Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p- paternal transmission cohort. We also discovered Ube3am-/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am-/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p- did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS.

Adverse Childhood Experiences and Health and Wellness Outcomes among Black Men Who Have Sex with Men

Black men who have sex with men (BMSM) are a population at the intersection of two minority statuses-racial minority and sexual minority. Membership in either group, compared to white or heterosexual group membership, may increase one's risk of negative childhood and adult experiences. Baseline data from an HIV intervention efficacy trial (the Black Men Evolving Study) were used to explore the prevalence of adverse childhood experiences (ACEs) among 536 BMSM and associations between ACEs and adult mental and physical health outcomes. Overall, the prevalence of ACEs was high among this sample of BMSM with almost 90% experiencing at least one ACE. Findings revealed that ACE score was significantly associated with adult mental health (AOR = 1.21, 95% CI [1.12, 1.30]), but not with adult physical health. All ACEs were significantly associated with mental health, but only physical neglect and household substance abuse were significantly associated with physical health (AOR = 1.69, 95% CI [1.02, 2.74] and AOR = 1.57, 95% CI [1.03, 2.40], respectively). The findings support the need for interventions targeting improved adult health outcomes, particularly for minority groups, to consider the impact of early adversity on health and wellness.

The effect of time-of-day dosing on the pharmacokinetics and pharmacodynamics of dexlansoprazole MR: evidence for dosing flexibility with a Dual Delayed Release proton pump inhibitor

BACKGROUND

Dexlansoprazole MR is a Dual Delayed Release proton pump inhibitor formulated to extend the duration of acid suppression.

AIM

To evaluate the pharmacokinetics and pharmacodynamics of dexlansoprazole MR dosed before 4 different meal times.

METHODS

In this randomized, open-label, four-way crossover study, 48 healthy subjects received dexlansoprazole MR 60 mg once daily 30 min before breakfast, lunch, dinner or an evening snack. Pharmacokinetics of dexlansoprazole MR and intragastric pH were assessed over a 24-h postdose interval on day 5 for each regimen.

RESULTS

Absorption was delayed when dexlansoprazole MR was administered before each regimen relative to breakfast; however, systemic exposures of dexlansoprazole at all regimens were bioequivalent. There were no statistically significant differences in mean 24-h intragastric pH between dosing before dinner or an evening snack vs. breakfast; however, there was a small (0.2), but statistically significant difference between lunch and breakfast. There was a statistically significant difference of 7 percentage points in the percentage of time intragastric pH was >4 for the snack regimen relative to the breakfast regimen, but there were no statistically significant differences between lunch or dinner compared with breakfast.

CONCLUSION

Dexlansoprazole MR provides comparable acid control when administered at different times of the day.

Lactational coumestrol exposure increases ovarian apoptosis in adult rats

This study is the first to examine the increased apoptosis in the adult rat ovary after lactational exposure to coumestrol (COU), a potent phytoestrogen. Lactating dams were gavaged at doses of 0.01, 0.1, 1, and 10 mg/kg COU during the lactation period and the reproductive effects of female pups were investigated in young adults. Rats were sacrificed at postnatal days (PND) 81-84. Ovarian weights were reduced significantly at 0.1 and 1.0 mg/kg COU. The reduction in the ovarian weight occurred in parallel with an increase in the apoptosis at PND 135-140. A marked dose-dependent increase in the expressions of active caspase-3 and -7 was observed in ovarian granulosa cells. Immunostaining for active caspase-3 and the TUNEL staining of apoptotic cells were also increased in ovaries exposed to COU in a dose-dependent manner. These results suggest new sights into the effect of lactational exposure to COU on the female reproductive health.

Clinical trial: the effect and timing of food on the pharmacokinetics and pharmacodynamics of dexlansoprazole MR, a novel Dual Delayed Release formulation of a proton pump inhibitor--evidence for dosing flexibility

BACKGROUND

Dexlansoprazole MR is a proton pump inhibitor with a Dual Delayed Release (DDR) formulation designed to prolong the dexlansoprazole plasma concentration-time profile. The presence of food or time of dosing relative to food may affect dexlansoprazole absorption.

AIMS

To evaluate the effect of food on the pharmacokinetics (PK) and pharmacodynamics (PD) of dexlansoprazole following oral administration of dexlansoprazole MR.

METHODS

In this open-label, single-dose, randomized, 4-way crossover study, 48 healthy subjects received placebo (day 1) and dexlansoprazole MR 90 mg (day 3) after fasting, 5 or 30 min before a high-fat breakfast, or 30 min after a high-fat breakfast. Intragastric pH (days 1 and 3) and PK (day 3) of dexlansoprazole were assessed over a 24-h interval after each dose.

RESULTS

Following administration of dexlansoprazole MR under fasted/fed conditions, mean dexlansoprazole plasma concentration-time profiles generally exhibited two distinct peaks, resulting from the DDR formulation. Increases in dexlansoprazole maximum plasma concentration (12-31%) and area under the plasma concentration-time curve (9-21%) were observed with the fed regimens; however, differences in intragastric pH were not considered clinically relevant.

CONCLUSION

Dexlansoprazole MR can be administered without regard to food or the timing of food in most patients.

Multigeneration reproductive and developmental toxicity study of bar gene inserted into genetically modified potato on rats

Each specific protein has an individual gene encoding it, and a foreign gene introduced to a plant can be used to synthesize a new protein. The identification of potential reproductive and developmental toxicity from novel proteins produced by genetically modified (GM) crops is a difficult task. A science-based risk assessment is needed in order to use GM crops as a conventional foodstuff. In this study, the specific characteristics of GM food and low-level chronic exposure were examined using a five-generation animal study. In each generation, rats were fed a solid pellet containing 5% GM potato and non-GM potato for 10 wk prior to mating in order to assess the potential reproductive and developmental toxic effects. In the multigeneration animal study, there were no GM potato-related changes in body weight, food consumption, reproductive performance, and organ weight. Polymerase chain reaction (PCR) was carried out using extracted genomic DNA to examine the possibility of gene persistence in the organ tissues after a long-term exposure to low levels of GM feed. In each generation, the gene responsible for bar was not found in any of the reproductive organs of the GM potato-treated male and female rats, and the litter-related indexes did not show any genetically modified organism (GMO)-related changes. The results suggest that genetically modified crops have no adverse effects on the multigeneration reproductive-developmental ability.

Assessment of estrogenic and androgenic activities of tetramethrin in vitro and in vivo assays

Tetramethrin, a synthetic pyrethroid insecticide, is used globally for agriculture, and thus potential environmental exposure to tetramethrin is a concern. Environmental chemicals that are hormonally active (particularly estrogen or androgen) may adversely affect the reproductive and endocrine systems. However, little is known about the estrogenic and androgenic activities of tetramethrin. In this study, uterine CaBP-9k gene expression assay and a uterotrophic assay were conducted for estrogenic activity assessment of tetramethrin, and a Hershberger assay was conducted for androgenic activity. Estrogen receptor (ERalpha and ERbeta) protein levels were also measured in tetramethrin-treated rat uteri. Northern blot analysis showed reduction in uterine CaBP-9k mRNA levels in response to tetramethrin, as well as when rats were given both tetramethrin and 17beta-estradiol (E2). In the uterotrophic assay using 18-d-old female Sprague-Dawley rats, subcutaneous treatment with tetramethrin (5 to 800 mg/kg/day) for 3 d led to a statistically significant decrease in absolute and relative uterine wet weights at all doses tested. Moreover, tetramethrin blocked the effect of E2 on uterine weights. In addition, tetramethrin reduced absolute and relative vaginal wet weights, and also inhibited the increases of vaginal weights produced by E2. Tetramethrin showed no androgenic on antiandrogenic activities in the Hershberger assay. These results suggest that tetramethrin might exert endocrine-disrupting effects on female rats through antiestrogenic action.

Neurotoxic effects of alcohol and acetaldehyde during embryonic development

Alcohol drinking during pregnancy results in abnormal fetal development, including fetal alcohol syndrome (FAS) in humans and experimental animals. FAS is characterized by two major effects, including central nervous system (CNS) dysfunction and multiple anomalies recognizable mainly as a typical face. However, the mechanisms of alcohol-induced embryotoxicity have not been clearly demonstrated. The aim of the present study was to investigate the possible mechanisms underlying ethanol-induced FAS in the developing embryo. First, ethanol-induced developmental abnormalities were investigated in vitro. Postimplantation embryos at gestation day (GD) 9.5 were cultured for 48 h and observed for morphological changes. Ethanol-mediated changes in proteins regulated apoptosis (p53 and bcl-2), antioxidant (vitamin E and catalase) activities, generation of reactive oxygen species (ROS), and oxidative DNA damage shown as 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured in embryonic midbrain cells. Alcohol or acetaldehyde significantly induced cytotoxicity in cultured rat embryonic midbrain cells. The levels of p53, bcl-2, and 8-OHdG were concomitantly changed by alcohol and acetaldehyde treatment in midbrain cells. Injured cells induced by ROS were increased by alcohol or acetaldehyde treatment in midbrain cells. Cotreatment with alcohol or acetaldehyde and catalase decreased cytotoxicity in midbrain cells. In postimplantation embryo culture, alcohol or acetaldehyde-treated embryos showed retardation of embryonic growth and development in a concentration-dependent manner. These results indicate that alcohol and its metabolite acetaldehyde induce fetal developmental abnormalities by disrupting cellular differentiation and growth. Data demonstrate that some antioxidants can partially protect against the alcohol-induced embryonic developmental toxicity.

Identification of Transcripts Involved in Resistance Responses to Leaf Spot Disease Caused by Cercosporidium personatum in Peanut (Arachis hypogaea)

ABSTRACT Late leaf spot disease caused by Cercosporidium personatum is one of the most destructive foliar diseases of peanut (Arachis hypogaea) worldwide. The objective of this research was to identify resistance genes in response to leaf spot disease using microarray and real-time polymerase chain reaction (PCR). To identify transcripts involved in disease resistance, we studied the gene expression profiles in two peanut genotypes, resistant or susceptible to leaf spot disease, using cDNA microarray containing 384 unigenes selected from two expressed sequenced tag (EST) cDNA libraries challenged by abiotic and biotic stresses. A total of 112 spots representing 56 genes in several functional categories were detected as up-regulated genes (log(2) ratio > 1). Seventeen of the top 20 genes, each matching gene with known function in GenBank, were selected for validation of their expression levels using real-time PCR. The two peanut genotypes were also used to study the functional analysis of these genes and the possible link of these genes to the disease resistance trait. Microarray technology and real-time PCR were used for comparison of gene expression. The selected genes identified by microarray analysis were validated by real-time PCR. These genes were more greatly expressed in the resistant genotype as a result of response to the challenge of C. personatum than in the susceptible genotype. Further investigations are needed to characterize each of these genes in disease resistance. Gene probes could then be developed for application in breeding programs for marker-assisted selection.

Differential gene profiles in developing embryo and fetus after in utero exposure to ethanol

Alcohol consumption during pregnancy results in morphological abnormalities in the fetuses of humans and experimental animals, and is referred to as fetal alcohol syndrome (FAS). However, the molecular mechanism underlying FAS has not been completely elucidated. The aim of the present study was to investigate the potential molecular mechanisms of ethanol-induced FAS in the developing embryo and fetus. cDNA microarray analysis was used to screen for altered gene profiles. Ethanol at a teratogenic dosage (3.8 g/kg, twice a day) was administered intraperitoneally to pregnant C57Bl/6J mice from gestation day (GD) 6 to 8. Morphologic observations showed excessive malformations of the craniofacial regions (reduction of the face, the absence of eyes, nose, jaw, and mandible, underdevelopment of vibrissae areas, cleft lip, and palate) in ethanol-exposed embryos (GD 10) and fetusus (GD 15). cDNA microarray analysis showed alterations in several gene profiles, including the "palate, lung, and nasal epithelium clone (plunc), "neurofilament, " and "pale ear. " Of these genes, the expressions of plunc were confirmed by reverse-transcription polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization. The plunc was highly expressed in the craniofacial region, specifically in upper airways and nasopharyngeal epithelium. RT-PCR analysis revealed that normal plunc mRNA expression levels were present in GD 15 fetuses, but not in GD 10 embryos. Interestingly, ethanol significantly downregulated the plunc expression in GD 15 fetuses. Our results suggest that ethanol-induced FAS is due in part to the downregulation of plunc expression in the fetus, and this gene may be a candidate biological marker for FAS.

Mechanism of antifertility in male rats treated with 3-monochloro-1,2-propanediol (3-MCPD)

3-Monochloro-1,2-propanediol (3-MCPD) is a food contaminant that is often found in foods containing acid-hydrolyzed (AH) protein, like seasonings and savory food products. The purpose of the present study was to investigate the effects of 3-MCPD on male fertility, sperm, and hormonal levels and its antifertility mechanism. In vivo male fertility testing was performed to observe the adverse effects of 3-MCPD on the functioning of the male reproductive system and pregnancy outcome. 3-MCPD (0.01-5 mg/kg) was administered daily by gavage to Sprague-Dawley (SD) male rats for 4 wk. At the end of the pretreatment period, male rats were mated overnight with untreated females. Males successfully inducing pregnancy were sacrificed to assess sperm parameters, reproductive organ histopathology, and spermatogenesis. The resulting pregnant females were sacrificed on 20 of gestation to evaluate pregnancy outcome. The paternal administration of 3-MCPD (5 mg/kg) was found to result in adverse effects on male fertility and pregnancy outcome without inducing remarkable histopathological changes in testes and epididymides. Additionally, 3-MCPD (5 mg/kg) significantly reduced sperm motility, copulation, fertility indices, and the number of live fetuses showed steep dose-response curves. 3-MCPD did not affect spermatogenesis or induce hormonal changes in the blood and testes of male rats. An in vitro hormone assay using primary isolated Leydig cells showed no significant changes in related hormone levels after 3-MCPD treatment. To evaluate the effects of 3-MCPD on apoptotic induction and H+-ATPase levels in the testis and epididymis, 10 or 100 mg/kg of 3-MCPD was administered by gavage to male rats and testes and epididymides were examined at 3, 6, 12, and 24 h later. Apoptosis was not detected in the testes of animals treated with 100 mg/kg 3-MCPD. However, the level of H+-ATPase in the cauda epididymis was reduced by 3-MCPD treatment. These results indicate that 3-MCPD induced a spermatotoxic effect, which was mediated by reduced H+-ATPase expression in the cauda epididymis, and suggest that an altered pH level in the cauda epididymis might lead to a disruption of sperm maturation and the acquisition of motility.

Neuronal differentiation of embryonic midbrain cells by upregulation of peroxisome proliferator-activated receptor-gamma via the JNK-dependent pathway

Our previous study showed that the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist 15-deoxy-PGJ(2) has the promoting ability to differentiate neuronal PC12 cells. To expand our study, the effect of 15-deoxy-PGJ(2) on the differentiation of embryonic midbrain cells into dopaminergic neuronal cells was investigated in this study. The relationship between cell differentiation with activation of PPAR-gamma and the possible signal pathway were also investigated. 15-Deoxy-PGJ(2) increased neurite extension, a typical characteristic of the differentiation of embryonic midbrain cells isolated from 12-day rat embryos in a dose-dependent manner. The expression of differentiation markers, neurofilament, tyrosine hydroxylase, and nestin, was also increased by the treatment of 15-deoxy-PGJ(2). Consistent with the increasing effect on cell differentiation, 15-deoxy-PGJ(2) increased the expression and transcriptional activity of PPAR-gamma in cultured embryonic midbrain cells. In addition, the expression of PPAR-gamma and NeuN in the differentiated neuron of fetus (17 days) and adult rat brain was co-localized. Furthermore, treatment of PPAR-gamma antagonist bisphenol A diglycidyl ether blocked 15-deoxy-PGJ(2)-induced neuronal differentiation of embryonic midbrain cells and expression of PPAR-gamma. To elucidate the possible signal pathway, the activation of mitogenic-activated protein (MAP) kinase family was determined. 15-Deoxy-PGJ(2) (0.5 microM) increased activation of Jun N-terminal kinase (JNK) and p38 kinase but not extra-signal response kinase (ERK). In addition, NGF (50 ng/ml) further increased the 15-deoxy-PGJ(2)-induced JNK activation. Moreover, pretreatment of specific inhibitor of JNK SP600125 blocked the 15-deoxy-PGJ(2)-induced JNK activation. This inhibition correlated well with the inhibition of neurite extension and expression of PPAR-gamma induced by 15-deoxy-PGJ(2). The present results therefore indicate that 15-deoxy-PGJ(2) stimulates differentiation of embryonic midbrain cells into dopaminergic neuronal cells, and its effect may be PPAR-gamma and JNK signal pathway dependent.

No androgenic/anti-androgenic effects of bisphenol-A in Hershberger assay using immature castrated rats

Several studies have demonstrated that bisphenol A (BPA) exhibited weak estrogenic activity in the 3-day uterotrophic assay using ovariectomized (OVX) and immature rats (Toxicol. Lett. 115 (2000) 231; Regul. Toxicol. Pharmacol. 32 (2000) 118; J. Toxicol. Sci. 26 (2001) 111) and BPA also possessed anti-androgenic activity in in vitro yeast based assays (J. Endocrinol. 158 (1998) 327). To investigate anti-androgenic effects of BPA. a rodent Hershberger assay was carried out using immature Sprague-Dawley male rats. An androgen agonist, testosterone (0.4 mg/kg per day), was administered for 7 consecutive days by subcutaneous (s.c.) injection as a positive control. Additionally, a pure androgen antagonist, flutamide (1, 5. 10 mg/kg per day. oral) was co-administered with testosterone (0.4 mg/kg per day s.c.). BPA was also administered orally with or without testosterone (0.4 mg/kg per day, s.c.) for 7 consecutive days. In the testosterone treated groups, glans penis, seminal vesicles, ventral prostate, and levator ani plus bulbocavernosus muscles (LABC) weights were significantly increased compared with control. However. flulamide dose-dependently inhibited the testosterone-induced re-growth of seminal vesicles, ventral prostate, and LABC, with a significant decrease at flutamide 1.0 mg/kg and above (P<0.05). Serum LH levels were also significantly increased (5 mg/kg and above, P<0.05), but no changes in serum testosterone levels. In contrast, BPA had no effects on the re-growth of seminal vesicles, ventral prostate and LABC induced by testosterone, and no significant differences were observed in serum LH and testosterone levels. In summary, the Hershberger assay could be a sensitive method for detecting androgenic or anti-androgenic chemicals, but BPA did not exhibit any androgenic or anti-androgenic activities in Hershberger assay.

Comparative evaluation of alkylphenolic compounds on estrogenic activity in vitro and in vivo

This study was undertaken to compare the sensitivity of screening test methods and to investigate the structure-activity relationships of the estrogenic activity of alkylphenolic compounds (APs) using in vitro and in vivo assays. Two in vitro systems, MCF-7 cell proliferation (E-screen assay) and competitive binding assay to estrogen receptor (ER), were selected to evaluate the estrogenic effects. Uterotrophic assay and Calbindin-D9K (CaBP9K) mRNA expression were also examined in ovariectomized Sprague-Dawley female rats. A series of APs with various alkyl groups were examined, namely, 4-propylphenol, 4-butylphenol, 4-t-butylphenol, 4-pentylphenol, 4-nonylphenol, 4-octylphenol, 4-t-octylphenol, and 4-phenylphenol, and 17beta-estradiol (E2) was used as a positive control. In the E-screen assay, E2 was found to induce maximum proliferation of MCF-7 cells at 1 nM. Among the APs, 4-t-octylphenol and 4-nonylphenol were found to be considerably more potent than any other compound and estrogenic effects were detectable at 1 and 10 microM, respectively. 4-t-Octylphenol and 4-nonylphenol inhibited the binding of E2 to the ER of MCF-7 cells in a competitive ER binding assay. The uterotrophic effects to APs (10, 50, 200, and 400 mg/kg/d) were compared to E2 (1 microg/kg) in ovariectomized rats after treatment for 3 d. 4-Nonylphenol, 4-t-octylphenol, and 4-phenylphenol produced dose-dependent increases in the uterine weights of ovariectomized rats. In the CaBP-9K mRNA expression test, CaBP-9K mRNA levels were detected in the uteri of ovariectomized rats treated with 4-pentylphenol (400 mg/kg), 4-nonylphenol, 4-phenylphenol (200 and 400 mg/kg), and 4-t-octylphenol (50 mg/kg and above), respectively. In the dot blot assay, CaBP-9K mRNA levels were significantly increased in rats exposed to 4-t-octylphenol (200 and 400 mg/kg), 4-pentylphenol, 4-nonylphenol, and 4-phenylphenol (400 mg/kg), respectively. Among the APs, compounds with bulky alkyl groups or higher carbon numbers possessed higher estrogenic capacity. In addition, the pattern of CaBP-9K expression correlated with that of the 3-d uterotrophic assay. Therefore, our results suggest that the CaBP-9K gene might be used as a potential biomarker for the screening of endocrine disruptors.

Inhibitory effect of peroxisome proliferator-activated receptor gamma agonist on ochratoxin A-induced cytotoxicity and activation of transcription factors in cultured rat embryonic midbrain cells

The effects of 15-deoxy-delta12,14-prostaglandin J2 (15-deoxy PGJ2) on ochratoxin A (OTA)-induced neurotoxicity and on the activation of transcription factors activator protein-1 (AP-1) and nuclear factor-kappa B (NF-kappaB) were investigated in cultured rat embryonic midbrain cells. Twelve-day rat embryo midbrain cells were cultured for 48 h. OTA (0.5 or 1 microg/ml) and/or 1.5-deoxy PGJ2 (0.5 microM) were then added for 48 h. Cell number and neurite outgrowth were determined to assess the neurotoxicity of OTA. AP-1 and NF-kappaB activation was determined by gel mobility shift assay after 3 h of exposure to OTA and/or 15-deoxy PGI2. OTA caused concentration-dependent reductions in neurite outgrowth and cell number, and induced AP-1 and NF-kappaB activation. Cotreatment with 15-deoxy PGJ2 (0..5 microM) blocked OTA-induced decrease in neurite outgrowth and cell number and inhibited AP-1 and NF-kappaB activation. 15-Deoxy PGJ2 (0.5 microM) caused the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in the cells. Results show that 1.5-deoxy PGJ2 blocked OTA-induced neurotoxicity by inhibiting AP-1 and NF-kappaB activation in cultured rat embryonic midbrain cells.

Mapping microbial biodiversity

We report the development of a prototype database that "maps" microbial diversity in the context of the geochemical and geological environment and geographic location. When it is fully implemented, scientists will be able to conduct database searches, construct maps containing the information of interest, download files, and enter data over the Internet.

Should all infertile males undergo urologic evaluation before assisted reproductive technologies? Two cases of testicular cancer presenting with infertility

OBJECTIVE

To report two cases of testicular cancer in patients presenting with infertility.

DESIGN

Case reports.

SETTING

University-affiliated urology practice.

PATIENT(S)

Two men presenting with infertility.

INTERVENTION(S)

Complete history and physical, hormonal assays, semen analysis, scrotal ultrasound, radical orchiectomy.

MAIN OUTCOME MEASURE(S)

Testicular pathology specimens.

RESULT(S)

Testicular cancer was diagnosed in two men sent to a urology clinic for infertility treatment.

CONCLUSION(S)

A thorough evaluation should be completed in all males in couples presenting with infertility.

Effects of ochratoxin A on cytotoxicity and cell differentiation in cultured rat embryonic cells

In the present study, the effects of ochratoxin A (OTA) on cytotoxicity, cell differentiation, and other cell functions in the embryonic midbrain cells, which are dopaminergic, were compared to those in the limb bud cells, which are nondopaminergic, to assess the selectivity of OTA central action. Twelve-day rat embryo midbrain and limb bud cells were cultured in Dulbecco's modified Eagle's medium nutrient and Ham's F12 (1:1) mix ture containing 10% Nuserum for 96 h in the presence of various concentrations of OTA. OTA signicfiantly reduced the levels of protein, DNA and glutathione, and [H]thymidine incorporation into DNA in both embryonic midbrain and limb bud cells in a similar concentration-dependent manner. The IC50 values for cytotoxicity measured by neutral red uptake were 1.10 microM in the midbrain cells and 1.05 microM in the limb bud cells. The IC50 values of cell differentiation were 1.10 microM in the midbrain cells and 1.0 microM in the limb bud cells. The addition of exogenous glutathione (32.5 microM) did not change the OTA-induced fall in protein and DNA levels, or the IC50 values of cytotoxicity and differentiation in the midbrain and limb bud cells. Data show that OTA does not appear to exert a selective toxic dopaminergic cell action and that OTA-induced cytotoxicity and inhibition of cell differentiation were not prevented by exogenous glutathione.

In vitro metabolism of the HIV-1 protease inhibitor ABT-378: species comparison and metabolite identification

HIV protease inhibitor ABT-378 (ABT-378) was metabolized very extensively and rapidly by liver microsomes from mouse, rat, dog, monkey, and humans. The rates of NADPH-dependent metabolism of ABT-378 ranged from 2.39 to 9.80 nmol.mg microsomal protein-1.min-1, with monkey liver microsomes exhibiting the highest rates of metabolism. ABT-378 was metabolized to 12 metabolites (M-1 to M-12), which were characterized by mass and NMR spectroscopy. The metabolite profile of ABT-378 in liver microsomes from all five species was similar, except that the mouse liver microsomes did not form M-9, a minor secondary metabolite. The predominant site of metabolism was the cyclic urea moiety of ABT-378. In all five species, the major metabolites were M-1 (4-oxo-ABT-378) and M-3 and M-4 (4-hydroxy-ABT-378). Metabolite M-2 (6-hydroxy-ABT-378) was formed by rodents at a faster rate than by dog, monkey, and human liver microsomes. Metabolites M-5 to M-8 were identified as monohydroxylated derivatives of ABT-378. Metabolites M-9 and M-10 were identified as hydroxylated products of M-1. Metabolites M-11 and M-12 were identified as dihydroxylated derivatives of ABT-378. The metabolite profile in human hepatocytes and liver slices was similar to that of human liver microsomes. The results of the current study indicate that ABT-378 is highly susceptible to oxidative metabolism in vitro, and possibly in vivo, in humans.

Effects of severe hypoxemia on mesenteric blood flow in neonatal piglets

BACKGROUND

The purpose of this work was to determine the effects of hypoxemia on systemic hemodynamic variables and regional conduit arterial blood flows in neonatal piglets.

MATERIALS AND METHODS

Using transit time blood flow probes, cardiac output and cranial mesenteric artery blood flow were monitored in groups of prematurely delivered (90% of term gestational age) and 2-week-old piglets prior to, during, and after exposure to a 30-min hypoxic (FIO2 = 0.12) challenge.

RESULTS

The documented alterations in systemic mean arterial pressure and cardiac output pressure during hypoxia and reoxygenation were consistent with the maturational age of the animals. In response to hypoxia, all animals demonstrated significant reductions in mesenteric blood flow, with returns to baseline levels during the 30-min reoxygenation phase. In still other prematurely delivered piglets, nutrient mesenteric arterial blood flows were measured using in vivo videomicroscopy. The marked hypoxemia-induced decline in mucosal blood flow was reversed by reoxygenation.

CONCLUSIONS

The physiologic mechanisms responsible for neonatal mesenteric vasoactive responsiveness are present in conduit and in nutrient vessels well prior to birth and can be activated by a significant perturbation. These observations are germane insofar as they provide a stable, age-matched acute animal model to study neonatal intestinal ischemic diseases, including necrotizing enterocolitis.

Neither dopamine nor dobutamine corrects mesenteric blood flow depression caused by positive end-expiratory pressure in a rat model of acute lung injury

OBJECTIVE

To determine if either dopamine or dobutamine would counteract the deleterious effect that positive end-expiratory pressure (PEEP) has on cardiac output and mesenteric blood flow in a rat model of acute lung injury.

DESIGN

Prospective, randomized, controlled trial in a clinically relevant model of acute lung injury.

SETTING

Microcirculation research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

The animals were anesthetized with pentobarbital (30 mg/kg) by intraperitoneal injection. They underwent tracheostomy, jugular and femoral vein cannulation, femoral artery cannulation, carotid artery thermistor placement, and bowel preparation for in vivo video microscopy. Acute lung injury was created by administering 0.1 N hydrochloric acid (1 mL/kg) via the tracheostomy. Dopamine or dobutamine (2.5 or 12.5 microg/kg/min), followed by two intravenous fluid boluses, was administered to rats ventilated with 5, 10, 15, and 20 cm H2O of PEEP.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, thermodilution cardiac output, mesenteric arteriolar diameter, and red blood cell velocity were measured and mesenteric blood flow was calculated. Cardiac output was depressed in rats exposed to 20 cm H2O of PEEP by 32+/-2%. The corresponding values for cardiac output depression at 20 cm H2O of PEEP in rats receiving 2.5 and 12.5 microg/kg/min of dopamine and 2.5 and 12.5 microg/kg/min of dobutamine were 31+/-1%, 21+/-1%, 29+/-0%, and 24+/-2%, respectively. Mesenteric blood flow was depressed in rats ventilated with 20 cm H2O of PEEP by 74+/-3%, while the corresponding values in rats exposed to 20 cm H2O of PEEP and receiving 2.5 or 12.5 microg/kg/min of dopamine or 2.5 or 12.5 microg/kg/min of dobutamine were 86+/-3%, 77+/-3%, 73+/-3%, and 66+/-3%, respectively. Fluid boluses did not correct the deficits in cardiac output or mesenteric blood flow caused by the combination of acute lung injury and PEEP.

CONCLUSIONS

The higher doses of dopamine and dobutamine partially, but insignificantly, corrected the cardiac output depression caused by PEEP in a model of acute lung injury. Neither dose of dopamine nor dobutamine was able to improve PEEP-induced mesenteric blood flow depression.

Polypharmacy: a case report and new protocol for management

BACKGROUND

Polypharmacy is an important issue in primary care, yet few data are available concerning its prevalence, complications, and management in clinical medicine. The following case illustrates the clinical perils of polypharmacy and serves as a point for critical discussion.

METHODS

MEDLINE was searched, using the key word "polypharmacy," from 1994 to the present. A case report of polypharmacy is described, and a novel protocol for the management of polypharmacy is proposed.

RESULTS

Polypharmacy can lead to unnecessary expense, wasted time, and embarrassment on the part of the patient and confusion and mismanagement on the part of the physician. The literature reveals controversy surrounding the definition of polypharmacy and reflects the considerable morbidity and expense associated with polypharmacy. Finally, the SAIL protocol shows that physicians need to keep in mind simplicity, adverse effects, indications, and a precise list of all medications to manage appropriately a patient's drug regimen.

CONCLUSIONS

Polypharmacy is associated with morbidity and iatrogenic complications. The SAIL protocol can be a useful tool in the management of this entity. More research needs to be done on the prevalence, complications, and management of polypharmacy.

Vitamin A, visual pigments, and visual receptors in Drosophila

The fly visual system has served for decades as a model for receptor spectral multiplicity and vitamin A utilization. A diverse armamentarium of structural techniques has dovetailed with convenient electrophysiology, photochemistry, genetics, and molecular biology in Drosophila to facilitate recent progress, which is reviewed here. New data are also presented. Ultrastructure of retinula cells of carotenoid-deprived flies shows that organelles associated with protein biosynthesis, i.e., rough endoplasmic reticulum and Golgi apparatus, are present, while organelles associated with rhabdomere turnover, i.e., multivesicular bodies (MVBs), are rare. Ultrastructure and morphometry suggest that retinoic acid-rearing stimulates membrane export and rhabdomere buildup, even though functional rhodopsin is missing. Confocal microscopy suggests that RH4, one of the ultraviolet rhodopsins, may reside in the previously-described pale fluorescent R7 cells with RH3 in the yellow fluorescent R7 cells.

Hepatic uptake of choline in rat liver basolateral and canalicular membrane vesicle preparations

Choline, an endogenous quaternary ammonium ion, is transported into the liver by both saturable and nonsaturable processes. The objective of the present investigation was to determine the driving force(s) for uptake of choline in rat liver basolateral membrane (blLPM) and canalicular membrane (cLPM) vesicles. Choline is transported into an osmotically sensitive intravesicular space in both blLPM and cLPM. Uptake of [3H]choline into both blLPM and cLPM exhibited temperature dependence (0 degree C vs. 37 degrees C). A valinomycin-induced inside-negative K+ diffusion potential significantly stimulated initial uptake of [3H]choline in both vesicles. Choline uptake in blLPM and cLPM was not stimulated in the presence of an inwardly directed sodium gradient or an outwardly directed H+ gradient, and ATP did not enhance choline uptake in cLPM. Choline itself and structurally similar derivatives, such as hemicholinium-3 and succinylcholine, inhibited [3H]choline uptake 11 to 92% (at 10-fold higher concentrations) in blLPM and cLPM. Other cations, including N1-methylnicotinamide, thiamine and d-tubocurarine, and cardioglycosides did not inhibit choline transport in either vesicle preparation. In addition, [3H]choline uptake into both blLPM and cLPM was enhanced when vesicles were preloaded with nonradiolabeled choline (trans-stimulation). Kinetic studies indicated that choline was transported into blLPM by both saturable and passive processes and into cLPM predominantly by a saturable process. These results suggest that the transport of choline is likely mediated by a potential-sensitive conductive pathway in both blLPM and cLPM. The electrogenic pathway in cLPM may play a role in the reabsorption of choline from bile.

Control of Drosophila opsin gene expression by carotenoids and retinoic acid: northern and western analyses

In the fly, thorough retinoid deprivation is possible, to optimize investigation of the effects of vitamin A metabolites and retinoic acid (RA) on visual development. Retinoids had been found to control fly opsin gene transcription, though this finding was contested. Northern blots on Drosophila heads showed that mRNA of Rh1 (the predominant rhodopsin) was high in vitamin A replete controls, very low in deprived flies, and increased upon feeding carrot juice to deprived flies as early as 1 hr. Expression of the ribosomal protein 49 [rp49] gene (the control) was equal both in deprivation and in replacement. Recovery of Rh1 protein upon such carotenoid replacement followed, barely detectable on Western blots at 4 hr but conspicuous by 8 hr. Alternative chromophore deprivation with yeast-glucose food yielded flies with opsin mRNA on Northerns but not rhodopsin, as demonstrated by Western blots, spectrophotometry and the electroretinogram (ERG). Rh1's mRNA but not Rh1 protein resulted from rearing flies from egg to adult on the otherwise deprivational medium supplemented with RA or beef brain-heart infusion. By comparing results from these different media it was concluded that: [1] deprivation and replacement affect opsin gene transcription; and [2] contradictory conclusions were from chromophore deprivation which does not eliminate all retinoid dependent factors which could affect the opsin promoter. Preliminary evidence shows that carotenoid deprivation decreases two proteins relevant to visual function: [1] phospholipase C (PLC); and [2] Drosophila retinoid binding protein (DRBP).

Visualization of iontophoretic transport paths in cultured and animal skin models

Physiological structures associated with iontophoretic paths in hairless mouse skin and two cultured skin models ("EpiDerm" by Mattek, Corp., and "SKIN2" by Advanced Tissue Sciences, Inc.) are reported. Visualization of ionic paths at current densities between 20 and 100 microA/ cm2 is accomplished by the counterdirectional transport of Fe(CN)6(4-) and Fe3+, resulting in the controlled precipitation of colloidal Prussian blue, Fe4[Fe(CN)6]3, at sites of high ionic conductivity. Examination of the Fe4[Fe(CN)6]3-stained tissues using optical microscopy allows unequivocal assignment of iontophoretic paths to physiological structures in the stratum corneum. Deposition of Fe4[Fe(CN)6]3 occurs exclusively at hair follicles in hairless mouse skin, indicating that these appendages provide highly conductive porous paths during iontophoresis. In contrast, the counterdirectional transport of Fe(CN)6(4-) and Fe3+ across cultured skin models, which lack appendages, results in the deposition of Fe4-[Fe(CN)6]3 along the boundaries of corneocytes. This observation suggests that paracellular iontophoretic transport through lipid bilayer regions is the predominant transport path in the absence of low-resistance pores.

Comparison of eight microcomputer dietary analysis programs with the USDA Nutrient Data Base for Standard Reference

OBJECTIVE

To compare the general operating features and nutrient databases of eight microcomputer dietary analysis programs.

DESIGN

A 3-day food record with 73 food items was entered into each program by the authors. The general operating features of the program were summarized and evaluated. The nutrient database was evaluated by comparing the nutrient analysis output with the 1993 US Department of Agriculture (USDA) Nutrient Data Base for Standard Reference (NDB), full version, release 10, for microcomputers.

RESULTS

The programs varied in cost, number of foods and nutrients in the database, use of non-USDA data, and inputting of data for missing values. We also found differences in the quality of user manuals and help screens, ease of food entry and averaging of 3-day nutrient intake, speed of analyzing and printing results, quality and number of print/export options, and overall ease of learning and using the program. All but one of the programs were within 15% of the USDA NDB for energy, protein, total fat, and total carbohydrates. However, there was some difference in the number of other nutrients and food components varying more than 15% from the USDA NDB. These differences occurred because of variations in the number of food items included in each programs' database and the number of missing nutrient values in the database.

APPLICATIONS

Our results demonstrate the importance of carefully choosing a microcomputer dietary analysis program that is suitable to the user's specific and predetermined needs.

In vitro metabolism of terfenadine by a purified recombinant fusion protein containing cytochrome P4503A4 and NADPH-P450 reductase. Comparison to human liver microsomes and precision-cut liver tissue slices

The metabolism of terfenadine was studied with a cDNA-expressed/purified recombinant fusion protein containing human liver microsomal cytochrome P4503A4 (CYP3A4) linked to rat NADPH-P450 reductase (rF450[mHum3A4/mRatOR]L1) and was compared with that observed in the presence of human liver microsomes and precision-cut human liver tissue slices. In all three cases, [3H]terfenadine was metabolized to at least three major metabolites. LC/MS (electrospray) analysis confirmed that these metabolites were alpha, alpha-diphenyl-4-piperidinomethanol (M5), t-butyl hydroxy terfenadine (M4), and t-butyl carboxy terfenadine (M3), although the level of M5 detected in the presence of fusion protein was greater than that found with microsomes or tissue slices. Two additional metabolites, M1 (microsomes and tissue slices) and M2 (fusion protein), were also detected, but remain uncharacterized. Consumption of parent drug (microsomes: KM = 9.58 +/- 2.79 microM, Vmax = 801 +/- 78.3 pmol/min/nmol CYP; fusion protein: KM = 14.1 +/- 1.13 microM, Vmax = 1670 +/- 170 pmol/min/nmol CYP) and t-butyl hydroxylation to M4 (microsomes: KM = 12.9 +/-3.74 microM, Vmax = 643 +/- 62.5 pmol/min/nmol CYP, ; fusion protein: KM = 30.0 +/- 2.55 microM, Vmax = 1050 +/- 141 pmol/min/nmol CYP) obeyed Michaelis-Menten kinetics over the terfenadine concentration range of 1-200 microM. Ketoconazole, a well-documented CYP3A inhibitor, effectively inhibited terfenadine metabolism in all three models. The conversion of M4 to M3, studied with human liver microsomes and fusion protein, was NADPH-dependent and inhibited by ketoconazole. It is concluded that cDNA-expressed CYP3A4, in the form of a NADPH-P450 reductase-linked fusion protein, may also serve as a model for studying the metabolism of terfenadine in vitro and many other drugs.

Disaggregation in population forecasting: do we need it? And how to do it simply

"We have described a method for reducing the dimensionality of the forecasting problem by parsimoniously modeling the evolution over time of the age schedules of vital rates. This method steers a middle course between forecasting aggregates and forecasting individual age specific rates: we reduce the problem to forecasting a single parameter for fertility and another one for mortality. We have described a number of refinements and extensions of those basic methods, which preserve their underlying structure and simplicity. In particular, we show how one can fit the model more simply, incorporate lower bounds to the forecasts of rates, disaggregate by sex or race, and prepare integrated forecasts of rates for a collection of regions. We also discuss alternate approaches to forecasting the estimated indices of fertility and mortality, including state-space methods. These many versions of the basic method have yielded remarkably similar results." (SUMMARY IN FRE)

Stochastic population forecasts for the United States: beyond high, medium, and low

"This article presents and implements a new method for making stochastic population forecasts that provide consistent probability intervals. We blend mathematical demography and statistical time series methods to estimate stochastic models of fertility and mortality based on U.S. data back to 1900 and then use the theory of random-matrix products to forecast various demographic measures and their associated probability intervals to the year 2065. Our expected total population sizes agree quite closely with the Census medium projections, and our 95 percent probability intervals are close to the Census high and low scenarios. But Census intervals in 2065 for ages 65+ are nearly three times as broad as ours, and for 85+ are nearly twice as broad. In contrast, our intervals for the total dependency and youth dependency ratios are more than twice as broad as theirs, and our ratio for the elderly dependency ratio is 12 times as great as theirs. These items have major implications for policy, and these contrasting indications of uncertainty clearly show the limitations of the conventional scenario-based methods."

[Modeling and projecting mortality in Chile]

"In a recent paper, Lee and Carter developed a new method for analyzing and forecasting time series of age specific mortality, and applied it to the U.S. population. In this paper, we extend that method to deal with various problems of incomplete data common in Third World populations, and then apply the method to forecast mortality in Chile." (SUMMARY IN ENG)

Fertility decline in Prussia: estimating influences on supply, demand, and degree of control

Change in marital fertility in 407 Prussian Kreise from 1875 to 1910 is modeled to depend on the gap between the number of desired surviving births, N*, divided by child survival, s, and the number that would be born under natural marital fertility, M, given the age at marriage. Some fraction of this gap is averted, depending on the propensity to avert unwanted births, D. Although none of these components is observed directly, we can estimate each indirectly under strong assumptions. Decline in N*/s accounts for twice as much of the decline in fertility as does an increase in D. Natural fertility rose during the period. Unwanted births increased slightly, despite a tripling of births averted. The most important causes of decline in N* were increases in female labor supply, real income, and health workers. A rising level of education is the most important cause of increasing propensity to avert births. Demand-side changes were important causes of the transition, but changes in readiness to contracept also were important, as was the interaction of the two.

Famine, revolt, and the dynastic cycle: population dynamics in historic China

"Historians have long noticed that population declines in ancient China often coincided with dynasty changes, and that most of these declines were the result of internecine wars which, in turn, were often initiated by famine or density pressure. Since the interactions between density pressure, internecine wars, and dynasty changes cannot be explained by the traditional age-specific density-dependent population structure, we propose to use a bandit/peasant/ruler occupation-specific population model to interpret the dynamic socio-economic transitions of ancient Chinese population, and provide econometric support to our model. We also highlight the rich dynamics of the composition of human population, a factor which was often neglected in previous research on general populations."

Visual laser ablation of the prostate: clinical experience in 108 patients

Visual laser ablation of the prostate was performed on 108 patients (ages 44 to 84 years) as an outpatient procedure from May 1992 to October 1992. Preoperatively, the patients underwent digital rectal examinations, determination of prostate specific antigen levels and transrectal ultrasound guided biopsies when necessary to rule out the presence of prostate cancer. The Urolase laser fiber delivery system was used to transmit laser energy from a neodymium: YAG generator. For the 97 patients with preoperative and postoperative American Urological Association symptom index testing, scores decreased by an average of 12.59 (p < 0.001). For the 75 patients with preoperative and postoperative uroflow rates an average increase of 4.92 ml. per second (p < 0.001) was noted following the procedure. Only 3 patients required hospitalization for an average of 1.33 days. No patient required a blood transfusion. There have been no fluid or electrolyte abnormalities following visual laser ablation of the prostate. There have been no recognizable urethral strictures, deaths or postoperative sepsis. Only 3 patients experienced retrograde ejaculation. We found visual laser ablation of the prostate to be a cost-effective and less morbid alternative to traditional transurethral resection of the prostate.

Modeling and forecasting U.S. sex differentials in mortality

"This paper examines differentials in observed and forecasted sex-specific life expectancies and longevity in the United States from 1900 to 2065. Mortality models are developed and used to generate long-run forecasts, with confidence intervals that extend recent work by Lee and Carter (1992). These results are compared for forecast accuracy with univariate naive forecasts of life expectancies and those prepared by the Actuary of the Social Security Administration."

Stochastic demographic forecasting

"This paper describes a particular approach to stochastic population forecasting, which is implemented for the U.S.A. through 2065. Statistical time series methods are combined with demographic models to produce plausible long run forecasts of vital rates, with probability distributions. The resulting mortality forecasts imply gains in future life expectancy that are roughly twice as large as those forecast by the Office of the Social Security Actuary.... Resulting stochastic forecasts of the elderly population, elderly dependency ratios, and payroll tax rates for health, education and pensions are presented."

Comparison of six microcomputer dietary analysis systems with the USDA Nutrient Data Base for Standard Reference

We compared the general operating features and nutrient databases of six microcomputer dietary analysis systems. A 3-day food record with 73 food items was entered into each program; nutrient averages were compared with the US Department of Agriculture Nutrient Data Base for Standard Reference (USDA NDB), full version, release 9, for microcomputers. The six programs were found to vary widely in cost, number of foods and nutrients in the database, use of non-USDA data and imputation of data for missing values, number of print/export options, time to analyze the 3-day food record, and overall ease of use. Although all of the microcomputer dietary analysis systems were within 7% of the USDA NDB for energy, protein, total fat, and total carbohydrates, the proportion of other nutrients varying more than 15% from the USDA NDB varied considerably between programs. Variance among programs for 3-day food record nutrient values occurred because of differences in the number of food items included in the database (leading to varying degrees of substitution), the recency of the nutrient data (whether or not the most recent USDA releases had been incorporated), and the number of missing values (the degree to which non-USDA sources or estimated calculations were used to fill in the blanks from the USDA standard). Our results demonstrate that it is important for each dietitian to carefully choose a microcomputer dietary analysis system that is suitable to specific and predetermined needs.

Submucosal ureteral calculi: a new entity?

We describe 3 patients with ureteral calculi who failed multiple extracorporeal shock wave lithotripsy treatments and whose stones could not be visualized by ureteroscopy despite radiological confirmation. We contend that these ureteral stones migrated submucosally and are refractory to the aforementioned treatment modalities. Each patient had a common presenting complaint of intermittent flank pain 5 years in duration, leading us to believe that long-standing stone impaction is a prerequisite for this entity. Our experience is reviewed.

Stereoselective synthesis of the diunsaturated metabolites of valproic acid

Two diene metabolites of valproic acid (VPA), (E)-2-n-propyl-2,4-pentadienoic acid and (E)-2-(1'-propenyl)-(E)-2-pentenoic acid, were stereoselectively synthesized. Mesylate elimination in the final step to produce the unsaturation at position 2 was stereospecific for the (E)-configuration in the case of 2. Gas chromatography-mass spectroscopy and NMR were used to confirm the configuration of each diene including the minor isomers, (Z)-2-n-propyl-2,4-pentadienoic acid and (Z)-2-(1'-propenyl)-(E)-2-pentenoic acid. Analysis of the dienes, as PFB derivatives by negative chemical ionization GC-MS from a serum extract of a patient on VPA therapy, revealed the presence of four peaks that in order of elution correspond to 9, 18, 1, and 2.

U.S. births and limit cycle models

Lee's (1974) formal demographic feedback models summarize the implications for births and age-structure of neo-Malthusian theories of baby booms such as those of Easterlin. For some parameter values, such models imply sustained cycles, so-called "limit cycles", in births. Frauenthal and Swick recently reestimated a continuous-age version of Lee's basic cohort model with U.S. series and, contrary to Lee's original findings, concluded that "limit cycles oscillations have been occurring in U.S. births." This article disputes their conclusion, ascribing it to an inconsistency in detrending procedures. Furthermore, it corrects Lee's original conclusion by showing that his alternative period labor-force feedback model, estimated from U.S. series, leads to cycles of implausibly long period. This article thus reopens the question of whether any feedback model could account for the observed cycles in U.S. births.

Induced population growth and induced technological progress: their interaction in the accelerating stage

"A simple model of Malthusian population growth combined with population-induced technological progress generates accelerating growth. The model may be relevant for a first stage of growth in which natural resource limitations can be overcome through technological progress; it is not applicable to a later stage in which resource constraints are more resistant. Parameter values are roughly inferred from historical experience." (SUMMARY IN FRE)

Population dynamics of humans and other animals

Human population dynamics, at least until the past century, have probably been governed by homeostasis and in this resembled those of other animals. Because human population homeostasis was probably substantially weaker than among large mammals, its operation has been less obvious. Nonetheless, the empirical evidence for advanced agriculturalists is compelling. Unlike animals, the human population has tended toward equilibria that have been tending upward at an accelerating rate. The acceleration might reflect long-run positive feedback between density and technological progress, as Boserup has suggested. Because homeostasis was weak, its role in shorter run historical explantation is limited; its force was gentle and easily overwhelmed by other particular influences. Malthusian oscillation, in the sense of distinctive medium-run dynamics arising from homeostasis, probably did not occur. And because homeostasis was weak, density dependence can in principle explain only a minute proportion of the annual variation in population growth rates. Yet homeostasis plays an essential role in demographic theory. Without it, we are incapable of explaining population size and change over time except by recounting a mindless chronology of events back to the beginning of humanity--whenever that was. Without it, we cannot explain the response of population growth to economic growth. Without it, we cannot explain recovery from catastrophe or the rapid natural increase in many frontier regions. Without it, we cannot properly analyze the influence of climatic variation and other partially density-independent factors. Our basic understanding of human history requires a grasp of what homeostasis can explain and what it cannot. A homeostatic approach to population dynamics also leads to questions about the roles of reproductive norms and institutions, not just whether they encourage high or low fertility, but whether they make natural increase responsive to resource abundance. And if they do, whether they strike the balance of population and the means of subsistence at a relatively prosperous or impoverished level. Such considerations may contribute to an understanding of broad preindustrial differences among the regions of the world in densities, average levels of vital rates, and living standards--which was very much how Malthus viewed the matter. Ordinary homeostatic tendencies essentially vanish in the course of economic development, and they were probably all but gone from much of Europe by the end of the 19th century.(ABSTRACT TRUNCATED AT 400 WORDS)

Scrotal fat necrosis

A case of scrotal fat necrosis is presented. The clinical presentation usually is characteristic and the condition can be managed nonoperatively.