 36 days during the breeding season. Ovulation is induced by coitus. Follicular ovulation rupture occurs spontaneously 26 hr after coital stimulation and can be induced by a single injection of hcg. The low fertility observed in this species is considered to be due to low sperm production in the males and a high incidence of pseudopregnancy in the females. The gestation period has been determined to be about 342 to 345 days.

Developmental potential of single blastomeres of the rabbit egg

Abstract: Recently fertilized eggs of the mouse, rat and rabbit in which one or more of the blastomeres have been destroyed are capable of further development (Nicholas & Hall, 1942; Seidel, 1952, 1956, 1960; Tarkowski, 1959a, b; Mintz, 1962; Daniel & Takahashi, 1965). In most instances the single blasto¬ meres were either cultured in vitro for short periods or transferred to recipient females which were autopsied within a few days of transfer. On the rare occasions when recipients were allowed to survive to term, Seidel (1952, 1960) reported the birth of living young from two-cell rabbit eggs in which one of the blastomeres had been destroyed, and Tarkowski (1959a, b) reported live births in three mice which had received either twoor four-cell eggs in which one blastomere had been destroyed. Tarkowski & Wroblewska (1967) have recently presented a detailed account of the development of isolated blasto¬ meres of fourand eight-cell mouse eggs maintained under in vitro conditions for 36 to 48 hr.

Seasonal breeding of free-ranging rhesus monkeys and related ecological factors.

Abstract: The seasonal appearance of mating activities and births of rhesus monkeys in a free-ranging colony on two small islands near La Parguera, Puerto Rico, were recorded from the founding of the colony in 1962 to August 1966. Mating activities began in late August or September, reached a peak during November and December, and ceased in March or April. Except for a wide spread early in the colony's history, births were confined to the period from March to July, with 74% occurring during May and June. Lactating females began mating activities later than non-lactating females. The onset of mating typically followed vegetation changes associated with a period of high rainfall in late summer. The correlation between rainfall and mating activities, perhaps resulting from vegetational changes, also appears to be present at Cayo Santiago, another island colony of monkeys, and in Northern India, the natural home of the rhesus monkey.

Control of ovulation in cattle with melengestrol acetate. I. Effect of dosage and route of administration.

Abstract: Summary. Dairy heifers with normal oestrous cycles were treated with progestagen for 15 to 18 days beginning at the 15th day of the cycle. Daily oral doses of 0\m=.\25to 8 mg of melengestrol acetate (6\g=a\-methyl-6\x=req-\ dehydro-16-methylene-17-acetoxyprogesterone: mga) inhibited oestrus and ovulation in all heifers except one receiving 0\m=.\5mg. Daily intravenous injections of 0\m=.\4 mg inhibited ovulation in eight out of eight heifers. Lower doses by either route suppressed oestrus but did not uniformly inhibit ovulation. Orally, mga was about 300 to 900 times as potent as map (medroxyprogesterone acetate; Provera*) but only about ten to fifteen times as potent when both were compared by intravenous injection. Groups of eight to ten heifers were fed doses of 0\m=.\2to 2\m=.\0mg daily beginning without regard to the stage of the oestrous cycle. Of seventy\x=req-\ two heifers, sixty-nine did not ovulate during treatment. The average interval from last feeding to oestrus or ovulation ranged from 2\m=.\7 days at 0\m=.\2mg to 6\m=.\3days at 2\m=.\0mg. The conception rates for various groups varied from 25 to 88 % at first service. Of the total, 42 % conceived with one service and 82 % with two services.

Malformations induced by sodium arsenate.

Abstract: The relationship of arsenic administered to pregnant animals and the effect of this metal upon the embryonic system has not been completely investigated. Most studies on this subject have related to the use of organic arsenicals as anti-syphilitic therapy during pregnancy. No evidence exists in mammals for any teratogenic effect of arsenic upon developing embryos although in the chick a direct teratogenic effect has been reported (Ancel, 1947). In mice, the intravenous injection of organic arsenicals results in the apparent storing of this metal in the placenta and a negligible transmission to the foetal tissues (Lebedewa, 1934). Likewise, during the last third of pregnancy in the rabbit, the arsenic is also stored in the foetal portion of the placenta but, as term approaches, increasing amounts of arsenic are found within the foetal tissues (Snyder & Speert, 1938). Eastman (1931) has reported on the use of organic arsenicals in human pregnancies and presented data which suggest that arsenic is rapidly and effectively stored within the foetal portion of the placenta and slowly released into the foetal circulation. This may account for the markedly effective treatment of congenital syphilis with these compounds. None of these mammalian studies have reported on the possible embryocidal

Observations on the acrosomal cap of fixed and unfixed bovine spermatozoa.

Abstract: a comprehensive review of the subject has been published (Hancock, 1966). The structure of the acrosomal cap has been difficult to describe due to alterations which the cap undergoes during cell ageing, or after cell death (Hancock, 1953), and the labile nature of the acrosomal cap to chemical or physical processes involved in tissue preparation for microscopy (Bishop & Austin, 1957). The relationship of acrosome morphology and its alteration to the potentially fertile, motile, immotile or dead cell, as well as the sequence of alteration, must be more clearly understood before the role of this structure in fertilization can be fully evaluated. This report summarizes our observations on freshly collected bovine spermatozoa examined by light and electron microscopy following fixation and by differential interference contrast without fixation. The use of differential interference-contrast microscopy provides a new means by which observations of the acrosome can be made on unfixed cells without the complication of fixation or processing artifacts. Semen was collected from Holstein bulls by means of an artificial vagina. Ejaculates used had, at least, a volume of 3 ml, an initial motility of 60% and a sperm concentration of 700 \\m=x\\106/ml. For electron microscopy, single ejaculates from three different bulls were pooled, and semen was prepared from both raw and diluted aliquots. Dilution was in either previously heated skimmed milk or 2\\m=.\\9%solution of sodium citrate dihydrate. Diluted semen contained 20 \\m=x\\106 motile sperm/ml. Spermatozoa were centrifuged from the diluted or raw semen at 4\\s=deg\\C for 30 min at 750 g. The loose pellet of spermatozoa was transferred to semi-solid 2\\m=.\\5%agar at 29\\s=deg\\C. The agar was permitted to solidify at room temperature following transfer. This provided a means for handling the spermatozoa through dehydration (Blom & Birch-Anderson, 1960). Fixation was in 1% osmium tetroxide solution buffered at pH 7\\m=.\\2to 7\\m=.\\4with veronal-acetate (Palade, 1952) containing sucrose (Caulfield, 1957). Pellets were dehydrated in ethanol and embedded in EPON-812. The agar was removed following dehydration. Thin sections were stained with uranyl acetate and lead citrate.

The distribution of spermatozoa and leucocytes in the female genital tract in goats and cattle.

Abstract: Quantitative studies were made of the distribution of spermatozoa and leucocytes in the female genital tract of mated goats and cows near the time of ovulation and of the leucocytes in the genital tract of unmated goat does at a similar time. In both species, the cervix appeared to act as a reservoir for spermatozoa. Spermatozoa were not uniformly distributed through the lumen of the cervix but tended to be aggregated in the vicinity of the cervical mucosa. The presence of spermatozoa in the genital tract resulted in an increased number of leucocytes in the lumen of the uterus and cervix. In the cervix, the majority of the leucocytes occurred in the central mass of the mucus, this being consistent with the main invasion of the cervical

Differential localization of a male and a female hypothalamic mating centre

Abstract: Implantation of testosterone propionate (tp) in the pre-optic-anterior hypothalamic region produced predominantly male, i.e. homosexual behaviour in female spayed rats. On the other hand, tp implants in the central hypothalamus induced mainly female behaviour, as did subcutaneous tp injections in these animals (D\\l=o\"\\rner,D\\l=o\"\\cke& Moustafa, 1968). Therefore, it was assumed that two different hypothalamic mating centres are responsible for the male and female mating activity. In the following study this hypothesis was reinvestigated by means of intra-hypothalamic implantations of oestradiol benzoate (ob) in rats. Precise quantities of crystalline ob were implanted stereotaxically into the anterior or central hypothalamus of post-puberally spayed female rats of the Sprague-Dawley strain. The stereotaxic implantations were performed according to a method described recently (D\\l=o\"\\cke,D\\l=o\"\\rner& Voigt, 1968). ob was dissolved in alcohol, the solution was aspirated into calibrated glass capillary tubes, and the hormone was implanted after evaporation of the alcohol and recrystallization. The implants were introduced bilaterally anterior or posterior to the bregma according to the stereotaxic atlas of Szent\\l=a'\\gothai,Flerk\\l=o'\\,Mess & Hal\\l=a'\\sz(1968) (A 0\\m=.\\5for implantations in the anterior and P 2\\m=.\\5in the central (middle) hypothalamus). After autopsy each hypothalamus was frozen, serially sectioned at 15 \\g=m\\and stained with haematoxylin and eosin to verify the exact localization of the implants. Tests for sexual behaviour were performed on Days 3, 5 and 7 following the implantation. In the mating tests each rat was exposed for 5 min to (1) a vigorous male, and (2) an oestrous female (Dörner, 1967). Animals with intra¬ hypothalamic cholesterol implants or subcutaneous ob implants served as controls in order to compare the behavioural patterns. The rats of all groups

Mechanisms of zinc, cysteine and selenium protection against cadmium induced vascular injury to mouse testis.

Abstract: It is known that the selective injurious effect of cadmium on the testis can be prevented by zinc cysteine or selenium. Studies conducted in CD-1 mice were initiated to determine whether any of these treatments offered protection by preventing cadmium from reaching the testis in doses sufficient to cause injury. The question of how protection might be offered by this diversity of chemicals formed the basis for the investigations. Using cadmium chloride labelled with cadmium-109 it was shown that none of the protective agents decreased the amount of cadmium reaching the testis. With cysteine the amount of cadmium reaching the testis was actually enhanced. In the presence of selenium there was a 150-250% increase (p<.005) in cadmium uptake by the testis throughout the course of the experiment. And yet of all the protectors known selenium is the most potent completely preventing cadmium damage in a dosage ratio of 2:1. Comparable studies in which selenium rather than cadmium was labelled (selenium-75) demonstrated that in the presence of cadmium selenium levels were augmented. Results from the experiments indicated that the cadmium reaching the testis is somehow inactivated. It is suggested that the protective agents exert their action at the vascular level.

Protein and immunoglobulin content of rete testis fluid of rams.

Abstract: There is little information on the accessibility of the seminiferous tubule to serum proteins and especially to the glycoprotein hormones or to immunoglobulins. The secretions of ram seminiferous tubules may be collected from the rete testis by inserting a cannula via the vasa efferentia (Voglmayr, Scott, Setchell & Waites, 1967), and this paper reports the results of an analysis of these secretions for protein and immunoglobulin.

The post-natal development of the reproductive tract of the Suffolk ram, and changes in the gonadotrophin content of the pituitary.

Abstract: The growth of the pituitary and of the reproductive tract of Suffolk rams from birth to 168 days of age has been studied. Pituitary icsh and fsh concentrations were determined by bio-assay. The pattern of testicular androgen production has been examined using chemical and histological techniques and the relationship to spermatogenesis studied. Pituitary gonadotrophin content increased sharply from 42 days of age but was only weakly correlated with other parameters measured. The androstenedione : testosterone ratio was at its narrowest at birth; however, testosterone was the predominant androgen from birth onwards. Androgen concentration fluctuated but the total content increased with increase in testicular weight. Fructose was present in the seminal vesicles from birth and citric acid from 14 days; citric acid concentration was about one-tenth that of fructose. There was a significant correlation between testicular androgen content and the fructose and citric acid concentration and content of the seminal vesicles. Seminiferous tubule diameter was significantly correlated with most of the parameters measured. Testicular weight increased sharply from 42 days of age. Androgen production was present at birth and preceded spermatogenesis which began when testis weight exceeded 10 g, which was after 56 days of age. Spermatozoa were present in the seminiferous tubules at 112 days of age.

Sperm penetration of pig eggs in relation to the timing of ovulation and insemination

Abstract: The influence of four post-ovulatory ages of egg on the proportion of eggs penetrated by spermatozoa was studied in the pig. The time of ovulation was controlled by an injection ofhuman chorionic gonadotrophin (hcg) given during pro-oestrus. Gilts in oestrus were inseminated 0, 4, 8 or 12 hr after the estimated time of ovulation, and eggs recovered from the oviducts in vivo either 2 or 3 hr later. Eggs were examined from thirteen gilts in each of the four insemination groups. A total of 515 eggs was recovered, giving an overall recovery rate of 86%. Spermatozoa were found attached to or in the zona pellucida of twenty-eight of 117 eggs (24%) recovered 2 hr after insemination and in the perivitelline space of four of these eggs, but none was fertilized. Of 398 eggs recovered from forty animals 3 hr after insemination, 208 eggs (52%) from thirty-one animals had spermatozoa attached to or in the zona pellucida. Twenty-four of these eggs had spermatozoa in the perivitelline space, and 143 (36%) were fertilized. These findings demonstrate that boar spermatozoa can reach and penetrate the zona pellucida of pig eggs within 2 hr of insemination, and can enter the ooplasm and cause resumption of meiosis within 3 hr of insemination. There was no indication that post-ovulatory age as such influenced the number of spermatozoa in the zona pellucida or the proportion of eggs fertilized.

Morphology, motility and fertility of spermatozoa recovered from different areas of ligated rabbit epididymides.

Abstract: was collected six times a week from all males before ligation and for as long as 12 weeks thereafter. Spermatozoa transported normally from the caput to the cauda epididymidis in non-ligated controls were characterized by rapid migration of the protoplasmic droplets, a decrease in swollen acrosomes and other abnormalities, an increase in the percentage of motile cells and a striking increase in fertility. Ligation of the ductus deferens only had little effect upon any of these changes. Also, considerable motility and fertility was maintained for 12 weeks following single ligation in contrast to a reduction after 4 weeks in the group with the isolated cauda epididymidis. This suggests that considerable mixing of spermatozoa normally can occur in the cauda. The proportion of abnormal forms, particularly decapitated spermatozoa, increased considerably in the isolated cauda by 8 weeks. In the isolated caput abnormal spermatozoa increased rapidly and motility decreased. The protoplasmic droplet movement was delayed,

Distribution of adenosinetriphosphatase activity in ram and bull spermatozoa

Abstract: The active transport of sodium and potassium has been demonstrated in dog spermatozoa (Quinn & White, 1967) and the existence of a cation pump, involving a sodium\p=m-\potassiumactivated ATPase has been postulated to account for the gradients of alkali metal ions between the cell and seminal plasma (Quinn, White & Wirrick, 1965). Recently, Uesugi & Yamazoe (1966) have reported the occurrence of a sodium\p=m-\potassiumactivated ATPase in boar epididymal spermatozoa, and the present experiments were undertaken to determine the activity and distribution ofATPases in ram and bull spermatozoa. Semen was diluted with 2\m=.\5vol of 250 mm-sucrose, centrifuged, and the spermatozoa washed twice with 5-ml aliquots of sucrose. Washed spermatozoa, resuspended in sucrose buffered to pH 7\m=.\4(37\s=deg\C) with 50 mm-tris (tris [hydroxylmethyl] amino methane) and 40 mm-HCl were incubated with 3 mm ATP which was rendered free of cations by eluting the disodium salt (Sigma Chemical Co.) through a column of Zeo Carb 226 (H\m=+-\) and restoring the eluate to pH 6\m=.\8with tris. The mixture was incubated at 37\s=deg\C with combinations of 3 mm-magnesium, 150 mm-sodium and 30 mm-potassium chlorides. After 30 min cold trichloroacetic acid was added to give a final concentration of 10% (w/v), the precipitate was centrifuged down at 0\s=deg\C and the phosphorus liberated (difference between 0 and 30 min incubation) measured in the supernatant (Fiske & Subba Row, 1925). Checks showed that this was linear for at least up to 60 min. Both ram and bull spermatozoa exhibited high ATP-splitting activity (Experiment 1, Table 1) in contrast to the last wash fluid from the spermatozoa which had no activity. The activity of the magnesium-dependent ATPase was about 30% higher in whole bull spermatozoa than in ram spermatozoa, and the ATPase activity in the presence of both sodium and potassium was also correspondingly higher in the bull. There was only a slight stimulation of magnesium-dependent ATPase in the presence of either sodium or potassium. When both sodium and potassium were included, ATPase activity increased by 50% over the basal rate, which suggests that a considerable proportion of the ATP is expended in cation transport. The inhibition of cation activation by ouabain parallels a similar effect on the active transport of sodium and potas¬ sium by dog spermatozoa (Quinn & White, 1967). Although the ATPase

A comparison of spermatozoa production and spermatozoa output of yorkshire and lacombe boars

Abstract: boars (av. age 11\m=.\2 months) and 17\m=.\8\m=x\109for ten Lacombe boars (av. age 11\m=.\3 months). The spermatozoa output was 88% of the DSP for the Yorkshire boars and 83% of the DSP for the Lacombe boars when semen samples were collected at 48-hr intervals. Spermatozoa output was significantly correlated ( \m=+-\0\m=.\54) with spermatozoa production. The two breeds did not differ significantly with respect to DSP, but within breeds certain boars produced more spermatozoa than others (P 0\m=.\05). The relative volume of the testes occupied by spermatids with round nuclei did not differ significantly between breeds, among boars within breeds nor between right and left testes. This suggests that for the boar, spermatozoa production is mainly a function of testis size. Results obtained by the procedure for measuring DSP were not significantly influenced by different staining techniques.

Early effect of conceptus on plasma progesterone level in the cow.

Abstract: Progesterone levels in jugular venous blood are being measured by us in cycling (unmated) and inseminated (pregnant or non-pregnant) cows as part of a comparative study of cows with normal and difficult breeding histories. Hawk, Wiltbank, Kidder & Casida (1955) reported a high incidence of embryonic death in cows during the period 16 to 25 days after insemination. The 3rd week of gestation may indeed be a critical phase in the regulation of luteal function, since towards the end of this week regression of the corpus luteum normally occurs in the absence of a conceptus. This note records that in a herd of normal Friesian cattle with a cycle length of 21\m=.\2days \m=+-\1\m=.\5s.d. the presence of a conceptus in the uterus first exerted a significant effect on the peripheral plasma progesterone level on the 19th day after insemination. Samples of blood were collected between 07.30 and 08.00 hours from the jugular veins of cows free from venereal infection or demonstrable lesions of the reproductive tract, at known stages of the oestrous cycle and pregnancy. The blood (about 150 ml) was drawn into vessels containing sodium citrate and cooled rapidly to 4\s=deg\C. The plasma was separated by centrifugation at 4\s=deg\C and stored at \p=m-\18\s=deg\C until analysis, performed usually within 2 weeks. Plasma samples (80 ml) were extracted as described by Lindner, Lunenfeld & Shelesnyak (1967), and the concentration of progesterone in these extracts was determined by the method of Lindner & Zmigrod (1967), which is based on sequential paperand gas-chromatography with a hydrogen-flame detector, and use of a radio-active internal recovery standard. Jugular venous blood collected from a cow 7 days after ovariectomy con¬ tained a detectable, ifvery low, concentration of progesterone (0-17 μg|100 ml) ; 3 weeks after the operation the progesterone level was undetectable (<0-15 μg| 100 ml). The circulating progesterone present 1 week after ovariectomy was probably of adrenal origin (Balfour, Comline & Short, 1957), and surgical stress may have temporarily enhanced such adrenal progesterone secretion. Release ofprogesterone from body fat depots may also have been a contributing factor (cf. McCracken, 1963). The reliability of the assay procedure was tested by replicate determinations of the recovery of progesterone added to plasma from the ovariectomized cow. The results (Table 1) indicated that the procedure was satisfactory.

Endocrine studies at high altitude

Abstract: Nine men were exposed to an altitude of 14,000 ft for 4 weeks. Sperm counts showed persistent decrease, indicating damage early in the spermatogenic cycle. A significant increase of abnormal forms, mainly of the `mature' type, was observed, revealing that damage also occurs at a late stage of spermateliosis. Motility declined without changes in live spermatozoa. Motility changes and fructose elevation

The sponge-tipped catheter--a modification of the open end catheter for recording of myometrial activity in vivo.

Abstract: Many techniques, especially the intra-uterine rubber balloon, have been used for the recording ofuterine contractions in the pregnant and non-pregnant woman. The size of the balloon and its tension, however, greatly influence the results, as Reynolds (1949) has pointed out. Furthermore, it is difficult to maintain exactly the same balloon volume throughout several hours' recording. Some years ago Hendricks (1964) introduced the `open end' catheter technique which is rather simple: a thin, fluid-filled polyethylene catheter is introduced into the cavity of the non-pregnant uterus, and its outer end is connected to a recording system. The fluid surface at the inner tip of the catheter acts as a pressure membrane which transmits the pressure in the slit between the anterior and posterior uterine wall to the fluid within the catheter and thence to the recording instrument. In trained hands this technique works very well and it has been successfully used by Hendricks (1964, 1965, 1966), Bengtsson & Theobald (1966), Bengtsson & Moawad (1966, 1967), Moawad & Bengtsson (1967), Cibils (1967) and Coutinho (1967).

Survival of blastocysts in the uteri of ovariectomized mice

Abstract: Summary. Mature mice were ovariectomized on the 4th day post coitum (Day 1 = vaginal plug) and given no further treatment. Unimplanted (delayed) blastocysts were recovered from these females between 5 and 40 days post coitum. They were tested for viability by determining the proportion that developed into normal foetuses following transfer to Day-4 pseudopregnant recipients. It was found that the proportion of transferred blastocysts developing into foetuses was similar after delays of from 0 to 10 days. After delays of more than 10 days, the proportion of blastocysts that were capable of developing into normal foetuses decreased; 30 to 32% developed following transfer on Days 5 to 15, 18% with transfer on Day 20, and 3% with transfer on Day 30. The finding that blastocysts can be delayed in the absence of ovarian hormones and yet remain capable of developing into normal foetuses demonstrates that progesterone is not essential for blastocyst survival in mice.

Gonadal and epididymal sperm reserves in the rabbit: estimation of the daily sperm production.

Abstract: In the rabbit, daily sperm production by the testes was estimated by determining the total number of spermatozoa and late spermatids contained in a testicular suspension, and the length of the spermatogenic cycle was estimated by an autoradiographic technique. In twenty bucks, 9 to 14 months old (mean weight 3\m=.\9kg), which had spent 6\m=.\9\m=+-\1\m=.\8weeks in a constant photoperiod of 14 hr light daily, the