Hexachlorobenzene (HCB) suppresses circulating progesterone concentrations during the luteal phase in the cynomolgus monkey

Hexachlorobenzene (HCB) is a known reproductive toxin. However, the full spectrum of its reproductive toxicity is unknown. Consequently, the effect of HCB on serum oestradiol (E2) and progesterone (P4) concentrations during the follicular (days 1-9), periovulatory (days 10-14) and luteal (days 15 to beginning of next menses) phases was investigated in the spontaneously cycling cynomolgus monkey. Adult female cynomolgus monkeys (n = 16) were randomly assigned to one of four treatment groups and orally doses with gelatin capsules containing HCB (0.0, 0.1, 1.0 and 10.0 mg kg-1 body wt. day-1) mixed with glucose. A 10-week acclimitization phase was followed by 13 weeks of dosing. HCB induced a dose-dependent suppression of serum P4 concentrations during the luteal phase. However, circulating levels of P4 were unaffected during the follicular and periovulatory phases of the menstrual cycle. Serum E2 concentrations, body weight, menstrual cycle length and duration of menses were not affected by HCB treatment. The range of menstrual cycle length and duration range of menses, however, were broader in the highest dose group. We conclude that HCB interfers with mechanisms regulating ovarian steroidogenesis and suppresses P4 levels during the luteal phase in the cynomolgus monkey.

Ovarian toxicity of hexachlorobenzene (HCB) in the superovulated female rat

Hexachlorobenzene (HCB) is a persistent environmental contaminant which has been measured in human serum, fat, semen, and follicular fluid. In animal testing HCB has been shown to be a reproductive toxin. Discrepant results were obtained from prior studies concerning the effect of HCB treatment on ovarian steroidogenesis. The current study was designed to assess the impact of HCB on the ovary and gonadal steroid levels in the superovulated rat. Female Sprague-Dawley rats (n = 24) were dosed with HCB (0.0, 1.0, 10.0, or 100.0 mg/kg BW/day) for 21 days. All rats received 10 IU pregnant mare serum gonadotropin (PMSG) s.c. on day 18 of treatment and 15 IU of human chorionic gonadotropin (hCG) on day 20. A terminal blood sample was collected and circulating levels of estradiol (E2) and progesterone. (P4) were determined. Serum concentrations of P4 were significantly (p less than 0.0034) elevated by HCB treatment at all dose levels. Ovarian weights were significantly increased (p less than 0.05) in the lowest dose group only compared to the control group. Serum concentrations of E2, uterine weight, weight gain, and general animal health were not affected by HCB treatment. We conclude that during HCB treatment the rat ovary remains responsive to gonadotropin stimulation. Moreover, it is suggested that HCB effects on ovarian steroidogenesis are indirect.

A prospective analysis of endometrial cycle changes by ultrasound in the female cynomolgus monkey

Endometrial cycle changes in adule female cynomolgus monkeys with normal ovulatory cycles were examined prospectively by real-time ultrasound. Endometrial thickness, as measured by ultrasound, was correlated with cycle day and serum estradiol (E2) and progesterone (P4) levels. We conclude that ultrasound is a reliable method of diagnosis of endometrial cycle stage.

Membrane depolarization by isotonic or hypertonic KCl: differential effects on mRNA levels of tyrosine hydroxylase and dopamine beta-hydroxylase mRNA in PC12 cells

Membrane depolarization is an important and common manipulation used to study the result of enhanced neuronal activity on adaptive changes, including alterations in gene expression. In this study, the effect of elevated KCl, under isotonic and hypertonic conditions, on the changes in mRNA levels of the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) was compared. Treatment of PC12 pheochromocytoma cells for several hours with 50 mM KCl, under conditions where osmolarity was maintained, induced TH mRNA levels several fold, without changing DBH mRNA levels (Kilbourne and Sabban, 1990). In contrast, 50 mM KCl added to culture media without adjusting the osmolarity did not alter TH mRNA levels for up to 24 h. Longer continuous exposure to this hypertonic depolarization condition reduced TH mRNA levels to about 10% of control levels. DBH mRNA levels also declined when PC12 cells were treated from 12 h to 5 days with hypertonic 50 mM KCl. The effect appeared to be specific, since actin mRNA levels were elevated about 2-fold with these same hypertonic treatments. As a control for osmotic changes, 50 mM NaCl was used and did not alter TH or DBH mRNA levels. Viability of the cells was maintained and total protein synthesis was reduced somewhat after 12 h of exposure to hypertonic 50 mM KCl, and remained relatively constant for as long as 4 days. Thus, there appears to be an interaction between osmolarity and elevated KCl since very different results of the effects of membrane depolarization on the mRNA levels for the catecholamine biosynthetic enzymes were obtained depending on the osmolarity of the cultures. The extent of elevation of TH mRNA with isotonic KCl was also dependent on cell density. At high cell densities, membrane depolarization no longer induced TH mRNA levels. The results of this study indicate the experimental parameters which can be crucial in studies of membrane depolarization.

The agonist (d-leu-6,des-gly-10)-LHRH-ethylamide does not protect the fecundity of rats exposed to high dose unilateral ovarian irradiation

Attempts to protect the ovary from the toxic effects of radiation and chemotherapy are relevant to the management of the young patient with cancer. Previous studies in a variety of animal species with several types of agonists of GnRH have shown promise in affording gonadal protection using indirect indices of reproductive function. The current investigations are based on these observations. Female rats were treated with (d-leu-6,des-gly-10) LHRH-ethylamide (GnRHa) from day 22 to day 37 of life. Sham-irradiation or unilateral irradiation of the left ovary was performed on day 30. The animals were mated following resumption of cycles and sacrificed on day 21 of pregnancy. There was no significant effect of ovarian artery ligation. Radiation reduced ovarian function ipsilateral to the radiation. GnRHa alone did not affect reproductive performance significantly. GnRHa and radiation combined resulted in no reproductive protection but augmented the damage done to the ipsilateral ovarian weight and to numbers of corpora lutea and fetuses. Under these experimental circumstances the agonist provided no protection.

Rat dopamine beta-hydroxylase: molecular cloning and characterization of the cDNA and regulation of the mRNA by reserpine

A number of cDNA clones for rat dopamine beta-hydroxylase (DBH) were isolated from a rat pheochromocytoma tumor cDNA library. The 2445 nucleotide sequence revealed a single open reading frame of 1860 nucleotides and a 3' untranslated region containing two polyadenylation addition signals. The cDNA coded for a 620 amino acid protein of 69,883 daltons. Six potential glycosylation sites and one potential phosphorylation site were identified. Amino acid residues likely to be involved in the active site of DBH and in copper ligand binding were identified. The N-terminal 42 amino acids appeared to constitute a typical but unusually long signal sequence. Hydropathy analysis indicated that this N-terminal region contained the only extensive hydrophobic domain and thus constituted the only obvious potential membrane attachment site. Northern analysis detected two mRNA species of 2.5 and 2.7 kb. The relative abundance of the 2.7 vs. 2.5 kb mRNAs was differentially regulated in PC12 cells and adrenals. DBH mRNA levels were induced in vivo in rat adrenals upon treatment with reserpine.

Effect of compounds which disrupt proton gradients on secretion of neurosecretory proteins from PC12 pheochromocytoma cells

Treatment of PC12 cells with chroquine (10-50 microM) obliterated the low intragranular pH, as detected by Acridine Orange fluorescence, and depleted the cells of dopamine and norepinephrine. However, these concentrations of chloroquine did not prevent the release of the newly synthesized proteins which normally undergo stimulus-coupled secretion with the catecholamines. Higher concentrations of chloroquine (200 microM) and ammonium chloride (10 and 25 mM) inhibited the release of most of these proteins. This inhibition did not result from alterations in protein synthesis, since the profile of proteins synthesized was not substantially altered. Nor did the inhibition result from degradation of the neurosecretory proteins, since prelabeled proteins were capable of undergoing stimulated secretion from chloroquine-treated cells, as from normal cells. The findings indicated that the inhibition was at the step of packaging of the proteins into the neurosecretory granules. While release of the major secretory proteins, including chromogranin B, was inhibited with 200 microM chloroquine, chromogranin A was secreted upon stimulation of these cells. The results of this study indicate that an acidic intragranular pH is not a requirement for the packaging and secretion of neurosecretory proteins. Higher concentrations of chloroquine had a differential effect on the regulated secretion of different neurosecretory proteins.

Endoglycosidase H susceptibility of secreted and intracellular forms of dopamine beta-hydroxylase

In an attempt to characterize the differences between various forms of dopamine beta-hydroxylase (DBH) the endoglycosidase H (endo H) susceptibilities of the intracellular and secreted DBH were compared. Both soluble and membrane-bound forms of newly synthesized DBH in PC12 cells were found to be susceptible to endo H. Soluble DBH, apparent Mr of 73K, was converted to 67K Mr and membrane-bound DBH, apparent Mr of 77K and 73K, shifted to 69K and 67K. Upon stimulation with the potent secretagogue, BaCl2, over 65% of intracellular dopamine and norepinephrine were secreted together with the soluble proteins of the secretory granules. DBH, released upon this stimulated secretion, was relatively resistant to endo H compared to the intracellular forms.

The effect of medroxyprogesterone acetate (Provera) on ovarian radiosensitivity

Medroxyprogesterone acetate (Provera) is a drug that is commonly given to young women with cancer during chemotherapy and radiation to control heavy bleeding associated with anovulation. Because hypothalamic-pituitary-ovarian suppression has been associated with ovarian protection from the effects of chemotherapy and medroxyprogesterone acetate has been identified as a radiosensitizing agent, we explored the effects of medroxyprogesterone acetate on a rat model with known radiation injury characteristics. Sprague-Dawley rats were treated with medroxyprogesterone acetate or vehicle from day 22 to day 37 of life and were either irradiated or sham-irradiated on day 30 of life and then killed on day 44. Radiation with medroxyprogesterone acetate administration produced a greater loss in preantral and healthy control follicles than in control follicles. No suppression of luteinizing hormone or follicle-stimulating hormone had occurred by day 30 but ovarian glutathione content was reduced. These findings indicate that the administration of medroxyprogesterone acetate with radiotherapy may enhance ovarian injury.

Sclerosis of lytic bone metastases after disodium aminohydroxypropylidene bisphosphonate (APD) in patients with breast carcinoma

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Ice skating accidents and injuries

A total of 169 consecutive injuries to ice skaters is reviewed. The majority resulted from falls and occurred in young people with little or no previous skating experience. Speed and crowding on the ice may be contributory. Injuries occur because of a casual attitude to the sport and because of a lack of awareness of the potentially serious injuries that can result. It would be beneficial for beginners to undergo specific instruction and, if possible, at separate times or in separate areas.

Binding of 125I-labelled human chorionic gonadotropin to cell membrane receptors in rabbit ovarian slices

The binding of 125I-labelled human chorionic gonadotropin (HCG) was studied using thick slices (300 micron) of rabbit ovarian tissue. Binding was saturable, reversible, stereospecific, and of high affinity. The amount of binding was proportional to the number of slices used and could be destroyed by boiling. Ovarian slices from eight individual rabbits were found to have two binding sites for 125I-labelled HCG with KD values of 272 +/- 64 and 1263 +/- 274 pM and Bmax values of 25.7 +/- 5.3 and 94.1 +/- 18.8 fmol/mg protein, respectively. In a comparative study the KD and Bmax values were 351 +/- 151 pM and 25.3 +/- 11.1 fmol/mg protein with slices from one ovary and 134 +/- 24 pM and 109 +/- 32 fmol/mg protein with membranes from the contralateral ovary. These data suggest that the binding of HCG can be determined in live tissue.

Experience with the Portacath

Fifty Portacaths have been inserted in patients undergoing prolonged outpatient chemotherapy, most for haematological disease. Twenty-one are still working at a median duration of 12 months (range 1-27) and a further 15 were functioning normally at the time of the patients death (median survival 6 months). Four functioning Portacaths have been removed, three suspected of causing septicaemia and one believed erroneously to have occluded. Ten have ceased to function and nine of these have been removed. The causes of these failures are nearly all avoidable and are discussed in detail; many occurred early in our experience. With careful attention to detail and with management by trained and interested staff, the Portacath is a safe and reliable device for intermittent vascular access.

Thrombin as an adjuvant to reanastomosis of the fallopian tubes reduces implantations in the rabbit

To study the efficacy of topically administered thrombin as an adjuvant in tubal microsurgery, 24 rabbits underwent a 1-cm resection and microsurgical anastomosis of both fallopian tubes and were randomized to either thrombin or cautery for hemostasis. Ovarian wedge biopsies were done on the left ovary. The animals were mated 4 to 5 weeks postoperatively with a buck of proven fertility. They were killed at 2 to 3 weeks' gestation to note the number of fetuses per patent tube and presence or absence of pelvic adhesions. There was no effect of topical thrombin on the crude pregnancy rate but it was associated with a marked reduction in the number of fetuses per patent tube, despite similar rates of pelvic adhesions between groups. Topically administered thrombin appeared to reduce fertility in this experimental model by an undefined mechanism.

An evaluation of the serum FSH as a biomarker for ovarian toxicity in the rat

There is a need for a biomarker to evaluate numbers of oocytes in an ovary exposed to various exogenous toxicants. Experiments that had been previously reported were reviewed to assess the serum FSH as such a biomarker. Rats that had been exposed to direct ovarian radiation and direct ovarian radiation with cyclophosphamide were reviewed to ascertain the relationship of follicle numbers to the serum FSH. Under the conditions of reduced serum estrogen, linear regression analysis indicated that the serum FSH correlated best with the calculated volume of antral follicles. Receiver operating characteristic curves were calculated to determine that an elevation of the serum FSH two standard deviations above the mean had the greatest diagnostic power in predicting a significant loss in both the number of healthy follicles and the calculated volume of healthy antral follicles. The serum FSH as a biomarker appears to have utility as a measure of the ovarian content of healthy antral follicles rather than as a measure of the total number of oocytes alone.

Effects of ionizing radiation and pretreatment with [D-Leu6,des-Gly10] luteinizing hormone-releasing hormone ethylamide on developing rat ovarian follicles

To assess the effects of a gonadotropin-releasing hormone agonist, [D-Leu6,des-Gly10] luteinizing hormone-releasing hormone ethylamide, in ameliorating the damage caused by ionizing radiation, gonadotropin-releasing hormone agonist was administered to rats from day 22 to 37 of age in doses of 0.1, 0.4, and 1.0 microgram/day or vehicle and the rats were sacrificed on day 44 of age. There were no effects on estradiol, progesterone, luteinizing, or follicle-stimulating hormone, nor an effect on ovarian follicle numbers or development. In separate experiments, rats treated with gonadotropin-releasing hormone agonist in doses of 0.04, 0.1, 0.4, or 1.0 microgram/day were either irradiated or sham irradiated on day 30 and all groups sacrificed on day 44 of age. Irradiation produced a reduction in ovarian weight and an increase in ovarian follicular atresia. Pretreatment with the agonist prevented the reduction in ovarian weight and numbers of primordial and preantral follicles but not healthy or atretic antral follicles. Such putative radioprotection should be tested on actual reproductive performance.

VAD chemotherapy--toxicity and efficacy--in patients with multiple myeloma and other lymphoid malignancies

Thirty-three patients with multiple myeloma (11 untreated, 15 refractory and seven relapsed patients) have received vincristine and adriamycin infusion therapy with oral dexamethasone (VAD). The median number of course received was five. In addition 16 patients with lymphoid malignancy have received a median of four courses of VAD. Three patients who relapsed after VAD have received further VAD therapy making 52 patient treatments assessable for toxicity. Ten per cent had nausea, 4 per cent vomiting, 4 per cent total alopecia, 25 per cent constipation, 33 per cent paraesthesiae, 8 per cent proximal myopathy, 33 per cent dyspepsia, 23 per cent proven bacteraemia, and 19 per cent chest infections. Infections were not usually associated with neutropenia. Shingles was seen in four patients with myeloma, but none of the patients with lymphoid malignancy. The response rate in myeloma was 9/11, for previously untreated patients, 3/7 for relapsed, and 8/15 for refractory patients. Responses have been seen in other lymphoid malignancies-1/2 patients with relapsed acute lymphoblastic leukaemia had a complete remission. Two out of seven patients with chronic lymphocytic leukaemia achieved a partial remission, and a further three had a clinical improvement. Three out of six patients with non-Hodgkin lymphoma and one patient with macroglobulinaemia achieved a partial remission.

Ovarian toxicity of cyclophosphamide alone and in combination with ovarian irradiation in the rat

The effects of radiation and chemotherapy on gonadal function are relevant to the morbidity induced by such treatments. Cyclophosphamide given i.p. to rats on Day 30 of age delayed vaginal opening, prevented vaginal cyclicity, and caused a reduction in serum estradiol and progesterone. Antral follicular atresia increased in a dose-dependent fashion in response to cyclophosphamide (0 mg/kg, 53.5%; 1 mg/kg, 67.3%; 50 mg/kg, 65.7%; 100 mg/kg, 73.9%; 150 mg/kg, 92.2%). Despite such alterations in ovarian function, serum gonadotrophins did not rise. The concurrent administration of 0, 20, 30, 40, 50, and 60 Gy of radiation to the exteriorized ovaries in rats receiving 50 mg/kg cyclophosphamide induced widespread loss of primordial, preantral, and healthy antral follicles associated with reduction in serum progesterone and estradiol. Such irradiation induced dose-related increases in serum follicle-stimulating hormone and luteinizing hormone. Parenteral cyclophosphamide and local irradiation appear to induce ovarian toxicity by different mechanisms.

An analysis of the effects of increasing doses of ionizing radiation to the exteriorized rat ovary on follicular development, atresia, and serum gonadotropin levels

There is increasing interest in the effects of environmental and therapeutic agents on the reproductive system, in particular, the ovary. To study the effects of controlled doses of ionizing radiation to the ovary, Sprague-Dawley rats had their ovaries exteriorized and subjected to increasing doses of radiation. There was a significant increase in ovarian follicular atresia, a significant increase in serum follicle-stimulating hormone levels, but no change in serum luteinizing hormone levels. This experimental protocol may facilitate the testing putative radioprotectants.

Role of sterol carrier protein in cholesterol metabolism

This report summarizes our recent studies on the protein known as sterol carrier protein (SCP) or fatty acid binding protein (FABP). SCP is a highly abundant, ubiquitous protein with multifunctional roles in the regulation of lipid metabolism and transport. SCP in vitro activates membrane-bound enzymes catalyzing cholesterol synthesis and metabolism, as well as those catalyzing long chain fatty acid metabolism. SCP also binds cholesterol and fatty acids with high affinity and rapidly penetrates cholesterol containing model membranes. Studies in vivo showed SCP undergoes a remarkable diurnal cycle in level and synthesis, induced by hormones and regulated in liver by translational events. SCP rapidly responds in vivo to physiological events and manipulations affecting lipid metabolism by changes in level. Thus SCP appears to be an important regulator of lipid metabolism. Preliminary evidence is presented that SCP is secreted by liver and intestine into blood and then taken up by tissues requiring SCP but incapable of adequate SCP synthesis.

Location of the retinoblastoma susceptibility gene(s) and the human esterase D locus

Retinoblastoma occurs with increased frequency in children born with a deletion of the long arm of chromosome 13. Recent reviews have noted that the region 13q14 is consistently deleted in documented cases. Prometaphase and late prophase banding allowed Yunis and Ramsay to determine that a deletion in one patient included the sub-bands q14 . 12, q14 . 13, and q14 . 2, and a portion of q14 . 11 and q14 . 3. We report the results of similar cytogenetic techniques applied in the case of a 26 month old Caucasian female with unilateral retinoblastoma, moderate developmental delay, and subtle dysmorphology. Prometaphase banding of cultured skin fibroblasts revealed the karyotype: mos46,XX/46,XX,del(13)(q13 . 1q14 . 11). Only the sub-band q14 . 11 is deleted in both our patient and that of Yunis and Ramsay. The results are consistent with the localisation of the retinoblastoma susceptibility gene(s) in the sub-band 13q14 . 11. Electrophoretic analysis and activity assays of red blood cell esterase D are consistent with hemizygous expression of that marker in our proband. Comparison with published esterase D analyses in families with retinoblastoma permits the assignment of the esterase D locus to that same sub-band, 13q14 . 11.

Boards must adopt tough stance to meet demands of prospective pricing

Trustees will be confronting a number of new issues arising from the change to a prospective pricing system for Medicare. The author predicts what some of the effects of the new payment system will be, and the behavior changes that must be forthcoming, such as greater cooperation among boards, CEOs, and medical staffs, if hospitals are to succeed under the system.

Oocyte specific regulation of PGK-1 isozyme activity in female germ cells of the mouse

The expression of electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1) was examined during the ontogeny of the female germ-line followingX-chromosome reactivation. Non-growing oocytes from foetal and neonatal ovaries of heterozygous females show a higher PGK-1A isozyme activity, a reflection of prior non-randomX-inactivation favouring activity of theX-chromosome carrying thePgk-1aallele andXceclocus. On oocyte growth, the total PGK-1 enzyme activity increases 40–50 fold and the pattern of PGK-1 isozyme expression changes giving an electrophoretic pattern now skewed in favour of the PGK-1B isozymic form. Activity of the PGK-1B isozyme exceeds that of PGK-1A in all growing oocytes with a total activity greater than 0·075 nmol h−1oocyte−1. Mice homozygous for eitherPgk-1allele show similar PGK-1 specific activities in somatic tissues where oneX-chromosome is active, but oocytes ofPgk-lbhomozygotes show a higher specific activity compared to those ofPgk-1ahomozygotes. Thus increased activity of the PGK-1B isozyme relative to the PGK-1A isozyme is specific to growing oocytes.

X-chromosome inactivation mosaicism in the three germ layers and the germ line of the mouse embryo

Electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1, E.C.2, 7, 2, 3) have been used to examine X-chromosome mosaicism in tissues from 12½-day post coitum heterozygous female mouse embryos. Samples of yolk-sac endoderm, neural ectoderm, heart (mesoderm), liver (endoderm) and germ cells were analysed from each embryo. In all tissues except yolk-sac endoderm, both PGK-1 isozymes were expressed. The extent of covariance among tissues with respect to the PGK-1 isozyme contribution is consistent with all tissues being derived from the same pool of cells after X-inactivation. The covariance among tissues gives an estimate of the size of this pool (47 cells) and places the earliest time of X-inactivation in epiblast cells between 4½ and 5½ days post coitum. From the independent variance among tissues within an individual, the average primordial precursor pool size for the three germ layers and the germ line itself was estimated as 193 cells.

X-chromosome inactivation mosaicism in the three germ layers and the germ line of the mouse embryo

Electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1, E.C.2,7,2,3) have been used to examine X-chromosome mosaicism in tissues from 12 1/2-day post coitum heterozygous female mouse embryos. Samples of yolk-sac endoderm, neural ectoderm, heart (mesoderm), liver (endoderm) and germ cells were analysed from each embryo. In all tissues except yolk-sac endoderm, both PGK-1 isozymes were expressed. The extent of covariance among tissues with respect to the PGK-1 isozyme contribution is consistent with all tissues being derived from the same pool of cells after X-inactivation. The covariance among tissues gives an estimate of the size of this pool (47 cells) and places the earliest time of X-inactivation in epiblast cells between 4 1/2 and 5 1/2 days post coitum. From the independent variance among tissues within an individual, the average primordial precursor pool size for the three germ layers and the germ line itself was estimated as 193 cells.

X-chromosome activity in female mouse embryos heterozygous for Pgk-1 and Searle's translocation, T(X; 16) 16H

To investigate whether the preferential expression of genes on the translocatedXchromosome in female mice carrying theX-autosome translocation T(X; 16)16H (Searle's translocation) is due to non-random inactivation or to cell selection, we examined tissues of mouse embryos heterozygous for the X-linked gene coding for phosphoglycerate kinase (Pgk-1). From the cross T16HPgk-lb/+Pgk-lb♀ × +Pgk-la/Y♂, embryos expressing both isozymic forms of PGK-1 in the epiblast, and only the maternally inheritedPgk-lballele in extra-embryonic tissues, were assumed to be chromosomally balanced, heterozygous female embryos carrying the Searle's translocation (like the mother). The normalXchromosome in this cross carries a high-expressionXceclocus. At 6 days post-coitum (p.c.) both isozymes were equally expressed in the epiblast as expected if bothXchromosomes are active, but by 7 days p.c. the PGK-1B contribution was significantly less than 50%, suggesting thatXinactivation has occurred with a bias towards inactivation of the translocatedXchromosome carrying the lower-expressionXceallele. By 8 days p.c. the situation was the reverse, with aPgk-lbcontribution of significantly more than 50%, and by 12½ days p.c. noPgk-laexpression could be detected. We interpret the dramatic change in isozy me expression between 7 and 8 days p.c. as indicating rapid selection against cells that had inactivated the translocated 16Xchromosome. Two 7-day p.c. embryos unexpectedly showed equal expression of bothPgk-1alleles in both embryonic and extra-embryonic tissues; these were presumably chromosomally unbalanced embryos which had inherited from the mother both an active translocated 16Xchromosome carryingPgk-lband an active normalXchromosome carryingPgk-la.

Random X-chromosome inactivation in female primordial germ cells in the mouse

The pattern of expression of the two X chromosomes was investigated in pre-meiotic germ cells from 12 1/2-day-old female embryos heterozygous for the variant electrophoretic forms of the X-linked enzyme phosphoglycerate kinase (PGK-1). If such germ cells carry the preferentially active Searle's translocated X chromosome (Lyon, Searle, Ford & Ohno, 1964), then only the Pgk-1 allele on this chromosome is expressed. This confirms Johnston's evidence (1979, 1981) that Pgk-1 expression reflects a single active X chromosome at this time. Extracts of 12 1/2-day germ cells from heterozygous females carrying two normal X chromosomes show both the A and the B forms of PGK; since only one X chromosome in each cell is active, different alleles must be expressed in different cells, suggesting that X-chromosome inactivation is normally random in the germ line. This result makes it unlikely that germ cells are derived from the yolk-sac endoderm where the paternally derived X chromosome is preferentially inactivated. In their pattern of X-chromosome inactivation, germ cells evidently resemble other tissues derived from the epiblast.

The hospital's perspective on cost containment

Cost containment has long been a concern of hospitals and the American Hospital Association (AHA). In recent years, however, cost containment has assumed a special prominence in hospitals, becoming both a political and social necessity. The hospitals' and AHA's activities in cost containment fall into four major categories: first, the Voluntary Effort to Contain Health Care Costs, of which AHA is a founding partner; second, administrative effectiveness; third, capital effectiveness, and, finally, medical effectiveness. Some programs to promote administrative effectiveness are shared administrative services, energy conservation, careful attention to staffing patterns and management effectiveness review. Capital effectiveness involves technology assessment and other means of deciding how to make the most of the hospital's dollar. Medical effectiveness can be accomplished by such methods as medical audits, utilization reviews and shared clinical services.

Gearing up for primary care

Although hospitals have long been involved in the provision of primary care services, a new opportunity now exists for hospitals to take the lead in better organizing these services.