Surveillance and screening practices of New England congenital cardiologists for patients after the Fontan operation

INTRODUCTION

Surveillance and management guidelines for Fontan patients are lacking due to the paucity of evidence in the literature of screening efficacy on outcome measures.

METHODS

The Fontan Working Group within the New England Congenital Cardiology Association designed an electronic survey to assess surveillance practices for patients with Fontan procedures among New England congenital cardiologists and to explore variability in screening low-risk vs high-risk Fontan patients across regional programs.

RESULTS

Fifty-six cardiologists representing 12 regional programs responded to the survey, comprising ~40% of the total New England congenital cardiac physicians. The majority of desired testing and consultation was available within 50 miles of the patient's home institution with some limitations of cardiac catheterization and cardiac magnetic resonance imaging availability. Surveillance and screening were less frequent in low-risk Fontan patients compared to high-risk Fontan patients. Counseling practices were similar for both low-risk and high-risk Fontan patients. Aspirin monotherapy was recommended by 82% of providers for low-risk Fontan patients, while anticoagulation regimens were more varied for the high-risk population. Practitioners with ≤15 years of experience were more likely to provide quality of life testing in both low-risk and high-risk Fontan patients. There were no other major differences in testing frequencies by years of practice, quaternary vs nonquaternary care facility, or the number of Fontan patients in a practice.

CONCLUSION

This survey provides insight into regional practices of screening and surveillance of Fontan patients. These data may be used to design future research studies and evidence-based guidelines to streamline the approach to manage these complex patients.

"It Feels Like Being a Real Doctor:" The Virtual Family Approach in Medical Education

This article was migrated. The article was marked as recommended. The majority of health outcomes are determined by social determinants of health (SDOH) while medical care is responsible for as little as 20% of health outcomes. This article is an introduction to the Virtual Family (VF) approach to case based instruction; a novel strategy for addressing SDOH in medical school. The VF theoretical framework is presented and practical considerations and challenges for implementation of the VF approach at three different medical schools are offered. VFs are defined as representations of families or social groups that are not real. "Virtual," in this instance, refers to people or things that do not physically exist. The VF approach allows students and educators to adjust the "lens" of a case's focus to view the relevant determinants. The VF approach is presented as an extension of the virtual patient approach. Theoretical support for the VF approach is argued drawing on principles from modeling and simulation, effective story design, establishing a sense of human presence, serious gaming, visual design, identity leveraging, and flow theory. Challenges and benefits of the approach are described. Measures of efficacy designed to match learning goals are proposed. The VF approach is presented as practical, accessible, economical, and potentially powerful.

Disseminated cytomegalovirus infection complicating active treatment of systemic lupus erythematosus: an emerging problem

Patients with systemic lupus erythematosus (SLE) often require immunosuppression to induce remission of active disease exacerbations. Over the past two decades, treatment modalities for this condition have emerged leading to improved morbidity from disease related outcomes. However, as a result, infection risks and patterns have changed, leading to higher rates of opportunistic infections among this population. We report four cases of cytomegalovirus (CMV) in patients with SLE who received immunosuppressive therapy, including pulse steroids, antimetabolites such as mycophenolate mofetil, and alkylating agents such as cyclophosphamide. We propose that given the rise in prevalence of CMV, there is a need for appropriate screening for this opportunistic pathogen and studies to determine the risks and benefits of prophylactic or preemptive treatment for this virus.

How we developed and piloted an electronic key features examination for the internal medicine clerkship based on a US national curriculum

BACKGROUND

Key features examinations (KFEs) have been used to assess clinical decision making in medical education, yet there are no reports of an online KFE-based on a national curriculum for the internal medicine clerkship. What we did: The authors developed and pilot tested an electronic KFE based on the US Clerkship Directors in Internal Medicine core curriculum. Teams, with expert oversight and peer review, developed key features (KFs) and cases.

EVALUATION

The exam was pilot tested at eight medical schools with 162 third and fourth year medical students, of whom 96 (59.3%) responded to a survey. While most students reported that the exam was more difficult than a multiple choice question exam, 61 (83.3%) students agreed that it reflected problems seen in clinical practice and 51 (69.9%) students reported that it more accurately assessed the ability to make clinical decisions.

CONCLUSIONS

The development of an electronic KFs exam is a time-intensive process. A team approach offers built-in peer review and accountability. Students, although not familiar with this format in the US, recognized it as authentically assessing clinical decision-making for problems commonly seen in the clerkship.

Integration strategies for using virtual patients in clinical clerkships

PURPOSE

To explore students' perceptions of virtual patient use in the clinical clerkship and develop a framework to evaluate effects of different integration strategies on students' satisfaction and perceptions of learning effectiveness with this innovation.

METHOD

A prospective, multiinstitutional study was conducted at six schools' pediatric clerkships to assess the impact of integrating Web-based virtual patient cases on students' perceptions of their learning during 2004-2005 and 2005-2006. Integration strategies were designed to meet the needs of each school, and integration was scored for components of virtual patient use and elimination of other teaching methodologies. A student survey was developed, validated, and administered at the end of the clerkship to 611 students. Data were analyzed using confirmatory factor analysis and structural equation modeling.

RESULTS

A total of 545 students (89%) completed the survey. Overall student satisfaction with the virtual patients was high; students reported that they were more effective than traditional methods. The structural model demonstrated that elimination of other teaching methodologies was directly associated with perceived effectiveness of the integration strategies. A higher use score had a significant negative effect on perceived integration, but a positive effect on perceived knowledge and skills gain. Students' positive perceptions of integration directly affected their satisfaction and perception of the effectiveness of their learning.

CONCLUSIONS

Integration strategies balancing the use of virtual patients with elimination of some other requirements were significantly associated with students' satisfaction and their perceptions of improved knowledge and skills.

Phase I/II study of a novel oral isotype-selective histone deacetylase (HDAC) inhibitor MGCD0103 in combination with azacitidine in patients (pts) with high-risk myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML)

7062

Background: Aberrant DNA methylation and histone acetylation are common in leukemia. The HDAC inhibitor MGCD0103 (0103) and the DNA methyltransferase inhibitor azacitidine (aza); which is approved for all FAB subtypes of MDS, synergize preclinically and both have single-agent activity in MDS and AML. Based on these data, we developed a Phase I/II study of combination aza + 0103 in pts with AML and MDS. Phase I data is presented. Methods: Pts with advanced MDS (=10% marrow blasts), relapsed/refractory or untreated elderly patients with AML were treated with aza 75 mg/m2 SC daily for 7d of each 28-day cycle and 0103 110mg 3x/week starting on day 5. The primary endpoint was determination of the maximum tolerated dose (MTD) of the combination. The phase I portion followed “3+3” model; only 0103 was escalated. Results: Dose levels of 0103 explored were 35, 60, 90, 110 and 135 mg. 24 pts (those having received =1 dose of MGCD0103) have been evaluated; AML=22, MDS=2. Median age 67 (40–85), total cycles=56 (mean=2.3, range=1–11). Dose limiting toxicities observed: vomiting (1/8 pts at 90 mg), nausea & anorexia (2/3 pts at 135 mg), and anorexia (1/6 pts at 110 mg). The MTD of 0103 in the combination was determined to be110 mg. PK characteristics of neither drug was altered by co-administration. 7/9 pts had significant reduction of whole cell HDAC activity during treatment with the combination. Antileukemia activity was documented in 7 pts; 6 of which were among 14 at the 2 most relevant dose levels (90 & 110 mg): 3 CR, 1 PR, and 3 CR without platelet or neutrophil recovery (required for per- protocol response). Of these 7, 4 are ongoing and 3 have been discontinued: 1 to transplant and 2 for SAEs. Conclusions: The Phase I portion of the trial demonstrates that the 0103+aza combination is safe in pts with advanced AML/MDS, and has encouraging biologic & clinical activity. Phase II portion of the study is ongoing at MTD. Molecular studies are ongoing.

No significant financial relationships to disclose.

Cerebral metabolites in HIV-infected children followed for 10 months with 1H-MRS

BACKGROUND

Previous studies have shown that HIV-infected children have abnormal cerebral metabolites, measured by proton MR spectroscopy (1H MRS), but the stability of these measurements over time has not been described in HIV-infected children. The authors recently reported a study of cerebral metabolites in 20 HIV-infected children (6 to 16 years of age); the current study followed 12 of these children (10.0 years +/- 3.7 years) and repeated the MR spectroscopy at 24.1 +/- 3.7 weeks and 42.2 +/- 3.5 weeks following the entry time with repeated neuropsychological testing.

METHODS

1H MR spectra were acquired at 1.5 T (GE Signa, PRESS localization, repetition time = 3,000 msec, echo time = 30 msec). Five brain regions were studied: right frontal white matter, left frontal white matter, right basal ganglia, right hippocampus, and midfrontal gray matter. The concentrations of N-acetylaspartate (NAA), choline (CHO), creatine (CR), and myo-inositol (mI) and the ratio of each metabolite to CR were determined.

RESULTS

There were no changes in the metabolite concentrations or metabolite/CR ratios at the three time periods. Similarly, during this follow-up period, HIV-positive children showed no changes in clinical signs, HIV viral loads, CD4%, or CD4 counts, except for improved spatial memory with repeat testing.

CONCLUSION

In a clinically and neurologically stable group of HIV-infected children, cerebral metabolites were stable over a 10-month time period, suggesting that it is possible to assess changes in cerebral metabolites as a measure of cerebral health, but longer follow-up in a larger sample is needed.

Altered neurometabolite development in HIV-infected children: correlation with neuropsychological tests

BACKGROUND

HIV-infected children have abnormal cerebral metabolites, measured by proton MR spectroscopy ((1)H-MRS), but how these abnormalities relate to brain function is unclear.

METHODS

Metabolite concentrations in five brain regions of 20 HIV-infected and 13 control children were measured, and these findings were correlated with age, log(10) plasma viral load, CD4 count, and neuropsychological scores.

RESULTS

Compared with control subjects, HIV patients had decreased choline concentration [Cho] in left frontal white matter (LFW) (-12%; p = 0.04); those with high viral load (>5,000 HIV RNA copies/mL) had decreased right basal ganglia (RBG) [Cho] (-15%; p = 0.005), and [Cr] (-13%; p = 0.02). Patients with high viral load also had higher [Cho] in the midfrontal gray matter (MFG) (+25%; p = 0.002) and lower myo-inositol [Ins] in the RBG (-18%; p = 0.04) than patients with low HIV viral load. N-Acetyl aspartate concentration ([NAA]) correlated with age in right frontal white matter (RFW) (r = 0.59, p = 0.04), LFW (r = 0.66, p = 0.02), and right hippocampus (RHIP) (r = 0.69, p = 0.02) only in control subjects. In contrast, [Ins] correlated with age in both RFW and LFW (r = 0.71, p = 0.0006; r = 0.65, p = 0.006) only in the HIV patients. Log(10) plasma viral load correlated positively with [Ins] in RFW (r = 0.54, p = 0.02) and [Cho] in MFG (r = 0.49, p = 0.04). Compared with control subjects, HIV patients had poorer spatial memory (p = 0.045) and delayed spatial memory correlated with [Cho] in RHIP (r = 0.68, p = 0.02).

CONCLUSIONS

These data suggest that normal brain development may be affected in children infected with HIV at birth, particularly evidenced by the lack of age-related increases in the neuronal marker [NAA]. Early, aggressive treatment of infants with HIV before development of encephalopathy is warranted.

Levonorgestrel implants (Norplant II) for male contraception clinical trials: combination with transdermal and injectable testosterone

Recent studies demonstrate that combinations of androgens and progestagens are highly effective in the suppression of spermatogenesis in normal volunteers. To test whether progestagen and androgen delivery systems designed to produce steady serum levels will be as effective as other androgen plus progestagen combinations, we compared Norplant II and testosterone (T) transdermal patch to T patch alone on the suppression of spermatogenesis in normal men. Thirty-nine healthy male volunteers (age, 20-45 yr) were randomly assigned to one of two groups. Group 1 (n = 19) received two transdermal T patches daily (Testoderm TTS, each patch designed to deliver about 5 mg/d T) alone, and group 2 (n = 20) received combined Norplant II [Jadelle, four capsules delivering approximately 160 microg/d levonorgestrel (LNG)] plus T patch. Neither of these regimens were very effective, with suppression of spermatogenesis to severe oligozoospermia occurring in less than 60% of subjects. We then expanded the study to include two more groups to determine whether T patch or Norplant II was the main factor causing the inadequate suppression of spermatogenesis. Another 29 subjects were randomized to one of two groups. Group 3 (n = 15) received oral LNG (125 microg/d) plus T patch, and group 4 (n = 14) received Norplant II plus T enanthate (TE) injection (100 mg/wk i.m.). After a pretreatment phase of 4 wk, all subjects received treatment for 24 wk, followed by a recovery period of 12-24 wk. Steady-state serum LNG levels (800-1200 pmol/liter) were achieved from wk 3-24 after Norplant II insertion and decreased rapidly after the removal of the implants at wk 24. Trough serum LNG levels after oral LNG administration were at a comparable range (940-1300 pmol/liter). Azoospermia was achieved in 24%, 35%, 33%, and 93%, and severe oligozoospermia (<1 x 10(6)/ml) developed in 24%, 60%, 42%, and 100% of the subjects in groups 1, 2, 3, and 4, respectively, during treatment phase. All subjects in the Norplant II plus TE groups had persistent sperm concentrations less than 3 x 10(6)/ml from wk 12 until the end of treatment. Concomitant with the marked suppression of spermatogenesis in the Norplant II plus TE group, serum FSH and LH levels were most decreased in this group compared with all other groups. In the T patch-only group, serum SHBG was not suppressed, and total serum T was higher than baseline levels. In the other three groups administered progestagens, serum SHBGs were significantly suppressed, and serum total T remained similar to baseline levels. Serum free T levels were not changed in any group. Except for a suppression of serum high-density lipoprotein cholesterol, there was no significant change in weight, hematocrit, clinical chemistry, or prostate-specific antigen levels in any of the treatment groups. Although more efficacious than T patch alone, Norplant II or oral LNG plus T patch was not as effective in suppressing spermatogenesis to severe oligo- or azoospermia as in previous reports using oral LNG plus TE. This relative lesser efficacy occurred despite the achievement of serum LNG levels by Norplant II that were equivalent to those reported after administration of oral LNG. Substituting the transdermal T delivery system with TE injections resulted in very effective suppression of sperm output. The difference in spermatogenesis suppression of these combined regimens is likely due to less T delivered by the transdermal patch compared with the TE weekly injections. We conclude that Norplant II implants plus TE 100 mg/wk were very efficient in suppressing spermatogenesis to a level acceptable for contraceptive efficacy. This study demonstrates that the dose or route of administration of androgens is critical for sperm suppression in combined androgen-progestagen regimens for hormonal male contraception.

Testosterone dose-response relationships in healthy young men

Testosterone increases muscle mass and strength and regulates other physiological processes, but we do not know whether testosterone effects are dose dependent and whether dose requirements for maintaining various androgen-dependent processes are similar. To determine the effects of graded doses of testosterone on body composition, muscle size, strength, power, sexual and cognitive functions, prostate-specific antigen (PSA), plasma lipids, hemoglobin, and insulin-like growth factor I (IGF-I) levels, 61 eugonadal men, 18-35 yr, were randomized to one of five groups to receive monthly injections of a long-acting gonadotropin-releasing hormone (GnRH) agonist, to suppress endogenous testosterone secretion, and weekly injections of 25, 50, 125, 300, or 600 mg of testosterone enanthate for 20 wk. Energy and protein intakes were standardized. The administration of the GnRH agonist plus graded doses of testosterone resulted in mean nadir testosterone concentrations of 253, 306, 542, 1,345, and 2,370 ng/dl at the 25-, 50-, 125-, 300-, and 600-mg doses, respectively. Fat-free mass increased dose dependently in men receiving 125, 300, or 600 mg of testosterone weekly (change +3.4, 5.2, and 7.9 kg, respectively). The changes in fat-free mass were highly dependent on testosterone dose (P = 0.0001) and correlated with log testosterone concentrations (r = 0.73, P = 0.0001). Changes in leg press strength, leg power, thigh and quadriceps muscle volumes, hemoglobin, and IGF-I were positively correlated with testosterone concentrations, whereas changes in fat mass and plasma high-density lipoprotein (HDL) cholesterol were negatively correlated. Sexual function, visual-spatial cognition and mood, and PSA levels did not change significantly at any dose. We conclude that changes in circulating testosterone concentrations, induced by GnRH agonist and testosterone administration, are associated with testosterone dose- and concentration-dependent changes in fat-free mass, muscle size, strength and power, fat mass, hemoglobin, HDL cholesterol, and IGF-I levels, in conformity with a single linear dose-response relationship. However, different androgen-dependent processes have different testosterone dose-response relationships.

CYP2D6 polymorphism in a Mexican American population

BACKGROUND

Pharmacogenetic data are largely unavailable for Mexican Americans, despite being one of the largest populations in America.

METHODS

The CYP2D6 genotype (n = 349) and dextromethorphan hydroxylation phenotype (n = 285) were studied in 380 Mexican American subjects from Los Angeles County.

RESULTS

The allelic frequency was 22.8% for CYP2D6*2, 10.3% for CYP2D6*4, 7.4% for CYP2D6*10, 2.3% for CYP2D6*5, 1% for CYP2D6*XN (duplication), and <1% for CYP2D6*3 and CYP2D6*17. By using the published antimode for Caucasians, we identified nine subjects as poor metabolizers, an incidence of 3.2%. Of the eight poor metabolizers who were also genotyped, five either were homozygous for the CYP2D6*4 allele (4 cases) or had a combination of CYP2D6*4 and CYP2D6*5 alleles. The mean log(10) dextromethorphan/dextrorphan ratio was -2.47 for those classified as extensive metabolizers. The number of functional alleles among the extensive metabolizers correlated strongly with the phenotype, suggesting a gene-dose effect.

CONCLUSION

Compared with previous reports on Caucasian populations, studies show that Mexican Americans appear to possess a lower rate of CYP2D6*4. Frequencies for the other alleles appear to be less divergent between the two groups. This genotypic pattern might be responsible for the lower rate for the poor metabolizer status, as well as for the faster enzyme activity in the extensive metabolizer subjects that was also reflected in our data.

Health care for Latino children: impact of child and parental birthplace on insurance status and access to health services

OBJECTIVES

This study sought to assess the impact of child and parental birthplace on insurance status and access to health care among Latino children in the United States.

METHODS

A cross-sectional, in-person survey of 376 random households with children aged 1 to 12 years was conducted in a predominantly Latino community. Children's insurance status and access to routine health care were compared among 3 child-parent groups: US born-US born (UU), US born-immigrant (UI), and immigrant-immigrant (II).

RESULTS

Uninsured rates for the 3 groups of children were 10% (UU), 23% (UI), and 64% (II). Rates for lack of access to routine health care were 5% (UU), 12% (UI), and 32% (II).

CONCLUSION

Latino children of immigrant parents are more likely to lack insurance and access to routine health care than are Latino children of US-born parents.

Function of NMDA receptors and persistent sodium channels in a feedback pathway of the electrosensory system

Voltage-dependent amplification of ionotropic glutamatergic excitatory postsynaptic potentials (EPSPs) can, in many vertebrate neurons, be due either to the intrinsic voltage dependence of N-methyl-D-aspartate (NMDA) receptors, or voltage-dependent persistent sodium channels expressed on postsynaptic dendrites or somata. In the electrosensory lateral line lobe (ELL) of the gymnotiform fish Apteronotus leptorhynchus, glutamatergic inputs onto pyramidal cell apical dendrites provide a system where both amplification mechanisms are possible. We have now examined the roles for both NMDA receptors and sodium channels in the control of EPSP amplitude at these synapses. An antibody specific for the A. leptorhynchus NR1 subunit reacted strongly with ELL pyramidal cells and were particularly abundant in the spines of pyramidal cell apical dendrites. We have also shown that NMDA receptors contributed strongly to the late phase of EPSPs evoked by stimulation of the feedback fibers terminating on the apical dendritic spines; further, these EPSPs were voltage dependent. Blockade of NMDA receptors did not, however, eliminate the voltage dependence of these EPSPs. Blockade of somatic sodium channels by local somatic ejection of tetrodotoxin (TTX), or inclusion of QX314 (an intracellular sodium channel blocker) in the recording pipette, reduced the evoked EPSPs and completely eliminated their voltage dependence. We therefore conclude that, in the subthreshold range, persistent sodium currents are the main contributor to voltage-dependent boosting of EPSPs, even when they have a large NMDA receptor component.

Analysis of the CYP2D6 gene polymorphism and enzyme activity in African-Americans in southern California

Despite its importance in drug metabolism and disease susceptibility, CYP2D6 activity and genetic polymorphism have rarely been investigated in African-American populations. In order to bridge this gap, we examined the genotype and phenotype of the enzyme in 154 African-American (AA) and 143 Caucasian (C) normal volunteers. AAs are significantly more likely to possess *17 and *5, but less likely to have *4. Overall, the two groups were similar in their CYP2D6 activity as measured with dextromethorphan as the probe (metabolic ratio 2.21 +/- 0.78 for AAs; 2.11 +/- 0.86 for Cs; t = 1.02, NS). Two of four AAs and six of seven Cs were classified as poor metabolizers and have two nonfunctioning alleles. CYP2D6 activity is determined by *17, *4, *5 and age in AAs (r2 = 0.33, f = 18.8, P < 0.001) and by *4 and *XN in Cs (r2 = 0.14, f = 10.8, P < 0.001). These results support previous findings demonstrating the importance of *17 in determining CYP2D6 activity in AAs.

Effects of transdermal testosterone gel on bone turnover markers and bone mineral density in hypogonadal men

OBJECTIVE

Androgen replacement has been reported to increase bone mineral density (BMD) in hypogonadal men. We studied the effects of 6 months of treatment with a new transdermal testosterone (T) gel preparation on bone turnover markers and BMD.

DESIGN

This was a prospective, randomized, multicentre, parallel clinical trial where 227 hypogonadal men, mean age 51 years (range: 19-68 years) were studied in 16 academic and research institutions in the USA. Subjects were randomized to apply 1% T gel containing 50 or 100 mg T (delivering approximately 5-10 mg T/day) or two T patches (delivering 5 mg T/day) transdermally for 90 days. At day 91, depending on the serum T concentration, the T gel dose was adjusted upward or downward to 75 mg T/day until day 180. No dose adjustment occurred in the T patch group.

MEASUREMENTS

Serum T, free T and oestradiol, bone turnover markers and BMD were measured on days 0, 30, 90 and 180 before and after treatment.

RESULTS

Application of T gel 100 mg/day resulted in serum T concentrations 1.4 and 1.9-fold higher than in the T gel 50 mg/day and the T patch groups, respectively. Proportional increases occurred in serum oestradiol. Urine N-telopeptide/creatinine ratio, a marker for bone resorption, decreased significantly (P = 0.0019) only in the T gel 100 mg/day group. Serum bone osteoblastic activity markers (osteocalcin, procollagen and skeletal alkaline phosphatase) increased significantly during the first 90 days of treatment without intergroup differences but declined to baseline thereafter. BMD increased significantly both in the hip (+1.1 +/- 0.3%) and spine (+2.2 +/- 0.5%) only in the T gel 100 mg/day group (P = 0.0001).

CONCLUSIONS

Transdermal testosterone gel application for 6 months decreased bone resorption markers and increased osteoblastic activity markers for a short period, which resulted in a small but significant increase in BMD. Ongoing long-term studies should answer whether the observed increases in BMD are sustained or continue to be dependent on the dose of testosterone administered.

Effects of contingent television on physical activity and television viewing in obese children

OBJECTIVE

Elevated television (TV) viewing and physical inactivity promote obesity in children. Thus, changes in physical activity and sedentary behavior seem critical to treating childhood obesity. PRESENT STUDY: Using a randomized, 2-arm design, this pilot study tested the effects of contingent TV on physical activity and TV viewing in 10 obese children. TV viewing was contingent on pedaling a stationary cycle ergometer for experimental participants but was not contingent on pedaling for control participants. The study was conducted over 12 weeks, including a 2-week baseline period.

RESULTS

Multivariate analyses indicated that the intervention significantly increased pedaling and reduced TV-viewing time. During the treatment phase, the experimental group pedaled 64.4 minutes per week on average, compared with 8.3 minutes by controls. The experimental group watched 1.6 hours of TV per week on average, compared with 21.0 hours per week on average by controls during this phase. Secondary analyses indicated that the experimental group showed significantly greater reductions in total body fat and percent leg fat. Total pedaling time during intervention correlated with greater reductions in percent body fat (r = -0.68).

CONCLUSIONS

Contingencies in the home environment can be arranged to modify physical activity and TV viewing and may have a role in treating childhood obesity. Contingent TV may be one method to help achieve this goal.

Subtractive and divisive inhibition: effect of voltage-dependent inhibitory conductances and noise

The influence of voltage-dependent inhibitory conductances on firing rate versus input current (f-I) curves is studied using simulations from a new compartmental model of a pyramidal cell of the weakly electric fish Apteronotus leptorhynchus. The voltage dependence of shunting-type inhibition enhances the subtractive effect of inhibition on f-I curves previously demonstrated in Holt and Koch (1997) for the voltage-independent case. This increased effectiveness is explained using the behavior of the average subthreshold voltage with input current and, in particular, the nonlinearity of Ohm's law in the subthreshold regime. Our simulations also reveal, for both voltage-dependent and -independent inhibitory conductances, a divisive inhibition regime at low frequencies (f < 40 Hz). This regime, dependent on stochastic inhibitory synaptic input and a coupling of inhibitory strength and variance, gives way to subtractive inhibition at higher-output frequencies (f > 40 Hz). A simple leaky integrate-and-fire type model that incorporates the voltage dependence supports the results from our full ionic simulations.

Long-term pharmacokinetics of transdermal testosterone gel in hypogonadal men

Transdermal delivery of testosterone (T) represents an effective alternative to injectable androgens. Transdermal T patches normalize serum T levels and reverse the symptoms of androgen deficiency in hypogonadal men. However, the acceptance of the closed system T patches has been limited by skin irritation and/or lack of adherence. T gels have been proposed as delivery modes that minimize these problems. In this study we examined the pharmacokinetic profiles after 1, 30, 90, and 180 days of daily application of 2 doses of T gel (50 and 100 mg T in 5 and 10 g gel, delivering 5 and 10 mg T/day, respectively) and a permeation-enhanced T patch (2 patches delivering 5 mg T/day) in 227 hypogonadal men. This new 1% hydroalcoholic T gel formulation when applied to the upper arms, shoulders, and abdomen dried within a few minutes, and about 9-14% of the T applied was bioavailable. After 90 days of T gel treatment, the dose was titrated up (50 mg to 75 mg) or down (100 mg to 75 mg) if the preapplication serum T levels were outside the normal adult male range. Serum T rose rapidly into the normal adult male range on day 1 with the first T gel or patch application. Our previous study showed that steady state T levels were achieved 48-72 h after first application of the gel. The pharmacokinetic parameters for serum total and free T were very similar on days 30, 90, and 180 in all treatment groups. After repeated daily application of the T formulations for 180 days, the average serum T level over the 24-h sampling period (C(avg)) was highest in the 100 mg T gel group (1.4- and 1.9-fold higher than the C(avg) in the 50 mg T gel and T patch groups, respectively). Mean serum steady state T levels remained stable over the 180 days of T gel application. Upward dose adjustment from T gel 50 to 75 mg/day did not significantly increase the C(avg), whereas downward dose adjustment from 100 to 75 mg/day reduced serum T levels to the normal range for most patients. Serum free T levels paralleled those of serum total T, and the percent free T was not changed with transdermal T preparations. The serum dihydrotestosterone C(avg) rose 1.3-fold above baseline after T patch application, but was more significantly increased by 3.6- and 4.6-fold with T gel 50 and 100 mg/day, respectively, resulting in a small, but significant, increase in the serum dihydrotestosterone/T ratios in the two T gel groups. Serum estradiol rose, and serum LH and FSH levels were suppressed proportionately with serum T in all study groups; serum sex hormone-binding globulin showed small decreases that were significant only in the 100 mg T gel group. We conclude that transdermal T gel application can efficiently and rapidly increase serum T and free T levels in hypogonadal men to within the normal range. Transdermal T gel provided flexibility in dosing with little skin irritation and a low discontinuation rate.

Hypopituitarism following traumatic brain injury and aneurysmal subarachnoid hemorrhage: a preliminary report

OBJECT

Recognition of pituitary hormonal insufficiencies after head injury and aneurysmal subarachnoid hemorrhage (SAH) may be important, especially given that hypopituitarism-related neurobehavioral problems are typically alleviated by hormone replacement. In this prospective study the authors sought to determine the rate and risk factors of pituitary dysfunction after head injury and SAH in patients at least 3 months after insult.

METHODS

Patients underwent dynamic anterior and posterior pituitary function testing. Results of the tests were compared with those of 18 age-, sex-, and body mass index-matched healthy volunteers. The 22 head-injured patients included 18 men and four women (mean age 28+/-10 years at the time of injury) with initial Glasgow Coma Scale (GCS) scores of 3 to 15. Eight patients (36.4%) had a subnormal response in at least one hormonal axis. Four were growth hormone (GH) deficient. Five patients (four men, all with normal testosterone levels, and one woman with a low estradiol level) exhibited an inadequate gonadotroph response. One patient had both GH and thyrotroph deficiency and another had both GH deficiency and borderline cortisol deficiency. At the time of injury, all eight patients with pituitary dysfunction had an initial GCS score of 10 or less and, compared with the 14 patients without dysfunction, were more likely to have had diffuse swelling, seen on initial computerized tomography scans (p < 0.05), and to have sustained a hypotensive or hypoxic insult (p = 0.07). Of two patients with SAH who were studied (Hunt and Hess Grade IV) both had GH deficiency.

CONCLUSIONS

From this preliminary study, some degree of hypopituitarism appears to occur in approximately 40% of patients with moderate or severe head injury, with GH and gonadotroph deficiencies being most common. A high degree of injury severity and secondary cerebral insults are likely risk factors for hypopituitarism. Pituitary dysfunction also occurs in patients with poor-grade aneurysms. Postacute pituitary function testing may be warranted in most patients with moderate or severe head injury, particularly those with diffuse brain swelling and those sustaining hypotensive or hypoxic insults. The neurobehavioral effects of GH replacement in patients suffering from head injury or SAH warrant further study.

Postnatal thyroxine supplementation in infants less than 32 weeks' gestation: effects on pulmonary morbidity

OBJECTIVE

Transient hypothyroxinemia in premature newborns has been linked with poor neonatal outcomes. We designed this study to evaluate the effects of early thyroxine (T4) administration in the premature infant.

STUDY DESIGN

A total of 49 newborns less than 32 weeks' gestation, were randomized in a double-blind, placebo-controlled trial. Within the first 48 hours of life, T4 (10 or 20 micrograms/kg; intravenous or through nasogastric tube, respectively) was administered for a total of 21 days. Chronic lung disease, the primary outcome variable, was defined by oxygen dependency at 28 days of life.

RESULTS

The incidence of chronic lung disease, death, grade III or IV intraventricular hemorrhage, periventricular leukomalacia, and sepsis was not different in the placebo and treated groups.

CONCLUSION

Early T4 supplementation in preterm newborns less than 32 weeks' gestation does not decrease the incidence of chronic lung disease or other complications of prematurity.

Transdermal testosterone gel improves sexual function, mood, muscle strength, and body composition parameters in hypogonadal men

Testosterone (T) therapy for hypogonadal men should correct the clinical abnormalities of T deficiency, including improvement of sexual function, increase in muscle mass and strength, and decrease in fat mass, with minimal adverse effects. We have shown that administration of a new transdermal T gel formulation to hypogonadal men provided dose proportional increases in serum T levels to the normal adult male range. We now report the effects of 180 days of treatment with this 1% T gel preparation (50 or 100 mg/day, contained in 5 or 10 g gel, respectively) compared to those of a permeation-enhanced T patch (5 mg/day) on defined efficacy parameters in 227 hypogonadal men. In the T gel groups, the T dose was adjusted up or down to 75 mg/day (contained in 7.5 g gel) on day 90 if serum T concentrations were below or above the normal male range. No dose adjustment was made with the T patch group. Sexual function and mood changes were monitored by questionnaire, body composition was determined by dual energy x-ray absorptiometry, and muscle strength was measured by the one repetitive maximum technique on bench and leg press exercises. Sexual function and mood improved maximally on day 30 of treatment, without differences across groups, and showed no further improvement with continuation of treatment. Mean muscle strength in the leg press exercise increased by 11 to 13 kg in all treatment groups by 90 days and did not improve further at 180 days of treatment. Moderate increases were also observed in arm/chest muscle strength. At 90 days of treatment, lean body mass increased more in the 100 mg/day T gel group (2.74 +/- 0.28 kg; P = 0.0002) than in the 50 mg/day T gel (1.28 +/- 0.32 kg) and T patch groups (1.20 +/- 0.26 kg). Fat mass and percent fat were not significantly decreased in the T patch group, but showed decreases in the T gel groups (50 mg/day, -0.90 +/- 0.32 kg; 100 mg/day, - 1.05 +/- 0.22 kg). The increase in lean mass and the decrease in fat mass were correlated with the changes in average serum T levels attained after transdermal T replacement. These beneficial effects of T replacement were accompanied by the anticipated increases in hematocrit and hemoglobin but without significant changes in the lipid profile. The increase in mean serum prostate-specific antigen levels (within the normal range) was correlated with serum levels of T. The greatest increases were noted in the 100 mg/day T gel group. Skin irritation was reported in 5.5% of subjects treated with T gel and in 66% of subjects in the permeation-enhanced T patch group. We conclude that T gel replacement improved sexual function and mood, increased lean mass and muscle strength (principally in the legs), and decreased fat mass in hypogonadal men with less skin irritation and discontinuation compared with the recommended dose of the permeation-enhanced T patch.

Pharmacokinetics of transdermal testosterone gel in hypogonadal men: application of gel at one site versus four sites: a General Clinical Research Center Study

Testosterone (T) in a hydroalcoholic gel has been developed as an effective and convenient open system for transdermal delivery of the hormone to men. Because the gel can be applied either to small or large areas of skin, it was important to assess whether the skin surface area on which the gel was applied was an important determinant of serum T levels. To answer this question, the pharmacokinetics of a transdermal 1% hydroalcoholic gel preparation of T was studied in nine hypogonadal men. The subjects applied in random order a 25-mg metered dose of T gel either four times at one site (left arm/shoulder) or at four different sites (left and right arms/shoulders and left and right abdomen) once daily (6-8 min) for 7 consecutive days. After 7 days of washout, each subject was then crossed over to the opposite regimen for another 7 days of treatment. Serum samples were collected for measurements of T, 5alpha dihydrotestosterone (DHT), and estradiol before, during (days 1, 2, 3, 5, and 7), and after (days 8, 9, 11, 13, and 15) application of T gel. Multiple blood samples were drawn on the 1st and 7th day after gel application; single samples were obtained just before the next T gel application on other days (24 h after the previous gel application). The T gel dried in less than 5 min, left no residue, and produced no skin irritation in any of the subjects. Mean serum T levels, irrespective of application at one site or four sites followed the same pattern: rising to 2- to 3- and 4- to 5-fold above baseline at 0.5 and 24 h after first application, respectively. Thereafter, serum T levels reached steady state and remained at 4- to 5-fold above baseline (at the upper limit of the normal adult range) for the duration of gel application and returned to baseline within 4 days after stopping application. The application of T gel at four sites (application skin area approximately four times that of one site) resulted in a mean area under the curve (AUC0-24h) for serum T levels on the 7th day (868 +/- 72 nmol*h/L, mean +/- SEM), which was 23% higher but not significantly different (P = 0.06) than repeated application at one site (706 +/- 59 nmol*h/L). This could be due to the limited number of subjects studied (n = 9). Mean serum DHT levels followed the same pattern as serum T, achieving steady-state levels by 2 days. The mean concentration of serum DHT on the 7th day was significantly higher after application at four sites (9.15 +/- 1.26 nmol/L, P < 0.05) than at one site (6.9 +/- 0.77 nmol/L). These serum DHT levels were at or above the normal adult male range. Serum DHT:T ratio was not significantly altered by T gel application. Serum estradiol levels followed the same pattern as serum T and showed no significant difference between the one- or four-site application. We conclude that transdermal daily application of 100 mg T gel resulted in similar steady levels of serum T. The surface area of the skin to which the gel was applied had only a modest impact on serum T and DHT levels. Mean serum levels of T and DHT was higher by 23% and 33%, respectively, despite application of the gel to four times the skin area in the four sites compared with the one site group. Because of the greater dosage flexibility provided, hydroalcoholic T gel application over multiple sites seems to be an effective and nonskin-irritating method of transdermal T delivery for hypogonadal men. Dose-ranging studies are required to determine dosage regimens for T gel application as a replacement therapy in hypogonadal men.

Testosterone replacement and resistance exercise in HIV-infected men with weight loss and low testosterone levels

CONTEXT

Previous studies of testosterone supplementation in HIV-infected men failed to demonstrate improvement in muscle strength. The effects of resistance exercise combined with testosterone supplementation in HIV-infected men are unknown.

OBJECTIVE

To determine the effects of testosterone replacement with and without resistance exercise on muscle strength and body composition in HIV-infected men with low testosterone levels and weight loss.

DESIGN AND SETTING

Placebo-controlled, double-blind, randomized clinical trial conducted from September 1995 to July 1998 at a general clinical research center.

PARTICIPANTS

Sixty-one HIV-infected men aged 18 to 50 years with serum testosterone levels of less than 12.1 nmol/L (349 ng/dL) and weight loss of 5% or more in the previous 6 months, 49 of whom completed the study.

INTERVENTIONS

Participants were randomly assigned to 1 of 4 groups: placebo, no exercise (n = 14); testosterone enanthate (100 mg/wk intramuscularly), no exercise (n = 17); placebo and exercise (n = 15); or testosterone and exercise (n = 15). Treatment duration was 16 weeks.

MAIN OUTCOME MEASURES

Changes in muscle strength, body weight, thigh muscle volume, and lean body mass compared among the 4 treatment groups.

RESULTS

Body weight increased significantly by 2.6 kg (P<.001) in men receiving testosterone alone and by 2.2 kg (P = .02) in men who exercised alone but did not change in men receiving placebo alone (-0.5 kg; P = .55) or testosterone and exercise (0.7 kg; P = .08). Men treated with testosterone alone, exercise alone, or both experienced significant increases in maximum voluntary muscle strength in leg press (range, 22%-30%), leg curls (range, 18%-36%), bench press (range, 19%-33%), and latissimus pulls (range, 17%-33%). Gains in strength in all exercise categories were greater in men assigned to the testosterone-exercise group or to the exercise-alone group than in those assigned to the placebo-alone group. There was a greater increase in thigh muscle volume in men receiving testosterone alone (mean change, 40 cm3; P<.001 vs zero change) or exercise alone (62 cm3; P = .003) than in men receiving placebo alone (5 cm3; P = .70). Average lean body mass increased by 2.3 kg (P = .004) and 2.6 kg (P<.001), respectively, in men who received testosterone alone or testosterone and exercise but did not change in men receiving placebo alone (0.9 kg; P = .21). Hemoglobin levels increased in men receiving testosterone but not in those receiving placebo.

CONCLUSION

Our data suggest that testosterone and resistance exercise promote gains in body weight, muscle mass, muscle strength, and lean body mass in HIV-infected men with weight loss and low testosterone levels. Testosterone and exercise together did not produce greater gains than either intervention alone.

Neuropsychological patterns in right versus left frontotemporal dementia

Patients with frontotemporal dementia (FTD) often present with an asymmetric left or right-sided anterior cerebral perfusion abnormality that is associated with differential behavioral symptoms. However, whether patients with primarily right versus left FTD also have unique neuropsychological characteristics has not been previously investigated. Comparisons of 11 patients with right-sided FTD and 11 with left FTD indicated that the 2 patient groups showed relatively distinct cognitive profiles. Patients with right FTD exhibited relatively worse performance on PIQ than VIQ, and on select nonverbal executive tasks relative to their verbal analogs (e.g., design fluency < word generation; Picture Arrangement < word sequencing). In contrast, patients with left FTD showed the opposite pattern. In addition, the 2 patient groups differed on several absolute test scores; patients with right FTD demonstrated more errors and perseverative responses, and worse percent conceptual level responses, on the Wisconsin Card Sorting Test, while the left FTD patients obtained significantly worse scores on the Boston Naming Test, and Stroop word reading and color naming. Verbal and nonverbal memory, mental speed, visual perceptual-constructional skill, and IQ subtest scaled scores did not significantly differ between groups. These data indicate that FTD should not be viewed as a unitary disorder, and that neuropsychological testing holds promise for the differential diagnosis of right versus left FTD.

Glucose entrainment of high-frequency plasma insulin oscillations in control and type 2 diabetic subjects

Regular high-frequency oscillations of insulin secretion are characteristic of normal beta-cell function. These oscillations are easily entrainable to an exogenous rhythm by small changes in glucose concentration in vitro. We tested whether high-frequency insulin oscillations in vivo would also be entrainable by glucose and whether a lack of entrainment would characterize the diabetic beta-cell. We tested 13 control subjects and 11 patients with type 2 diabetes. Subjects underwent serial blood sampling at 1-min intervals for 60-120 min in the basal state or with small (15 mg/kg) boluses of glucose injected intravenously at exact 29-min intervals. Time series analysis was carried out using spectral analysis. Oscillations of basal plasma glucose concentrations were observed in both control and type 2 diabetic subjects, with a mean period of 11.3 +/- 3.1 and 11.6 +/- 2.0 min, respectively. These oscillations were entrained to mean periods of 15.0 +/- 0.6 and 14.2 +/- 0.9 min, respectively, by exogenous glucose. Regular high-frequency insulin oscillations were observed in control subjects; the mean period of basal plasma insulin oscillations was 10.7 +/- 1.2 min and was entrained to exogenously injected glucose, with a period of 15.2 +/- 0.1 min. In contrast, in the type 2 diabetic subjects, spontaneous insulin oscillations were unchanged by the glucose rhythm; the mean periods were 10.0 +/- 1.0 min during the basal period, and 10.1 +/- 0.0 min during glucose injections. These results demonstrate that spontaneous high-frequency insulin oscillations can be successfully entrained by glucose in control subjects. However, these oscillations in type 2 diabetic subjects are not similarly entrained. We conclude that loss of entrainment of spontaneous high-frequency insulin oscillations in type 2 diabetes is a highly sensitive manifestation of beta-cell secretory dysfunction.

Counterregulatory hormones oscillate during steady-state hypoglycemia

During hypoglycemia, the magnitude of the counterregulatory response depends on the extent of plasma glucose reduction. However, our clinical observations during steady-state hypoglycemia indicate that symptom severity can change independently of plasma glucose concentrations, i.e., symptoms appeared to fluctuate despite stable glucose levels. This study was therefore designed to test the hypothesis that hormonal and symptomatic responses to hypoglycemia are pulsatile. Seven healthy subjects had serial blood sampling at 3-min intervals during 90 min of insulin-induced hypoglycemia. Mean +/- SE plasma glucose levels plateaued at 62 +/- 3 mg/dl. Counterregulatory hormones were significantly elevated (P < 0.05-0. 01, except norepinephrine) and strikingly pulsatile. Cluster analysis revealed pulses of large magnitude in plasma glucagon, epinephrine, and norepinephrine concentrations. Amplitudes were, respectively, 72 +/- 4, 64 +/- 8, and 48 +/- 3% of the mean. Interpeak intervals were 27 +/- 7, 19 +/- 4, and 25 +/- 5 min, respectively. Symptom score and cardiovascular responses were also pulsatile; their peaks were found to coincide with epinephrine peaks. We conclude that hormonal and symptomatic counterregulation in hypoglycemia, while critically driven by plasma glucose levels, is also influenced by an endogenous pulsatility that exists despite steady-state glucose concentrations.

Suppression of spermatogenesis in man induced by Nal-Glu gonadotropin releasing hormone antagonist and testosterone enanthate (TE) is maintained by TE alone

GnRH antagonists plus testosterone (T) suppress LH and FSH levels and inhibit spermatogenesis to azoospermia or severe oligozoospermia. High-dose T treatment alone has been shown to be an effective male contraceptive (contraceptive efficacy rate of 1.4 per 100 person yr). Combined GnRH antagonist and T induces azoospermia more rapidly and at a higher incidence than T alone; this combination has therefore been proposed as a prototype male contraceptive. However, because GnRH antagonists are expensive to synthesize and difficult to deliver, it would be desirable to rapidly suppress sperm counts to low levels with GnRH antagonist plus T and maintain azoospermia or severe oligozoospermia with T alone. In this study, 15 healthy men (age 21-41 yr) with normal semen analyses were treated with T enanthate (TE) 100 mg im/week plus 10 mg Nal-Glu GnRH antagonist sc daily for 12 weeks to induce azoospermia or severe oligozoospermia. At 12-16 weeks, 10 of 15 subjects had zero sperm counts, and 14 of 15 had sperm counts less than 3 x 10(6)/mL. The 14 who were suppressed on combined treatment were maintained on TE alone (100 mg/week im) for an additional 20 weeks. Thirteen of 14 subjects in the TE alone phase had sperm counts maintained at less than 3 x 10(6)/mL for 20 weeks. Ten remained persistently azoospermic or had sperm concentration of 0.1 x 10(6)/mL once during maintenance. Mean LH and FSH levels in the subjects were suppressed to 0.4+/-0.2 IU/L and 0.5+/-0.2 IU/L in the induction phase, which was maintained in the maintenance phase. The 1 subject who failed to suppress sperm counts during induction had serum LH and FSH reduced to 0.3 and 0.5 IU/L, respectively. The subject who failed to maintenance had LH and FSH suppressed to 1.0 and 0.2 IU/L, respectively, during the induction phase but these rose to 1.6 and 2.1 IU/L, respectively, during maintenance. Failure to suppress or maintain low sperm counts may be related to incomplete suppression of serum LH and FSH levels. We conclude that sperm counts suppressed with GnRH antagonist plus T can be maintained with relatively low dose TE treatment alone. This concept should be explored further in the development of effective, safe, and affordable hormonal male contraceptives.

Different training procedures recruit either one or two critical periods for contextual memory consolidation, each of which requires protein synthesis and PKA

We have used a combined genetic and pharmacological approach to define the time course of the requirement for protein kinase A (PKA) and protein synthesis in long-term memory for contextual fear conditioning in mice. The time course of amnesia in transgenic mice that express R(AB) and have genetically reduced PKA activity in the hippocampus parallels that observed both in mice treated with inhibitors of PKA and mice treated with inhibitors of protein synthesis. This PKA- and protein synthesis-dependent memory develops between 1 hr and 3 hr after training. By injecting the protein synthesis inhibitor anisomycin or the PKA inhibitor Rp-cAMPs at various times after training, we find that depending on the nature of training, contextual memory has either one or two brief consolidation periods requiring synthesis of new proteins, and each of these also requires PKA. Weak training shows two time periods of sensitivity to inhibitors of protein synthesis and PKA, whereas stronger training exhibits only one. These studies underscore the parallel dependence of long-term contextual memory on protein synthesis and PKA and suggest that different training protocols may recruit a common signaling pathway in distinct ways.

Comparative pharmacokinetics of three doses of percutaneous dihydrotestosterone gel in healthy elderly men--a clinical research center study

Twenty-five men, 60-80 yr old, participated in a pharmacokinetic study to compare three doses (16, 32, and 64 mg/day, n = 8 or 9 in each group) of 5alpha-dihydrotestosterone (DHT) gel (0.7% hydroalcoholic gel with 2.3 g gel delivering 16 mg DHT) applied daily over one upper arm (16 mg); both arms and shoulders (32 mg); and bilateral arms, shoulders, and upper abdomen (64 mg), respectively. Multiple blood samples for the pharmacokinetic profile for DHT and testosterone (T) were drawn over a 24-h period before application, after first application, and after 14 days of daily application of DHT gel. Additional blood samples for DHT, T, and estradiol were obtained 24 h after application on days 3, 5, 7, and 11 and after discontinuation of DHT gel for 3, 5, 7, and 14 days (days 17, 19, 21, and 28 after first instituting treatment). No skin irritation was observed in any of the subjects. Before treatment, mean serum DHT and T levels were not different among the three dose groups. The serum DHT levels increased gradually after gel application on the first day, reaching a plateau between 12-18 h. During the 14 days of daily application of DHT gel, the mean baseline DHT levels reached steady state by day 2 or 3 and were elevated considerably above baseline. Mean serum DHT levels varied between 8-11, 12-17, and 14-24 nmol/L in the 16-, 32-, and 64-mg groups, respectively. The area under curve (AUC) of serum DHT levels over 24 h on day 14 were 6.0-, 6.9-, and 16.1-fold above pretreatment levels for the three doses. Concomitant with the increase in serum DHT levels, the AUC produced by endogenous serum T levels decreased to 75, 56, and 36% of baseline after 14 days of 16, 32, and 64 mg/day DHT gel. Similar patterns of decreases in AUC of serum estradiol levels were found. The calculated mean total androgen levels (T + DHT) rose with DHT gel application in all groups (P < 0.0001) on both days 1 and 14. We conclude that the three doses of DHT gel tested might provide adequate androgen replacement in hypogonadal men at the low, middle, and high physiological androgen (T + DHT) range.

Effects of lead exposure on GnRH and LH secretion in male rats: response to castration and alpha-methyl-p-tyrosine (AMPT) challenge

Animal and clinical studies suggest that lead exposure disrupts the hypothalamic-pituitary axis. To define more precisely the toxic action of lead on the hypothalamic-pituitary unit, a series of in vivo and in vitro experiments were performed. The first experiment was designed to determine whether lead exposure exerts an inhibitory effect on GnRH secretion as reflected by an enhanced inhibition of luteinizing hormone (LH) secretion in response to the tyrosine hydroxylase inhibitor methyl-p-tyrosine (AMPT). In the control animals, the AMPT dose had no significant effect on LH secretion, whereas LH fell significantly in the lead-treated animals. In experiments designed to evaluate the effects of lead exposure on the pattern of pulsatile release of gonadotropins castrated control and lead-dosed animals were cannulated, and serial blood sampling was performed. Baseline LH and follicle-stimulating hormone values were not statistically different between the control and lead-treated group. There were no significant differences noted in pulsatile patterns when the data were analyzed as groups. Pituitary cells harvested from lead-treated animals released significantly more LH that did the control animals. These data are consistent with the hypothesis that the signals between the hypothalamus and pituitary gland are disrupted by lead exposure in the intact animal. However, the lead-exposed castrated rat's hypothalamic-pituitary unit is able to adapt to the toxic effects of lead.

A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American EGb Study Group

CONTEXT

EGb 761 is a particular extract of Ginkgo biloba used in Europe to alleviate symptoms associated with numerous cognitive disorders. Its use in dementias is based on positive results from only a few controlled clinical trials, most of which did not include standard assessments of cognition and behavior.

OBJECTIVE

To assess the efficacy and safety of EGb in Alzheimer disease and multi-infarct dementia.

DESIGN

A 52-week, randomized double-blind, placebo-controlled, parallel-group, multicenter study.

PATIENTS

Mildly to severely demented outpatients with Alzheimer disease or multi-infarct dementia, without other significant medical conditions.

INTERVENTION

Patients assigned randomly to treatment with EGb (120 mg/d) or placebo. Safety, compliance, and drug dispensation were monitored every 3 months with complete outcome evaluation at 12, 26, and 52 weeks.

PRIMARY OUTCOME MEASURES

Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), Geriatric Evaluation by Relative's Rating Instrument (GERRI), and Clinical Global Impression of Change (CGIC).

RESULTS

From 309 patients included in an intent-to-treat analysis, 202 provided evaluable data for the 52-week end point analysis. In the intent-to-treat analysis, the EGbgroup had an ADAS-Cog score 1.4 points better than the placebo group (P=.04) and a GERRI score 0.14 points better than the placebo group (P=.004). The same patterns were observed with the evaluable data set in which 27% of patients treated with EGb achieved at least a 4-point improvement on the ADAS-Cog, compared with 14% taking placebo (P=.005); on the GERRI, 37% were considered improved with EGb, compared with 23% taking placebo (P=.003). No difference was seen in the CGIC. Regarding the safety profile of EGb, no significant differences compared with placebo were observed in the number of patients reporting adverse events or in the incidence and severity of these events.

CONCLUSIONS

EGb was safe and appears capable of stabilizing and, in a substantial number of cases, improving the cognitive performance and the social functioning of demented patients for 6 months to 1 year. Although modest, the changes induced by EGb were objectively measured by the ADAS-Cog and were of sufficient magnitude to be recognized by the caregivers in the GERRI.

Erratic oscillatory characteristics of plasma insulin concentrations in patients with insulinoma: mechanism for unpredictable hypoglycemia

Patients with insulin-producing tumors may have hypoglycemic symptoms at unpredictable times. This study evaluated whether plasma insulin oscillations, known to occur in normal individuals but not explored in patients with insulinomas, could be an underlying mechanism for such events. Nine normal subjects and five patients with proven insulinomas were studied in the fasting state. Serial sampling of arterialized blood over 80-100 min, at 2- or 3-min intervals was performed. In normal subjects, mean plasma glucose and insulin concentrations were 5.3 +/- 0.1 mmol/L and 58 +/- 9 pmol/L, respectively. Regular, low-amplitude plasma insulin oscillations were observed, with a period of 10-17 min. The subjects with insulinomas had lower mean plasma glucose and higher insulin concentrations than controls, 3.6 +/- 0.3 mmol/L (P = 0.01) and 150 +/- 42 pmol/L (P = 0.01), respectively. They also had insulin oscillations that appeared unstable as a result of variability in duration and amplitude compared with controls. The insulin pulses were irregular, and interpeak intervals varied between 4-54 min in different subjects; in some subjects, the amplitude was also variable, with sudden spontaneous pulses as high as 565 pmol/L, with an associated glucose decrement. We conclude that large spontaneous bursts of insulin secretion occur in patients with insulinomas as part of an erratic pattern of oscillatory insulin secretion, and these can account for unpredictable occurrences of hypoglycemia.

Effect of increased scrotal temperature on sperm production in normal men

OBJECTIVE

To determine whether application of polyester-lined athletic supports to bring the testes closer to the abdomen increases scrotal temperature and decreases sperm production.

DESIGN

Prospective clinical study.

SETTING

University academic medical center.

PATIENT(S)

Twenty-one healthy male volunteers.

INTERVENTION(S)

The study consisted of a pretreatment period of 6 weeks, a treatment phase of 52 weeks, and a recovery phase until return to normal sperm production. During the treatment phase, the men wore polyester-lined athletic supports (single layer, double layer, or double layer impregnated with aluminum) throughout the day.

MAIN OUTCOME MEASURE(S)

Semen parameters and sperm function tests.

RESULT(S)

In all three groups of subjects, scrotal temperature was consistently increased by 0.8 to 1 degree C while the subjects were wearing the athletic supports. Mean sperm concentration; sperm motility, morphology, and viability; sperm hyperactivation; and ability of spermatozoa to penetrate zone-free hamster oocytes were not affected by the increase in scrotal temperature.

CONCLUSION(S)

The increase in scrotal temperature induced by polyester-lined athletic supports was insufficient to cause significant suppression of spermatogenesis or alteration of sperm function.