Positive fluid balance and diuretic therapy are associated with mechanical ventilation and mortality in preterm neonates in the first fourteen postnatal days

BACKGROUND

Fluid overload leads to poor neonatal outcomes. Diuretics may lower the rates of mechanical ventilation (MV) and mortality in neonates with fluid overload.

METHODS

This is a retrospective study of preterm neonates ≤ 36 weeks of gestational age (GA) in the first 14 postnatal days in a level IV NICU in 2014-2020. We evaluated the epidemiology of fluid balance in the first 14 postnatal days and its association with MV and mortality and studied the association of diuretics with fluid balance, MV, and mortality.

RESULTS

In 1383 included neonates, the overall median lowest and peak fluid balances were - 7.8% (IQR: - 11.7, - 4.6) and 8% (3, 16) on days 3 (2, 5) and 13 (5, 14), respectively. Fluid balance distribution varied significantly by GA. Peak fluid balance of ≥ 10% was associated with increased odds of MV on days 7 and 14 with highest odds ratios (OR) of MV in neonates with fluid balance ≥ 15%. Peak fluid balance of ≥ 15% was associated with the greatest odds of mortality. Diuretics were used more frequently in neonates with younger GA, smaller birthweight, positive fluid balance, and those on MV.

CONCLUSIONS

Positive fluid balance negatively impacts pulmonary status. The odds of MV and death increase significantly as peak fluid balance percentage increases in all GA groups. The impact of diuretics on MV and death in preterm neonates needs further evaluation. A higher resolution version of the Graphical abstract is available as Supplementary information.

The impact of hiring a full-time fertility navigator on fertility-related care and fertility preservation at a pediatric institution

Fertility navigators (FNs) are important in communicating infertility risk and fertility preservation (FP) options to patients receiving gonadotoxic therapies. This retrospective study examined electronic medical records of patients with fertility consults at a large pediatric institution (2017-2019), before and after hiring a full-time FN. Of 738 patient encounters, 173 consults were performed pre-navigator and 565 post-navigator. Fertility consults for long-term follow-up cancer survivors increased most substantially: pre-navigator (n = 7) and post-navigator (n = 387). Across diagnoses, females had a larger increase in consults compared to males (χ² [3, N = 738] = 8.17, p < .05). Findings highlight FNs' impact on counseling rates, particularly in survivorship.

Design and cellular studies of a carbon nanotube-based delivery system for a hybrid platinum-acridine anticancer agent

A three-component drug-delivery system has been developed consisting of multi-walled carbon nanotubes (MWCNTs) coated with a non-classical platinum chemotherapeutic agent ([PtCl(NH3)2(L)]Cl (P3A1; L=N-(2-(acridin-9-ylamino)ethyl)-N-methylproprionimidamide) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-5000] (DSPE-mPEG). The optimized P3A1-MWCNTs are colloidally stable in physiological solution and deliver more P3A1 into breast cancer cells than treatment with the free drug. Furthermore, P3A1-MWCNTs are cytotoxic to several cell models of breast cancer and induce S-phase cell cycle arrest and non-apoptotic cell death in breast cancer cells. By contrast, free P3A1 induces apoptosis and allows progression to G2/M phase. Photothermal activation of P3A1-MWCNTs to generate mild hyperthermia potentiates their cytotoxicity. These findings suggest that delivery of P3A1 to cancer cells using MWCNTs as a drug carrier may be beneficial for combination cancer chemotherapy and photothermal therapy.

Childbirth and consequent atopic disease: emerging evidence on epigenetic effects based on the hygiene and EPIIC hypotheses

Background

In most high and middle income countries across the world, at least 1:4 women give birth by cesarean section. Rates of labour induction and augmentation are rising steeply; and in some countries up to 50 % of laboring women and newborns are given antibiotics. Governments and international agencies are increasingly concerned about the clinical, economic and psychosocial effects of these interventions.

Discussion

There is emerging evidence that certain intrapartum and early neonatal interventions might affect the neonatal immune response in the longer term, and perhaps trans-generationally. Two theories lead the debate in this area. Those aligned with the hygiene (or ‘Old Friends’) hypothesis have examined the effect of gut microbiome colonization secondary to mode of birth and intrapartum/neonatal pharmacological interventions on immune response and epigenetic phenomena. Those working with the EPIIC (Epigenetic Impact of Childbirth) hypothesis are concerned with the effects of eustress and dys-stress on the epigenome, secondary to mode of birth and labour interventions.

Summary

This paper examines the current and emerging findings relating to childbirth and atopic/autoimmune disease from the perspective of both theories, and proposes an alliance of research effort. This is likely to accelerate the discovery of important findings arising from both approaches, and to maximize the timely understanding of the longer-term consequences of childbirth practices.

The P2X7-Egr pathway regulates nucleotide-dependent inflammatory gene expression in microglia

Microglial hyperactivity contributes to neuronal damage resulting from CNS injury and disease. Therefore, a better understanding of endogenous microglial receptor systems that can be exploited to modulate their inflammatory functions is important if better, neuroprotective therapeutics are to be designed. Previous studies from our lab and others have demonstrated that the P2X7 purinergic receptor agonist BzATP attenuates microglial inflammatory mediator production stimulated by lipopolysaccharide (LPS), suggesting that purinergic receptors may be one such receptor system that can be used for manipulating microglial activation. However, although P2X7 receptor activation is well recognized to regulate processing and release of cytokines, little is known concerning its role in regulating the transcription of inflammatory genes, nor the molecular mechanisms underlying these transcriptional effects. In the present studies, we identify that the transcription factors early growth response (Egr)-1, -2 and -3 are downstream signaling targets of P2X7 receptors in microglia, and that their activation is sensitive to MEK and p38 mitogen-activated protein kinase (MAPK) inhibitors. Moreover, using RNAi, we demonstrate that Egr factors and P2X7 receptors are necessary for BzATP-mediated attenuation of iNOS, and stimulation of TNF-α and IL-6 gene expression. BzATP also attenuates neuronal death induced by LPS conditioned medium, and P2X7 receptors are required for this effect. These studies are the first to identify Egr factors as regulators of inflammatory gene expression following P2X7 receptor activation, and suggest that P2X7 receptors may utilize the MAPK-Egr pathway to exert differential effects on microglial inflammatory activities which are beneficial to neuron survival.

Location and type of mutation in the LIS1 gene do not predict phenotypic severity

BACKGROUND

Lissencephaly is a neuronal migration disorder leading to absent or reduced gyration and a broadened but poorly organized cortex. The most common form of lissencephaly is isolated, referred as classic or type 1 lissencephaly. Type 1 lissencephaly is mostly associated with a heterozygous deletion of the entire LIS1 gene, whereas intragenic heterozygous LIS1 mutations or hemizygous DCX mutations in males are less common.

METHODS

Eighteen unrelated patients with type 1 lissencephaly were clinically and genetically assessed. In addition, patients with subcortical band heterotopia (n = 1) or lissencephaly with cerebellar hypoplasia (n = 2) were included.

RESULTS

Fourteen new and seven previously described LIS1 mutations were identified. We observed nine truncating mutations (nonsense, n = 2; frameshift, n = 7), six splice site mutations, five missense mutations, and one in-frame deletion. Somatic mosaicism was assumed in three patients with partial subcortical band heterotopia in the occipital-parietal lobes or mild pachygyria. We report three mutations in exon 11, including a frameshift which extends the LIS1 protein, leading to type 1 lissencephaly and illustrating the functional importance of the WD domains at the C terminus. Furthermore, we present two patients with novel LIS1 mutations in exon 10 associated with lissencephaly with cerebellar hypoplasia type a.

CONCLUSION

In contrast to previous reports, our data suggest that neither type nor position of intragenic mutations in the LIS1 gene allows an unambiguous prediction of the phenotypic severity. Furthermore, patients presenting with mild cerebral malformations such as subcortical band heterotopia or cerebellar hypoplasia should be considered for genetic analysis of the LIS1 gene.

The decrease in plasma melatonin at metamorphic climax in Rana catesbeiana (bullfrog) tadpoles is induced by thyroxine

Melatonin decreases in the plasma of Rana catesbeiana (bullfrog) tadpoles at the climax of metamorphosis when the thyroxine (T(4)) level peaks. Since melatonin inhibited thyroid function in vitro, it would be of interest to determine if the decline in plasma melatonin permits greater thyroid hormone secretion, or if the increasing levels of T(4) cause the climactic decrease in plasma melatonin. The reciprocal effects of administering T(4) or melatonin just prior to metamorphic climax were examined in tadpoles kept at 22 degrees C on an 18L:6D cycle. If melatonin functions as a thyroid antagonist at later metamorphic stages, administration of melatonin should decrease plasma T(4), whereas if T(4) causes the decline in plasma melatonin, T(4) treatment of tadpoles prior to climax should induce the climactic melatonin decrease prematurely. Once daily injection of 40 microg melatonin for 5 days at 19.30 h had no effect on metamorphic progress, or on plasma T(4) or melatonin levels, except for a transient rise in melatonin just after the injection. Immersion in 2.2x10(-4) M melatonin for 6 days accelerated metamorphosis and decreased plasma melatonin, but had no effect on plasma T(4). Administration of T(4) by injection of 0.2 microg, or immersion in a 6.3x10(-8) M solution accelerated metamorphosis more than melatonin immersion, raised plasma T(4) to climax levels, and induced a decrease in plasma melatonin. We conclude that rapid clearance of exogenous melatonin from the circulation in these experiments did not allow it to affect plasma T(4), and that there is clear evidence that the rise in T(4) induces the climax decrease in plasma melatonin. The finding that immersion in a high level of melatonin can lower plasma melatonin and accelerate metamorphosis, whereas a single daily injection does not, provides an explanation for some of the contradictory reports in the literature concerning melatonin's effect on tadpole metamorphic progress.

Direct influence of melatonin on the thyroid and comparison with prolactin

Melatonin administered in vivo had previously been shown to inhibit thyroid cell proliferation and subsequent in vitro thyroxine (T(4)) secretion in anuran tadpoles. Melatonin in vitro also directly reduced the sensitivity of the thyroid to thyrotropin (TSH). The present work sought to determine whether melatonin directly affected baseline, unstimulated T(4) secretion, and to compare its effect with that of prolactin (PRL). Thyroids from larval Rana catesbeiana or adult Rana pipiens were incubated in control or melatonin (0.01 to 100 microg/ml) media. Melatonin directly inhibited T(4) secretion by thyroids from both tadpoles and frogs at all concentrations of melatonin used and at both prometamorphic and climax tadpole stages. PRL, used in vitro at 10 microg/ml, did not influence the response of the thyroid to TSH (0.2 microg/ml) in young tadpoles, or the baseline secretion of T(4) by thyroids at any stage of larval life except climax, when T(4) secretion was significantly decreased by the third day of culture. Thus although both melatonin and PRL have been shown to antagonize the action of T(4) in vitro, and to decrease metamorphic rate, melatonin is a much more effective thyroid gland inhibitor than PRL.

Influence of cortisol on the larval bullfrog thyroid axis in vitro and in vivo and on plasma and ocular melatonin

Adrenal (interrenal) steroids have an important role in amphibian development, antagonizing the metamorphic changes induced by the thyroid at first and then synergizing with the thyroid hormones as their level rises during metamorphosis. Because most of the studies of corticoids at metamorphosis have focused on peripheral tissues, we investigated the effect of cortisol (hydrocortisone; HC) in vitro and in vivo on the thyroid of Rana catesbeiana (bullfrog) tadpoles on 12:12 light/dark (LD) cycles. Plasma and ocular melatonin, which is altered by changes in thyroxine (T(4)) levels, were also assayed in some experiments. Thyroids from premetamorphic tadpoles secreted less T(4) into culture media when incubated with 10 micrograms/ml HC and 0.2 micrograms/ml ovine thyrotropin (TSH) than with TSH alone and when cultured in the absence of TSH following 5 days of 10-micrograms HC injections, indicating that HC inhibited the thyroid at young stages. The effect of 10 micrograms/ml HC at older stages was investigated by culturing thyroids and pituitaries separately on the first day in control or HC media and then incubating the thyroids on the second day in homologous pituitary-conditioned media as a bioassay for pituitary TSH. HC had no effect on baseline T(4) secretion by the thyroids of prometamorphic or climax tadpoles on the first day but increased T(4) secretion over the control on the second day. Thyroids cultured with TSH and HC showed no increase in T(4) secretion over the control TSH group on the second day, indicating that, in the previous experiments, HC had enhanced pituitary secretion of TSH, rather than the response of the thyroid to TSH. In vivo, 5 days of injections of 10 micrograms HC increased plasma T(4) at prometamorphosis and decreased it at climax. There was no marked effect of HC on plasma or ocular melatonin levels. The findings showed that the nature of the effect of HC on the thyroid axis changes during metamorphosis from inhibition at early stages to a positive influence at prometamorphosis and finally to a negative effect on the T(4) level in the plasma at climax.

Hormonal profiles correlated with season, cold, and starvation in Rana catesbeiana (bullfrog) tadpoles

Bullfrog (Rana catesbeiana) tadpoles are of value to amphibian researchers because of their large size, and year-round availability due to overwintering in many latitudes. Concern over a possible difference in hormonal parameters in tadpoles obtained at different times of the year prompted us to investigate thyroid gland secretion in vitro, plasma and ocular melatonin, and plasma corticosteroids in late pre- to early prometamorphic larvae on 12L:12D. Winter tadpoles exposed to 22 degrees C for 3 weeks of acclimation (winter group) were compared to summer tadpoles kept at 22 degrees C (summer group), as well as to summer tadpoles exposed to cold (12 degrees C) for the 3 weeks (cold group), or kept at 22 degrees C and starved for the last week of acclimation (starved group). Thyroids from the summer group had a significantly higher response to 0.2 microg/ml ovine thyrotropin (TSH) than the other groups, indicating that cold and starvation inhibited subsequent in vitro thyroid sensitivity to TSH. The thyroids of the starved tadpoles had significantly higher baseline (unstimulated) thyroxine (T4) secretion into the culture media, a finding that might be related to starvation-induced acceleration of metamorphosis. Plasma melatonin was lower, and ocular melatonin significantly higher in both summer and starved groups, while the reverse occurred in the winter and cold groups. Thus, seasonal or induced cold brought on a shift in the relationship of plasma to ocular melatonin but starvation had no effect. There were no significant differences among the treatment groups in plasma hydrocortisone (HC) and aldosterone (ALDO) levels, except that HC was lower than ALDO only in the plasma of winter tadpoles. We conclude that seasonal variation needs to be taken into account in endocrine experiments utilizing tadpoles obtained at different times of the year.

Distribution and reciprocal interactions of 3H-melatonin and 125I-thyroxine in peripheral, neural, and endocrine tissues of bullfrog tadpoles

Tissue distribution of 125I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the tissue content of the other were studied because previous work indicated that melatonin antagonized metamorphosis through peripheral, as well as thyroidal effects. Late pre- to prometamorphic Rana catesbeiana tadpoles on an 18 light:6 dark cycle were used for injection of hormones in vivo or to supply tissues for in vitro hormone administration. Labeled melatonin uptake was highest in intestine, ventral skin and pituitary; lowest in thyroid and brain and intermediate in hindlimb, tail and gills. The tissue content of labeled T4 was distributed in nearly the same way, except that the thyroid level was relatively higher, and pituitary lower, than that of labeled melatonin. The pineal, studied only in the tracer T4 experiments, had the highest content of labeled T4 of all tissues. Simultaneous injection of either 0.007 or 0.2 microgram T4 increased 3H-melatonin uptake into peripheral tissues that undergo major metamorphic changes but not into neural or endocrine organs. In contrast, 0.033, 3.75 or 15 micrograms melatonin had no significant influence on the content of 125I-T4 in any tissue studied in vivo. Results of in vitro labeling of selected tissues were generally in agreement with the in vivo work except that the 125I-T4 content of intestinal segments from late prometamorphic larvae was lower in melatonin-treated than in control groups. The results suggest that peripheral tissues are a major site for T4-melatonin interactions and that T4 may modulate its own action through influencing melatonin levels in target tissues and perhaps in the thyroid. Because melatonin had no effect on tissue T4 content in young tadpoles, retardation of metamorphic events by melatonin does not seem to involve modulation of T4 availability to the tissues.

Effect of melatonin on the response of the thyroid to thyrotropin stimulation in vitro

Thyroidal-melatonin interactions are of particular importance to amphibian development since the thyroid controls the progress of metamorphosis while melatonin may coordinate its rate with prevailing environmental conditions. Melatonin antagonized thyroxine (T4) action at the tissue level and directly inhibited baseline T4 secretion in culture, so the present work sought to determine if it antagonized the response of the thyroid to thyroid stimulating hormone (TSH) as well. A preliminary experiment showed that, in Rana pipiens, the concentration of TSH (0.2 microg/ml) used in the culture of tadpole thyroids stimulated T4 secretion as much as frog pituitaries, but more than late premetamorphic tadpole pituitaries. There was no significant effect of 1 to 15 microg/ml melatonin in TSH-containing thyroid cultures of various Rana species of tadpoles and frogs in experiments with media collected once every 24 or 48 hr, although 15 microg/ml melatonin tended to depress T4 secretion. In a final experiment, a higher melatonin concentration was used as well as more frequent media collections. Thyroids from prometamorphic Rana catesbeiana tadpoles were cultured in L-15 media with periodic stimulation by 0.2 microg/ml TSH, or TSH and 10 or 100 microg/ml melatonin. Media were collected at the end of two 3-hr TSH pulses, and every 8 hr thereafter for the next 3 days. Melatonin was administered until the end of Day 2 while TSH was given only on Day 2 in addition to the original 3-hr pulses. The secretion of T4 was inhibited significantly by 10 microg/ml melatonin at only two of the early media collections. In contrast, 100 micro;g/ml melatonin significantly depressed T4 secretion in response to TSH at all but one interval and completely inhibited the thyroidal response to TSH reintroduced into the media on Day 2. The findings suggest that a high concentration of melatonin is inhibitory to the thyroidal response to TSH, but that lower concentrations do not significantly overcome the TSH stimulus.

A bitter struggle for integration survival

The state of California created the El Camino Hospital District in 1961, one of 77 such districts created as a way to fund rural hospitals. During the 1990s, hospital administrators began to look for ways to streamline operations and cut costs to remain competitive. In 1992, the hospital District Board voted to turn over El Camino's management to a nonprofit company, believing the hospital could form business partnerships with doctors. The District created a private, nonprofit corporation, approved the appointment of volunteers and physicians to the board, and instructed the board to develop on alliance with other physicians. It became evident that several philosophies were at work regarding the healthcare system. In 1995, the District attempted to void the 1992 agreements and take back the hospital. Legal investigations were initiated. Meanwhile, reimbursement rates were decreasing and the hospital's 600 doctors were dissatisfied. Legal struggles continue, public controversy and physician anger are ongoing, and the Santa Clara County District Attorney's office has begun an audit of records. Camino Healthcare, despite all the ongoing difficulties, continues to provide excellent care to patients and the community.

Effect of melatonin on the anuran thyroid gland: follicle cell proliferation, morphometry, and subsequent thyroid hormone secretion in vitro after melatonin treatment in vivo

The thyroid gland controls the progress of metamorphosis, although other hormones influence metamorphic rate, including melatonin, which may coordinate metamorphosis with seasonal and light conditions. Melatonin directly antagonized the action of thyroxine (T4) in promoting regression of tadpole tail tips in vitro, and this study sought to determine if it affects the thyroid axis of tadpoles as well. In an experiment sampling at 8-hr intervals for 24 hr, after melatonin treatment (15 micrograms/day for 12 days) of premetamorphic Rana pipiens tadpoles at approximately 1100 hr on 18L:6D, thyroid follicle cell height and lumen diameter were lowered by melatonin, but follicle cell proliferation was not significantly depressed. In a second experiment conducted under the same conditions, but sampling at 3-hr intervals for 24 hr, melatonin significantly lowered follicle cell labeling index and suppressed its ultradian (7.6 hr) rhythm, while shifting the peak of follicle lumen diameter to the dark instead of the light. Thus, melatonin tended to depress the thyroid of young tadpoles and suppress or shift its rhythms. Melatonin (10 micrograms/day for 5 days) injected into prometamorphic Rana catesbeiana tadpoles at 1930 hr on 18L:6D significantly altered subsequent in vitro thyroid function as determined by radioimmunoassay of media collected at intervals for 54 hr from cultured thyroids of injected control and melatonin groups, and a noninjected control group. Melatonin decreased T4 secretion during the first 30 hr, but not during the last 24 hr of culture, suppressed 3,5,3'-triidothyronine (T3) secretion for 12 hr, and then raised T3 output into the media above the control for the remainder of the culture period, increasing the T3:T4 ratio. Injection alone increased both T3 and T4 secretion for the first 30 hr, but did not change the T3:T4 ratio. The findings show that exogenous melatonin administered in vivo significantly modulated thyroid activity and morphometry directly and/or indirectly and comprise the first demonstration of an effect of melatonin on the amphibian thyroid gland.

Rotation and radical motion thresholds support a two-stage model of differential-motion analysis

Lower motion thresholds for rotational and radial flow have been measured for stimuli consisting of four closely packed circular apertures, each containing patches of drifting grating or plaid. Detection and direction thresholds were measured for gratings and plaids as a function of the relative orientation of the pattern components. There was a similarity between both types of threshold, supporting the existence of specialised rotation and radial-flow detectors. Further, thresholds increased with the relative component orientation for both gratings and plaids. This suggests that component information from a first stage, tuned spatiotemporally and to orientation, is being used directly to compute the optic flow in a two-stage process. A model based on this architecture is described by means of simple template receptive-field arrays with separable temporal and spatial tuning at the first stage.

Circadian rhythms of thyroid secretion, morphometry, and cell division in prometamorphic and climax Rana tadpoles

Rhythmicity of thyroid follicle structure, cell division, and T4 secretion in vitro was studied in anuran tadpoles on a 12L:12D cycle with light onset at 0800 hr. Stage XIII Rana pipiens larvae had a significant circadian rhythm of follicle lumen diameter (acrophase 1052 hr). Follicle cell height was higher at 0900 hr than at other times but the rhythm was not significant. At Stage XX, both follicle cell height (acrophase 2318 hr) and cell division (acrophase 1929 hr) were rhythmic while lumen diameter, though highest at 0900 hr, showed no significant daily changes. Thyroids from Rana catesbeiana larvae at Stages XVII to XVIII had a significant circadian rhythm of T4 secretion (acrophase 2034 hr) in vitro as measured by radioimmunoassay of media collected every 6 hr for 24 hr. The findings indicate that the daily sequence of thyroid structure and function in preclimax Rana tadpoles includes larger follicle lumina early in the light and maximum cell division, T4 secretion, and follicle cell height within a 4-hr interval beginning around the onset of dark.

Anterior pituitary and adrenal cortical hormones accelerate or inhibit tadpole hindlimb growth and development depending on stage of spontaneous development or thyroxine concentration in induced metamorphosis

The effect of prolactin, growth hormone, and various adrenal corticoids on hindlimb growth, development, and differentiation was studied in Rana pipiens larvae. Experiments were performed at different stages of spontaneous development and during metamorphosis induced in premetamorphic tadpoles by various concentrations of exogenous T4. Prolactin at 10 micrograms/day inhibited the limb at spontaneous premetamorphosis, had no effect at prometamorphosis or when administered with 3.8 nM T4, and synergized with T4 at 63 nM T4 and above. Growth hormone (10 or 20 micrograms/day) promoted limb growth and development during premetamorphosis but had no effect on spontaneous or induced metamorphosis thereafter, nor did it stimulate limb epidermal differentiation. The adrenal corticoids inhibited limb growth and epidermal cell proliferation during pre- and prometamorphosis but had no effect on limb morphogenesis or differentiation. The depressive effect of corticoids during spontaneous metamorphosis is at least partly through thyroid inhibition since hydrocortisone significantly reduced follicle cell height, lumen diameter, and cell proliferation in the thyroid. During induced metamorphosis, steroids (0.29 microM), especially corticosterone and aldosterone, antagonized the effect of 0.38 to 1.2 nM T4 on the limb. All steroids except deoxycorticosterone synergized with 3.8 nM T4, and at 31 nM T4, approximating the climax level with permeability factors taken into account, all corticoids synergized with T4 to promote limb growth and development. Aldosterone antagonized T4 at a higher T4 level than the other corticoids. The effect of all steroids except corticosterone was also corticoid dose-dependent. The results show the importance of the T4 concentrations in interactions of T4 with other hormones and suggest a scheme for hormonal control of limb growth and morphogenesis during metamorphosis. During premetamorphosis growth hormone synergizes with low endogenous T4 to promote initial limb growth and development while prolactin opposes this action. During prometamorphosis, as growth hormone and prolactin become ineffective corticosteroids begin to synergize with the rising level of endogenous T4. At climax, prolactin also augments the action of T4 to bring about rapid hindlimb growth.

DNA synthesis is unaffected but subsequent cell division is delayed in tadpole hindlimb epidermis when thyroxine is given in the dark

In Rana pipiens tadpoles, thyroxine (T4) injection in the early light promotes faster hindlimb growth and development than injection early in the dark. T4 also stimulates a significant increase in cell proliferation in the basal epidermal cells of the limb. Using autoradiography, we studied the timing of the T4-induced rise in the labeling and mitotic indices on 12L:12D cycles with 0.2 micrograms T4 injection early in the light or dark and on a 12L:3D:1L:8D cycle with a light pulse early in the dark shortly after a T4 injection. In all instances, the labeling index peaked at the same time after the start of T4, so diurnal differences in the binding or initial actions of T4 leading up to the entrance of epidermal cells into the DNA synthetic (S) phase of the cell cycle are not indicated. However, with T4 injection in the dark the subsequent mitotic index peak was delayed, to a greater extent on 12L:12D than on 12L:3D:1L:8D. Cells induced to proliferate following T4 injection in the dark evidently had longer cell cycles, probably at the expense of the S or G2 phase, than when T4 was given in the light.

Manpower shortage: multiple competency and cross-training

The terms "cross training" and "multi-competency" have been much confused--Ms. Wright clearly defines the terms and gives some observations on the manpower shortage. Since cost containment will be a fact of life for the '90s, she presents thoughtful strategies to increase productivity and to combat the shortage. Her perspective on changes occurring in our profession over the past two decades provides readers with a thoughtful article.

Metamorphic rate as a function of the light/dark cycle in Rana pipiens larvae

1. The rate of development of Rana pipiens tadpoles in spontaneous and thyroxine (T4)-induced metamorphosis was studied on light/dark (LD) cycles in which the photophase was held constant while the scotophase was progressively extended or vice versa. 2. Metamorphic rate fluctuated in both types of experiments as the LD cycle lengthened. However, the pattern of resonance differed with the length of the photophase. For example, with an 8 hr light phase, development rate slowed and then increased as the cycle was extended from 24 to to 36 hr, whereas with a 12 hr photophase the reverse took place. 3. The findings are compatible with the occurrence of a rhythm of light sensitivity in photoperiodic time measurement in this amphibian. 4. From the viewpoint of hormonal mechanisms, it is suggested that photoperiodic effects on metamorphic rate result from different patterns of melatonin secretion under the various LD cycles, since melatonin can modify the action of T4 in metamorphosis.

Effect of a light pulse during the dark on photoperiodic regulation of the rate of thyroxine-induced, spontaneous, and prolactin-inhibited metamorphosis in Rana pipiens tadpoles

Since Rana pipiens tadpoles injected with thyroxine (T4) early in the dark develop more slowly than those injected in the light, we studied the effect of giving a light pulse of 1 hr early in the dark. Tadpoles injected under a 7.5-W red light bulb in a darkened room with 0.2 microgram T4 daily at 2200 hr went through metamorphosis faster on a 12L:3D:1L:8D cycle with a light pulse after injection than on a 12L:12D cycle without a light pulse, and even faster on a 12L:1.5D:1L:9.5D cycle with a light pulse before the injection. Thus a 1-hr light pulse counteracted the metamorphic delay resulting from administration of T4 in the dark, and set in motion the conditions that resulted in a more rapid response to an injection of T4. However, a 1-hr light pulse in the early dark had no effect on growth and development of older or younger untreated tadpoles or those constantly immersed in 30 micrograms/liter T4. Larvae on 21L:3D with T4 injection in the dark and on 12L:3D:1L:8D with T4 injection at 0700 hr just before the start of the main light phase progressed faster than 12L:3D:1L:8D with injection at 2200 hr in the dark before only a 1-hr light pulse. Thus the length of the light phase immediately after T4 injection was significant. There was no difference on 12L:12D and 12L:3D:1L:8D cycles in the effectiveness of daily injections of 10 micrograms prolactin (PRL) in the early dark at 2200 hr in promoting tail growth or antagonizing tail resorption induced by T4 immersion. Under these conditions, PRL utilization did not appear to be inhibited by the light pulse.

Effect of changing the light/dark schedule, the time of onset of the light or dark period, or the daylength, on rhythms of epidermal cell proliferation

Rhythms of labeling and mitotic indices were studied in the hindlimb epidermis of the anuran tadpole Rana pipiens under different light/dark (LD) cycles and daylengths in order to examine the role of the various parameters of the lighting regimen in setting the periods of the rhythms and the timing of the cell proliferation peaks. Altering the time of, or inverting, the 12 h light period on a 24 h day resulted in phase shifting of basically bimodal circadian rhythms with peaks in the light and dark. Thus the cell proliferation rhythms were entrained to the LD cycle. These rhythms also entrained to noncircadian schedules since they lengthened on a 15L:15D cycle and shortened on a 9L:9D cycle, although the bimodal characteristic of a peak in the light and a peak in the dark remained. Studies of 18L:6D and 6L:18D cycles in which either the time of onset of light or dark was changed relative to the 12L:12D control indicated that the onset of dark may regulate the timing of the labeling index peaks while the onset of light may determine the time of occurrence of mitotic index peaks. Control of the timing of labeling and mitotic index peaks by different parameters of the LD cycle suggests a mechanism for cell cycle regulation by the environmental lighting schedule. Analysis of the rhythms on all the cycles studied suggested that labeling index rhythms equal the length of, or twice the length of, the dark period. Mitotic index rhythms equal the daylength or a multiple of the length of the dark period.

Metamorphic rate in Rana pipiens larvae treated with thyroxine or prolactin at different times in the light/dark cycle

Premetamorphic Rana pipiens tadpoles at Stages V to VIII on a 12L/12D cycle with photoperiod from 0800 to 2000 hr were treated with 30 micrograms/liter thyroxine (T4) by immersion for various daily 8-hr spans, or by daily intraperitoneal injection at different times with 0.1 to 10 micrograms T4 or 10 micrograms prolactin (PRL), in order to see if the rate of metamorphosis varied with the time of hormone treatment. T4 was most effective in promoting tail resorption and hindlimb growth and development if tadpoles were immersed at least partly in the light or if the hormone was injected late in the dark or in the early or mid light phase. T4 was least effective in accelerating metamorphosis when immersion was totally in the dark or injection early in the dark. PRL antagonized metamorphosis just as well at any time of the day except that tail fin growth was faster when PRL was administered early in the dark. The findings show circadian variations in target tissue responsiveness to exogenous T4 that depend on the occurrence of light during T4 immersion or following T4 injection. The data suggest rhythmicity in the secretion of endogenous T4 in the tadpole and a diurnal effect on T4 utilization by target cells.

Non-circadian periodicity in the duration of the cell cycle and the G1 phase in the hindlimb epidermis of the anuran tadpole, Rana pipiens

Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-hr intervals over a 36-hr span in order to see if the cell cycle in the tadpole hindlimb epidermis varied with time or showed rhythmicity. There was a pattern of two long cell cycles followed by a shorter one. Total cell cycle length (Tc) and the length of the G1 phase plus one-half of the mitotic time (TG1 + 1/2M) fluctuated the most, although only TG1 + 1/2M varied significantly with the Chi-square test. The proportion of TC spent in each phase was also calculated. Only TG1 + 1/2M/TC had statistically significant fluctuations with time. Rhythmicity was analyzed by a computer program using the method of least squares for cosine curve fitting. Statistically significant ultradian rhythms of 18.4 hr in TC, 18.5 hr in TG1 + 1/2M and 18.6 hr in TG1 + 1/2M/TC and the length of the DNA synthetic phase/total cell cycle length (TS/TC) were found. Circadian rhythmicity was not observed. The acrophases of the ultradian rhythms of TC and TG1 + 1/2M coincided, suggesting that the rhythm of TC was due mainly to variation in TG1 + 1/2M. In the absence of significant variation in TS, the longest phase of the cell cycle, whenever G1 + 1/2M was short, TS/TC increased, so that the 18.6 hr rhythm in TS/TC was also a result of the periodicity in TG1 + 1/2M.

Rhythms of cell proliferation in the hindlimb epidermis of control and thyroxine-treated Rana pipiens tadpoles

Labeling and mitotic index rhythms were studied in premetamorphic tadpoles under an LD 12:12 with the light phase beginning at 0800 hr. In a 72-hr experiment, control labeling and mitotic index curves showed a peak in the light and a peak in the dark with labeling index rhythms of 12.4, 17.7, and 23.6 hr and a 21.4-hr mitotic index rhythm. Thyroxine (T4) treatment resulted in a marked elevation of labeling index by 24 hr and of mitotic index by 48 hr, obscured the control bimodal pattern of peaks, and altered the rhythms. During the first 3 days of T4 treatment, a labeling index rhythm of 22 hr and a mitotic index rhythm of 37.5 hr occurred. However, additional work demonstrated that the dominant control rhythms of labeling and mitotic indices returned in the T4-treated during Days 4 and 5. The same pattern of change in labeling index occurred during Day 3 of T4 treatment when hormone administration began at different times in the diurnal phase of the light-dark cycle. The findings suggest that cell proliferation rhythms can be temporarily disturbed by an exogenous T4 stimulus without apparent reference to the phase of the circadian rhythm.

Pulmonary vascular changes in young and aging rats exposed to 5,486 m altitude

Young (YNG) and middle-aged (MA) male rats were exposed to 5,486 m for durations ranging from 1 to 42 days to determine the effect of age on the progression of polycythemia, right ventricular hypertrophy (RVH), lung vascular muscularization, and pulmonary vascular responsiveness. Other rats were exposed for 42 days at 5,486 m and were then allowed to recover at 1,520 m for periods up to 42 days. The progression and subsequent regression of polycythemia and RVH with altitude exposure were similar for YNG and MA rats. However, YNG rats exhibited vascular muscularization during the altitude exposure, characterized by hypertrophy of smooth muscle cells, whereas MA rats exhibited little or no change in vascular morphology. Lungs from both altitude-exposed YNG and MA rats exhibited blunting of acute hypoxic pulmonary vasoconstriction upon exposure to 5,486 m, with more severe blunting apparent in MA rats. Pressor responses to angiotensin II (AII) were potentiated in lungs from high altitude rats, particularly in the YNG rats, and this increased responsiveness persisted during the recovery period. A positive correlation was found in YNG rats between the degree of vascular muscularization and the pressor response to AII, suggesting that increased muscle mass was partially responsible for the potentiated AII responses. However, MA rats did not exhibit the same correlation for AII, and neither YNG nor MA rats exhibited increased responsiveness to 5-hydroxytryptamine. The results indicate that age influences the morphologic responses to altitude exposure and vascular responsiveness to AII, but does not affect the polycythemic response or the degree of RVH.

Altered vascular responsiveness in isolated perfused lungs from aging rats

Systemic vascular hyporesponsiveness has been well documented in aged rats, but a similar decreased vasoreactivity of the pulmonary vasculature has not been reported. Isolated lungs from young (3-5 months) and middle-aged (12-14 months) rats were perfused with whole blood and challenged alternately with alveolar hypoxia, angiotensin II, and 5-hydroxytryptamine. Hypoxic pulmonary vasoconstriction was less in the aging rats during both 5-min and 10-min hypoxic exposures. Likewise, log-dose response curves for angiotensin II and 5-hydroxytryptamine were right-shifted in the aging rats, indicating decreased responsiveness to the vasoactive agents. Since the vascular responses to all three vasoconstrictors were lower in the older animals, a generalized pulmonary vascular hyporeactivity with advancing age is suggested.

Application of benefit-to-cost analysis to an X-linked recessive cardiac and humeroperoneal neuromuscular disease

Benefit-to-cost analysis (using standard economic methods) and the predictive tools of genetics are important in the assessment of genetic services for high burden, single gene disorders. We have studied 6 generations of a 167-member, stable, North Georgia kindred at risk for X-linked recessive humeroperoneal neuromuscular disease with cardiac conduction defects. This disorder began in affected males in the teen years, with total disability expected by the 3rd decade and death by age 50. Using known fecundity rates and Mendelian probabilities, 26.6 heterozygous females and 9.4 hemizygous affected males were expected in the currently developing generation. We compared the compensatory costs for families with affected males against costs of genetic intervention for this disorder. All costs and benefits were discounted to present values at 6% and 10% and a benefit-to-cost ratio was derived. At a 6% discount rate the benefit-to-cost ratio was 21 to 1 while at a 10% discount rate the benefit-to-cost ratio was 14 to 1. We conclude that although this is an unusual X-linked muscular dystrophy, it constitutes a prototypic public and private expense which is largely preventable. The method of cost accounting within pedigrees has wide applicability. The results reemphasize the economic benefit of comprehensive public health programs in genetics, particularly in areas with stable, high risk-populations.