Pregnancy and diabetes. Team approach.

Each year, 10,000 babies are born to diabetic women. Gestational diabetes occurs in 2% of all pregnant women, resulting in 60,000 to 90,000 cases of gestational diabetes yearly. Prior to 1922 and the discovery of insulin, fetal mortality for the pregnant diabetic was almost 100%. Today, total fetal mortality for the pregnant and gestational diabetic is approaching that of the nondiabetic. This has been achieved by extremely tight control of blood glucose levels throughout pregnancy, with blood glucose levels averaging under 100 mg/dL/day and glycosylated hemoglobin levels in the normal range throughout pregnancy. An increased number of malformations in fetuses of pregnant diabetic women is still a problem. However, animal and human studies indicate that a normal level of glycosylated hemoglobin at conception may significantly reduce these malformations.

Hypoglycemic coma associated with subcutaneous insulin infusion by portable pump.

The incidence of hypoglycemia in insulin-dependent diabetic patients managed by continuous subcutaneous insulin infusion (CSII) has been reported to be very low. We report a case of hypoglycemia coma occurring in a highly compliant and intelligent patient while on CSII by a portable pump. Factors contributing to this episode included high risk off hypoglycemia due to tight control, failure to recognize early hypoglycemic symptoms, and maintenance of hypoglycemia for over 2 h by the open-loop device. Hypoglycemia is a complication of CSII by portable pump. We join others in recommending its use solely by experienced physicians. Constant supervision of patients while on CSII is important to eliminate this potentially lethal complication.

NO-cGMP pathway increases the hyperpolarisation-activated current, I(f), and heart rate during adrenergic stimulation.

OBJECTIVES: The role of the nitric oxide (NO)-cGMP pathway in the autonomic modulation of cardiac pacemaking is controversial and may involve an interplay between the L-type calcium current, I(CaL), and the hyperpolarisation activated current, I(f). We tested the hypothesis that following adrenergic stimulation, the NO-cGMP pathway stimulates phosphodiesterase 2 (PDE2) to reduce cAMP dependent stimulation of I(f) and heart rate (HR). METHODS: In the presence of norepinephrine (NE, 1 microM), the effects of the NO donor sodium nitroprusside (SNP) were evaluated in sinoatrial node (SAN)/atria preparations and isolated SAN cells from adult guinea pigs. RESULTS: Contrary to our hypothesis, SNP (10 and 100 microM, n=5) or the membrane permeable cGMP analogue, 8Br-cGMP (0.5 mM, n=6) transiently increased HR by 5+/-1, 12+/-1 and 12+/-2 beats/min, respectively. The guanylyl cyclase inhibitor 1H-(1,2,4)-oxadiazolo-(4,3-a)-quinoxalin-1-one (ODQ, 10 microM, n=5) abolished the increase in HR to SNP (100 microM) as did the I(f) blockers caesium chloride (2 mM, n=7) and 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino)-pyrimidinium chloride (ZD7288, 1 microM, n=7). Addition of SNP (10 microM) also transiently increased I(f) in SAN cells (n=5). After inhibition of PDE2 with erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA, 10 microM, n=5), the increase in HR to SNP in the presence of NE was significantly augmented and maintained. RT-PCR analysis confirmed the presence of PDE2 in addition to cGMP inhibited PDE3 mRNA in central SAN tissue. CONCLUSIONS: These results suggest that during adrenergic stimulation, activation of the NO-cGMP pathway does not decrease HR, but has a transient stimulatory effect that is I(f) dependent, and is limited in magnitude and duration by stimulation of PDE2.

Localisation and functional significance of ryanodine receptors during beta-adrenoceptor stimulation in the guinea-pig sino-atrial node.

OBJECTIVE: Recent evidence shows that calcium released from the sarcoplasmic reticulum (SR) plays an important role in the regulation of heart rate. The aim of this study was to investigate the subcellular distribution of ryanodine receptors in the guinea-pig sino-atrial (SA) node and to determine their functional role in the regulation of pacemaker frequency in response to beta-adrenoceptor stimulation. METHODS: Monoclonal antibodies raised against the cardiac ryanodine receptor were used with confocal microscopy to investigate ryanodine receptor distribution in single guinea-pig SA node cells. The functional role of ryanodine receptors was investigated in both multicellular SA node/atrial preparations and in single SA node cells. RESULTS: Ryanodine receptor labelling was observed in all SA node cells studied and showed both subsarcolemmal and intracellular staining. In the latter, labelling appeared as transverse bands with a regular periodicity of approximately 2 microm. This interval resembled that of the expected sarcomere spacing but did not, however, depend on the presence of transverse tubules. The bands of ryanodine receptors appeared to be located in the region of the Z lines, based on co-distribution studies with antibodies to alpha-actinin, myomesin and binding sites for phalloidin. Functional studies on single SA node cells showed that application of ryanodine (2 micromol/l) reduced the rate of firing of spontaneous action potentials (measured using the perforated patch clamp technique) and this was associated with changes in action potential characteristics. Ryanodine also significantly decreased the positive chronotropic actions of isoprenaline in both multicellular and single cell preparations. In single cells exposed to 100 nmol/l isoprenaline, ryanodine caused a decrease in the rate of firing and this was associated with a decrease in the amplitude of the measured calcium transients. CONCLUSIONS: These findings are the first to show immunocytochemical evidence for the presence and organisation of ryanodine receptor calcium release channels in mammalian SA node cells. This study also provides evidence of a role for ryanodine sensitive sites in the beta-adrenergic modulation of heart rate in this species.

Nitric oxide does not modulate the hyperpolarization-activated current, I(f), in ventricular myocytes from spontaneously hypertensive rats.

OBJECTIVE: : In sinoatrial (SA) node cells, nitric oxide (NO) exerts a dual effect on the hyperpolarization-activated current, I(f), i.e. in basal conditions NO enhances I(f) whereas in the presence of beta-adrenergic stimulation it decreases it. Recent studies have shown that I(f) is present in ventricular myocytes from hypertrophied or failing hearts where it may promote abnormal automaticity. Since these pathological conditions are associated with increased sympathetic tone and upregulation of myocardial NO production, we set out to investigate whether I(f) is similarly modulated by NO in hypertrophied ventricular myocytes. METHODS: Left ventricular myocytes were isolated from 18-20-month-old spontaneously hypertensive rats (SHRs). Membrane current was measured under whole-cell or amphotericin-perforated patch-clamp conditions, at 35 degrees C. RESULTS: Application of diethylamine-NO (DEA-NO, 1-100 microM) did not alter the amplitude or voltage dependence of activation of I(f) under basal conditions (half-activation voltage, V(h): control -82.9+/-2.6, DEA-NO -84.0+/-2.6 mV). Similarly, I(f) was not affected by the inhibition of endogenous NO production (L-NMMA, 500 microM) or guanylate cyclase (ODQ, 10 microM). Forskolin (10 microM) or isoprenaline (100 nM) elicited a positive shift in V(h) but subsequent application of DEA-NO did not further affect the properties of I(f). CONCLUSIONS: Our results show that, unlike in SA node cells, in SHR ventricular myocytes basal and adrenergically stimulated I(f) is not modulated by exogenous NO or by constitutive NO or cGMP production.

The response of pancreatic and pituitary hormones to pulses and constant infusion of somatostatin.

The inhibitory action of pulses and constant infusion of somatostatin on the secretion of pancreatic and pituitary hormones was studied serially in 7 normal men and 2 untreated acromegalics. In normal men, significant inhibition of basal release of insulin and glucagon was elicited by as little as 1 mug dose of a pulse of somatostatin. Increasing doses of somatostatin (5, 50, 250 and 500 mug) given as a single pulse at weekly intervals produced what appears to be a decreased inhibition of glucagon while no measurable relationship between the dose of somatostatin and the degree of inhibition of insulin was seen. Given during the same day, incremental doses (from 1 to 250 mug) of pulses of somatostain produced a progressive decline in both glucagon and insulin. The elevated basal levels of GH, insulin and glucagon seen in acromegalics, were inhibited by a pulse of somatostatin as little as 2 mug. These inhibitions were sustained during the constant infusion of somatostatin (2.5 mug/min), and a rebound in GH, insulin and glucagon appeared promptly following the infusion.

The effects of ovariectomy and estrogen treatment on the dopamine inhibition of gonadotropin and prolactin release.

The suppressive action of dopamine (DA) on circulating gonadotropin and PRL levels is found to be positively correlated with their basal serum concentrations. Thus, DA inhibition is greater in ovariectomized (agonadal) women than in normal women on day 2 of their menstrual cycles, and the reverse is observed for PRL. Pretreatment of agonadal subjects with estrogen lowers the basal levels of LH and FSH and thereby proportionately decreases the suppressive effects of DA. Estrogen treatment elevates the basal level of PRL in agonadal subjects and also the PRL-inhibiting effect of DA. These findings indicate that castration and estrogen treatment significantly influence the inhibitory effect of DA on gonadotropin and PRL release.

Efficacy of intravaginal and intranasal administration of micronized estradiol-17beta.

Absorption of micronized 17beta-estradiol (E2), after intravaginal administration of 1 mg dose, suspended in saline, is extremely rapid and sustained. A mean peak increment of circulating E2 concentrations of more than 110 times the basal level is achieved at 2 h and remains elevated more than 6 times the basal level even at 24 h. Increments in estrone (E1) are smaller and slower than those of E2 with a mean peak concentration of less than 10% of E2 and remain 3 times the basal level at 24 h. With 0.5 mg dose, the incremental changes in E2 and E1 as well as the degree of gonadotropin suppression are essentially the same. In contrast, intranasal administration of E2 of 1 mg dose induces a rapid but short-lasting increase in both serum E2 and E1 levels. The mean increments of E1 exhibited a higher and sustained elevation with a rise in mean E1/E2 ratio well above unity beginning 1 hr after intranasal application. These findings indicate intravaginal but not intranasal routes of E2 absorption are quantitatively much greater and circumvent the local conversion of E2 to E1 observed after oral administration of E2, and thus represent a practical and highly effective means of delivering E2 into the circulation.

The effects of ovarian wedge resection on circulating gonadotropin and ovarian steroid levels in patients with polycystic ovary syndrome.

Serum gonadotropin, estrogen, and androgen levels were measured daily before and up to 35 days after surgery in 8 patients with polycystic ovary syndrome (PCO) undergoing ovarian wedge resection (WR). To serve as controls, similar assessments were made in 5 women having hysterectomies for non-ovarian disease during the early follicular phases of their cycles. Preoperatively, LH but not FHS, estrone (E1) but not estradiol 17 beta (E2), and both androstenedione (delta) and testosterone (T) levels were higher in the PCO patients than in the normal women. In the PCO patients, surgery had no discernible effect on FSH levels. In the 5 PCO patients who apparently ovulated after WR, LH levels did not fluctuate significantly until the midcycle LH peaks occurred 13-25 days after surgery. In the 3 patients who did not ovulate, there was a transient fall of LH, which reached a nadir on the sixteenth postoperative day and then returned to preoperative levels. In the total PCO group there was a significant fall of E1 (P less than 0.05) and a decrease of E2, which reached nadirs on the third postoperative day. Preovulatory rises of both E1 and E2 were seen only in patients who ovulated following WR. For the androgens, significant decreases (P less than 0.05) of both T and delta were seen during the first 3 days after WR. These were followed by steady increases of both androgens back to preoperative levels. Delta levels remained elevated while T concentrations fell again and were significantly lower (P less than 0.005) at the end of the sampling period than preoperatively. This pattern was seen whether the patients did or did not ovulate. Except for a small transitory fall of androgens, surgery had no discernible effect on the circulating levels of any of the hormones in the control subjects. These results show that in PCO patients, ovarian WR is followed by a profound, temporary reduction of ovarian delta secretion and a persistent reduction of T secretion. Smaller, but significant, decreases of estrogen production were also observed. The mechanism responsible for ovulation following WR appears to be local (intra-ovarian) rather than central since the alterations in ovarian hormone secretion had no discernible effect on circulating gonadotropin levels prior to the onset of midcycle surges.

Class H diabetes and pregnancy.

Class H diabetes is defined as the presence of diabetes of any duration associated with ischemic myocardial disease. Because of a lack of experience with the coexistence of myocardial ischemic disease and diabetes during pregnancy, it is difficult to offer patients an accurate prognosis for mother and infant during such a gestation. Previous reports suggest that outcomes in this situation are almost routinely poor. It is likely, however, that there is a subset of patients within the class H diabetic population in whom pregnancy can be successful. Reported are the pregnancies of three such patients. The authors suggest that careful attention to cardiac status and glycemic control contribute to both maternal and fetal well-being. Prepregnancy screening of class H patients for evidence of cardiac dysfunction may allow for the screening of those class H diabetic women who are most likely to achieve successful pregnancy outcome.

Gestational carcinoma of the female breast.

Few neoplastic diseases can equal the amazing complexity and sheer perversity of carcinoma of the breast. No doubt as many decades of research lie ahead in its study as already have passed. Clinicians have long appreciated the special relationship of the disease to gestation. Diagnosis and treatment of breast cancer during pregnancy represent only a small part of this fascinating relationship. Although indispensable as research tools, animal models pertain to the human disease only in limited, ill-defined ways. The etiology of human breast cancer remains unclear; chemical, viral, hormonal, genetic, and immunologic theories have all been put forward as possibilities. Although gestation clearly alters both the initiation and growth of mammary tumors, its exact role in the various theoretical considerations remains a mystery. The obstetrician-gynecologist holds an important front-line position in the war against breast cancer, as does any provider of primary care to women, and, indeed, as do women themselves. Rather than decrease vigilance during pregnancy, the physician should pursue with extra vigor any breast mass discovered in the gravid patient, when the clinical examination is even less reliable than usual. The finding of a breast mass usually necessitates biopsy. Except for the inclusion of specific pregnancy-related problems, such as galactocele, the diagnostic spectrum of breast masses removed during pregnancy does not differ from that in nonpregnant women. The discovery of a highly suspicious breast mass, or the confirmed biopsy diagnosis of malignancy, in a pregnant patient should indicate the need for referral to a surgical oncologist versed in this unusual problem. The best approach to gestational breast cancer continues to be the team approach, with consultation from specialists in obstetrics, surgical oncology, anesthesiology, nuclear medicine, radiology, radiation oncology, pathology, and medical oncology. The age and general condition of the patient, the extent of the tumor, the stage of gestation, and the informed opinions of the patient and her spouse help to determine the therapeutic strategy. Careful staging not only guides present therapy but also the therapy of future victims through continued investigation. Most surgeons favor operation without delay if cure seems within reach. Mastectomy, with or without cesarean section, can be accomplished without detriment in the hands of a knowledgeable surgeon-anesthesiologist team. By following certain guidelines, the search for metastasis can be conducted safely and appropriately. The clinical situation occasionally may require the initiation of adjuvant radiotherapy or chemotherapy during pregnancy, by experienced consultants. Ongoing studies of tissue hormone receptors and cell kinetics will continue to give insight into the effects of gestational hormones on breast cancer and can aid in the selection of treatment options for the individual patient...

Rh isoimmunization complicating a triplet gestation. A case report.

A case occurred of Rh isoimmunization complicating a triplet gestation. Management of that extremely rare situation required careful attention to the problems inherent in both multiple pregnancy and isoimmunization. Amniocentesis and frequent antepartum fetal monitoring were the cornerstones of therapy.

What determines the initiation of the heartbeat?

The origin of the heartbeat in the sino-atrial (SA) node is usually thought to arise from the sequential activation of a variety of ionic currents in pacemaker cells (Irisawa et al. 1993). Recently, the possibility has been considered that heart rate might be influenced by transient changes in cytosolic Ca2+. Rubenstein & Lipsius (1989) demonstrated that in cat subsidiary pacemaker cells the late phase of diastolic depolarization was slowed in the presence of ryanodine to selectively inhibit Ca2+ release from the sarcoplasmic reticulum (SR). Primary pacemaker cells also have a SR-dependence of cardiac pacemaking since the rate of beating of guinea-pig SA node/atrial preparations was slowed in the presence of either ryanodine or cyclopiazonic acid (an inhibitor of the SR Ca2+-ATPase). The reduction in rate was associated with changes in action potential characteristics recorded intracellularly (Rigg & Terrar, 1996). The role of Ca2+ release from the SR in influencing pacemaker rate appears to be a common mechanism in many types of pacemaking tissue since the rate reducing effects of ryanodine have been observed in other mammalian cells (rabbit SA, e.g. Hata et al. 1996; and atrioventricular node, Hancox et al. 1994) and in amphibian pacemaker cells (Ju & Allen, 1998).

Multiphasic prolactin secretion during parturition in human subjects.

Prolactin (PRL) secretion in the periparturitional period in patients undergoing labor and vaginal delivery follows a remarkable multiphasic pattern not found in patients who underwent elective cesarean section without labor. There is a highly significant decline in PRL levels during active labor which reaches a nadir about two hours prior to delivery. Immediately after delivery, a surge of PRL is noted, reaching peak levels within two hours post partum. Thereafter, PRL levels fall, reaching a second nadir about nine hours post partum, and this low level is maintained for nine to 24 hours after delivery. This multiphasic pattern of PRL secretion is not correlated with changes in serum concentrations of cortisol, progesterone, estradiol, or estrone. PRL levels in all pregnant patients at term were unaffected by the administration of synthetic narcotic analgesic agents, anesthesia, or the stress of operation. It is concluded that PRL secretion in the pregnant patient at term is unresponsive to usual stimuli and that the multiphasic pattern of PRL secretion uniquely found with labor and vaginal delivery may be associated with dopaminergic neuroendocrine processes during human parturition.

125I insulin receptor binding characteristics on umbilical cord blood erythrocytes from normal and diabetic pregnancies.

Umbilical cord blood erythrocyte insulin receptor characteristics of 13 normal and 14 diabetic pregnancies were evaluated to elucidate the effect of maternal diabetes on fetal insulin binding. Specific insulin binding to erythrocytes was similar in the two populations. However, in comparison to infants of nondiabetic women, infants of diabetic mothers exhibited a fourfold decrease in receptor affinity and a fourfold increased number of receptor sites in spite of significant hyperinsulinemia. The in utero infant of a diabetic mother therefore functions with a comparatively low affinity/high capacity insulin binding system that allows it to maintain normal insulin sensitivity in the presence of hyperinsulinemia. This altered, but balanced, mechanism may play an important role in glycemic homeostasis in utero and in the development of neonatal hypoglycemia.

Possible role of calcium release from the sarcoplasmic reticulum in pacemaking in guinea-pig sino-atrial node.

Ryanodine and cyclopiazonic acid were used to alter the ability of the sarcoplasmic reticulum (SR) to store calcium. Interventions of this kind significantly reduced the rate of spontaneous beating of guinea-pig sino-atrial node preparations. In addition, both of these drugs decreased the rate of rise and modified other characteristics of the action potentials recorded from this region. It is proposed that calcium released from the SR plays an important, previously unrecognized, role in pacemaking in the sino-atrial node, possibly through regulation of sarcolemmal ionic currents.

The impairment of progesterone-induced pituitary release of prolactin and gonadotropin in patients with hypothalamic chronic anovulation.

Sequential administrations of progessively increasing amounts of estradiol benzoate (EB) for five days followed by 10 mg. of progesterone (P) elicited a prompt pituitary release of luteinizing hormone, follicle-stimulating hormone, and prolactin in normal women during the early follicular phase but not in women with normogonadotropic hypothalamic chronic anovulation with or without associated hyperprolactinemia. Since hypothalamic dopamine functions as an inhibitor for the secretion of both prolactin and gonadotropin, we postulate that sequential EB-P stimulation for simultaneous release of gonadotropin and prolactin may be mediated by a reduction of hypothalamic dopamine in response to progesterone. The failure of patients with hypothalamic chronic anovulation to respond to this sequential ovarian steroid feedback demonstrated in this study may indicate the presence of dopaminergic dysfunction and that this test may prove to be useful in delineating hypothalamic function in amenorrhea patients.

Pattern of increase in circulating prolactin levels during human gestation.

Serum prolactin concentrations, determined serially at weekly intervals from the fifth week of gestation, increase in an approximately linear pattern. It is suggested that in human gestation the increase in prolactin secretion is related to supramaximal estrogen augmentation at all times and is a functional reflection of hypertrophy and hyperplasia of pituitary lactotrophs.

Constancy of serum angiotensin-converting enzyme activity in normal and complicated pregnancy.

Angiotensin-converting enzyme occupies a central position in the dynamics of the renin-angiotensin system. We prospectively studied serum angiotensin-converting enzyme activity in 112 women at various stages of pregnancy and in the postpartum period because converting enzyme levels have not been well documented in pregnant women with medical disorders which might be expected to influence intravascular volume or blood pressure. Enzyme activity is lower during pregnancy than it is in the same population at 6 weeks postpartum. Levels of serum angiotensin converting enzyme activity remain relatively stable during gestation but drop during the immediate postpartum period. Diabetes, chronic hypertension, and pregnancy induced hypertension fo not markedly change serum angiotensin converting enzyme activity.

Role of cGMP-inhibited phosphodiesterase and sarcoplasmic calcium in mediating the increase in basal heart rate with nitric oxide donors.

Nitric oxide (NO) donors increase heart rate (HR) through a guanylyl cyclase-dependent stimulation of the pacemaker current I(f), without affecting basal I(Ca-L). The activity of I(f)is known to be enhanced by cyclic nucleotides and by an increase in cytosolic Ca(2+). We examined the role of cGMP-dependent signaling pathways and intracellular Ca(2+)stores in mediating the positive chronotropic effect of NO donors. In isolated guinea pig atria, the increase in HR in response to 1-100 micromol/l 3-morpholino-sydnonimine (SIN-1; with superoxide dismutase, n=6) or diethylamine-NO (DEA-NO, n=8) was significantly attenuated by blockers of the cGMP-inhibited phosphodiesterase (PDE3; trequinsin, milrinone or Ro-13-6438, n=22). In addition, the rate response to DEA-NO or sodium nitroprusside (SNP) was significantly reduced following inhibition of PKA (KT5720 or H-89, n=15) but not PKG (KT5728 or Rp-8-pCPT-cGMPs, n=16). Suppression of sarcoplasmic (SR) Ca(2+)release by pretreatment of isolated atria with ryanodine or cyclopiazonic acid (2 micromol/l and 60 micromol/l, n=16) significantly reduced the chronotropic response to 1-100 micromol/l SIN-1 or DEA-NO. Moreover, in isolated guinea pig sinoatrial node cells 5 micromol/l SNP significantly increased diastolic and peak Ca(2+)fluorescence (+13+/-1% and +28+/-1%, n=6, P<0.05). Our findings are consistent with a functionally significant role of cAMP/PKA signaling (via cGMP inhibition of PDE3) and SR Ca(2+)in mediating the positive chronotropic effect of NO donors.