Ventrally emigrating neural tube cells migrate into the developing vestibulocochlear nerve and otic vesicle

Virtually all cell types in the inner ear develop from the cells of the otic vesicle. The otic vesicle is formed by the invagination of non-neural ectodermal cells known as the otic placode. We investigated whether a recently described cell population, originating from the ventral part of the hindbrain neural tube known as the ventrally emigrating neural tube (VENT) cells, also contributes cells to the otic vesicle. The ventral hindbrain neural tube cells were labeled with the fluorescent vital dye DiI or replication-deficient retroviruses containing the LacZ gene in chick embryos on embryonic day 2, after the emigration of neural crest from this region. One day later, the labeled cells were detected only in the hindbrain neural tube. Shortly thereafter, the labeled cells began to appear in the eighth (vestibulocochlear) cranial nerve and otic vesicle. From embryonic day 3.5-5, the labeled cells were detected in the major derivatives of the otic vesicle, i.e. the endolymphatic duct, semicircular canals, utricle, saccule, cochlea, and vestibulocochlear ganglion. That the emigrated cells originated from the ventral part of the hindbrain neural tube was confirmed by focal application of DiI impregnated filter paper and with quail chimeras. It is concluded that, in addition to the otic placode cells, the otic vesicle also contains the ventrally emigrating neural tube cells, and that both cell populations contribute to the structures and cell types in the inner ear. It is well known that inductive signals from the hindbrain are required for the morphogenesis of the inner ear. The migration of the hindbrain neural tube cells into the otic vesicle raises the possibility that the inductive effect of the hindbrain might be mediated, at least in part, by the ventrally emigrating neural tube cells and that, therefore, a mechanism exists that involves cells rather than diffusible molecules only.

Ventrally emigrating neural tube cells contribute to the normal development of heart and great vessels

We investigated the contributions of a recently described population of neural tube cells, which participates in the development of a variety of tissues, to the development of the heart and great vessels. These cells, termed as the ventrally emigrating neural tube (VENT) cells, originate in the ventral part of the hindbrain neural tube, emigrate at the site of attachment of the cranial nerves, and populate their respective target tissues. VENT cells of the caudal hindbrain neural tube at the level of the vagus nerve, which were previously reported to migrate into the heart, were tagged with replication-deficient retroviruses containing the LacZ gene in chick embryos, after the emigration of neural crest from this region. In older embryos, VENT cells were detected in a variety of locations including the ventricles, atria, their septa, aorticopulmonary septum, and great vessels of the heart. Immunostaining with a specific marker revealed that VENT cells differentiated into smooth muscle cells of great vessels. Differentiation of VENT cells into cardiac muscle cells was reported previously. Extirpation of the VENT cells prior to their departure from the neural tube resulted in some common cardiovascular malformations: thin-walled ventricles and atria, ventricular and atrial septal defects, persistent truncus arteriosus, and stenosis of the great vessels. These results suggest that a novel population of neural tube cells also contributes to the normal development of the heart and great vessels. Thus, the heart and great vessels develop from three sources of cells: mesoderm, neural crest, and VENT cells.

A second source of precursor cells for the developing enteric nervous system and interstitial cells of Cajal

The enteric nervous system is believed to be derived solely from the neural crest cells. This is partly based on the belief that the neural crest cells are the sole neural tube-derived cells colonizing the gastrointestinal tract. However, recent studies have shown that after the emigration of neural crest cells an additional population of cells emigrate from the cranial neural tube. These cells originate in the ventral part of the hindbrain, emigrate through the site of attachment of the cranial nerves, and colonize a variety of developing structures including the gastrointestinal tract. This cell population has been named the ventrally emigrating neural tube (VENT) cells. We followed the fate of these cells in the gastrointestinal tract. Ventral hindbrain neural tube cells of chick embryos were tagged with replication-deficient retroviral vectors containing the LacZ gene, after the emigration of neural crest from this region. In control embryos, the viral concentrate was dropped on the dorsal part of the neural tube. Embryos were sacrificed from embryonic days 3-12 and processed for the detection of LacZ positive ventrally emigrating neural tube cells. These cells colonized only the foregut, specifically the duodenum and stomach. Immunostaining with the neural crest cell marker HNK-1 showed that they were HNK-1 negative, indicating that they were not derived from neural crest. Cells were detected in three locations: (1). the myenteric and submucosal plexus of the enteric nervous system; (2). circular smooth muscle cell layer; and (3). mucosal lining of the lumen. A variety of specific markers were used to identify their fate. Some ventrally emigrating neural tube cells differentiated into neurons and glial cells, indicating that the enteric nervous system in the foregut develops from an additional source of precursor cells. It was also found that some of these cells differentiated into interstitial cells of Cajal, which mediate impulses between the enteric nervous system and smooth muscle cells, whereas others differentiated into epithelium. Altogether, these results indicate that the ventrally emigrating neural tube cells are multipotential. More importantly, they reveal a novel source of precursor cells for the neurons and glial cells of the enteric nervous system. The developmental and functional significance of the heterogeneous origin of the cell types remains to be established.

The posterior cruciate ligament: an anthropometric study in Asians and evaluation of safe limits for bony tunnel creation during reconstruction

INTRODUCTION

Quantitative data regarding the dimensions of the posterior cruciate ligament (PCL) and its insertions have not been studied in Asians, and concerns have been raised regarding the danger of vascular injury when the bony tunnels are created during arthroscopically-assisted reconstruction.

MATERIALS AND METHODS

Ten male cadavers were used in this study, incorporating dissection and procedural arms. In the procedural arm, the path of the drill bit was tracked fluoroscopically as the tibial and femoral tunnels were created during simulated reconstructive surgery, and the effect of varying knee flexion angles was studied. Fluoroscopic images were analysed using specialised image processing software.

RESULTS

The mean length of the PCL at full extension was 37.7 +/- 1.9 mm, and the mean mid-substance width was 13.7 +/- 1.7 mm. The mean sagittal distance between the exit point of the tibial tunnel and the anterior surface of the popliteal artery, across all knee flexion positions, was merely 6.0 mm (range, 2.8 to 10.2 mm). This distance tended to increase with increasing knee flexion, but this was not statistically significant. The mean distance between the exit point of the femoral tunnel and the femoral artery was 51.1 mm (range, 42.1 to 59.0 mm).

CONCLUSIONS

The dimensions of the PCL and its insertions in Asians do not vary greatly from those reported for Western subjects. The distance from the exit point of the tibial tunnel to the popliteal artery is very small and, although this distance increases with increasing knee flexion, the improvement in the safety margin may neither be clinically nor statistically significant. The margin of safety for drilling of the femoral tunnel is much greater.

Protective effect of acorus calamus against acrylamide induced neurotoxicity

Exposure of rats to acrylamide (ACR) caused hind limb paralysis in 58% of the animals on day 10 and decreased behavioural parameters, namely distance travelled, ambulatory time, stereotypic time and basal stereotypic movements compared with the control group. These rats also had a decrease in the reduced glutathione (GSH) content and glutathione-S-transferase (GST) activity in the corpus striatum and an increase in striatal dopamine receptors, as evident by an increase in the binding of 3H-spiperone to striatal membranes. Treatment with the ethanol:water (1:1) extract of the rhizomes of Acorus calamus (AC-002) increased the GSH content and GST activity in the corpus striatum while insignificant changes were observed in other parameters. Rats treated with ACR and AC-002 in combination had a lower incidence of paralysis (18%) compared with those treated with ACR alone on day 10 of the experiment. The rats also showed a partial recovery in other behavioural parameters. The levels of GSH content and GST activity increased in the corpus striatum, while the dopamine receptors decreased compared with the ACR treated rats. The results suggest that the neurobehavioural changes produced by ACR may be prevented following treatment with Acorus calamus rhizomes.

Stimulation electromyography as a method of intraoperative identification of the recurrent laryngeal nerve in thyroid surgery

INTRODUCTION

The iatrogenic injury of the recurrent laryngeal nerve during thyroid surgery still represents a major problem because of the great physiologic and psychologic trauma to the patients. The incidence of this complication ranges between 1% and 15% depending on the thyroid pathology and type of surgery.

AIM

To evaluate the potential of stimulation electromyography as a method of intraoperative prophylaxis of iatrogenic injuries of the recurrent laryngeal nerve.

MATERIAL AND METHODS

Intraoperative monitoring of the recurrent laryngeal nerve based on stimulation electromyography, which was introduced in the Clinics of Surgery and Otorhinolaryngology at the Higher Medical Institute in Plovdiv, was applied in thyroid surgery using Neurosign 100 (Magstim Company Ltd., Wales, UK) apparatus. The study involved 5 experimental dogs and 73 recurrent laryngeal nerves in 47 patients treated in the clinics from November 1, 1999 to February 15, 2000.

RESULTS

In all experimental animals and patients the electrical stimulation was successful triggering an "M" response of the laryngeal muscles (the vocal muscle). A stable contact was achieved between the recording (needle) electrodes and the vocal folds. None of the patients had signs of laryngeal palsy or complaints other from the usual in endotracheal intubation.

CONCLUSION

The results suggest that the intraoperative stimulation electromyography of the recurrent laryngeal nerve is a safe and effective method for evaluation of the nerve integrity during and at the end of the operation.

Neuropsychological studies on lead battery workers

This study assessed the psychological status of 60 lead-acid battery workers occupationally exposed to low level lead and 30 referents in Lucknow. Digit spans and symbol, Bourdon-wiersma vigilance and Raven's Progressive matrices tests were administered. Significant impairments in concentration, attention, auditory and visual memory, psycho-motor speed, perceptual accuracy, and visual reasoning were observed in the workers compared to the referents. The deficits were not related to exposure duration since the magnitude of the impairments observed in workers with 1-y duration was the same as in those with more (up to 30 years) work duration. The blood lead of the battery workers was significantly elevated. There were functional deficits of the central nervous system in the lead-acid battery workers.

Competing approaches to analysis of failure times with competing risks

For the analysis of time to event data in contraceptive studies when individuals are subject to competing causes for discontinuation, some authors have recently advocated the use of the cumulative incidence rate as a more appropriate measure to summarize data than the complement of the Kaplan-Meier estimate of discontinuation. The former method estimates the rate of discontinuation in the presence of competing causes, while the latter is a hypothetical rate that would be observed if discontinuations for the other reasons could not occur. The difference between the two methods of analysis is the continuous time equivalent of a debate that took place in the contraceptive literature in the 1960s, when several authors advocated the use of net (adjusted or single decrement life table rates) rates in preference to crude rates (multiple decrement life table rates). A small simulation study illustrates the interpretation of the two types of estimate - the complement of the Kaplan-Meier estimate corresponds to a hypothetical rate where discontinuations for other reasons did not occur, while the cumulative incidence gives systematically lower estimates. The Kaplan-Meier estimates are more appropriate when estimating the effectiveness of a contraceptive method, but the cumulative incidence estimates are more appropriate when making programmatic decisions regarding contraceptive methods. Other areas of application, such as cancer studies, may prefer to use the cumulative incidence estimates, but their use should be determined according to the application.

Analysis of failure time hierarchical data in the presence of competing risks with application to oral contraceptive pill use in Egypt

Problems of practical interest in the analysis of data on contraceptive use, from Demographic and Health Surveys (DHS), include the estimation of the cause-specific probability of discontinuation by time t (the cumulative incidence function), in the presence of other competing causes and the evaluation of the effect of covariates on the cause-specific hazards of discontinuation. Methods of analysis of failure time data with competing risks are by now fairly well developed in the case of a simple random sample. However, the data from the DHS are clustered by geographical areas and include multiple episodes per woman. For a marginal (population average) approach, we propose using methods developed for simple random samples with standard errors calculated using a double bootstrap to take account of the clustered hierarchical nature of the data. In the conditional approach, the cause-specific hazards are modelled as log-linear functions of the covariates conditional on random effects of clusters and women, using a three-level multinomial discrete-time logit model. The methods are applied to data from Egypt 1992 DHS on the oral contraceptive pill use.

The link between postnatal abstinence and extramarital sex in Côte d'Ivoire

Whether the link, found in Benin, between postnatal abstinence and husbands' extramarital contacts can be generalized to other West African countries is assessed in this study. Data from the 1994 Demographic and Health Survey, Côte d'Ivoire, obtained from monogamous husbands concerning their extramarital sexual behavior in the two months preceding the survey were linked to data reported by wives concerning postnatal abstinence over the same time period. Logistic regression was applied to assess the link between these two factors, net of the effects of possible confounders. A significant effect of postnatal abstinence on the probability that the husband reported at least one extramarital partner was found. Unprotected extramarital sex was two times more common among men who observed conjugal abstinence than it was among other men. Other predictors of extramarital sex were urban-rural residence, region, education, and whether or not husband and wife had the same religious affiliation. Because condom use is low in this population, the protective effect of marital abstinence is offset by an increased probability that husbands will seek extramarital partners during the postpartum period. The results confirm the earlier findings for Benin and can likely be generalized to most of West Africa.

Quality of care and contraceptive pill discontinuation in rural Egypt

Indicators of family planning service access and quality were generated using the Egypt DHS-I (1988) and the Egypt Service Availability Survey (1989), and linked to episodes of contraceptive pill use. Multilevel analysis was used to ascertain whether or not these access and quality indicators influence the continuation of pill use, net of women's socioeconomic, demographic and motivational characteristics. A model with random components at the cluster and women levels was fitted for all reasons of discontinuation, except desire for pregnancy, at 24 months of use. Net of women's background characteristics, the results show that facilities with smaller numbers of health personnel trained in family planning, a lack of access to facilities with female doctors and a lack of range of available methods are associated with a high risk of discontinuation of pill use for all reasons except desire for pregnancy.

Vestibular schwannomas: clinical presentation, management and outcome

OBJECTIVE

To review the demographic trends clinical spectrum, diagnosis, management and out come of patients with vestibular Schwannoma and to identify areas where improvements are needed.

METHODS

All patients with vestibular schwannoma admitted to the Aga Khan University Hospital over the past 11 years were reviewed retrospectively.

RESULTS

The age range of majority of 22 patients analyzed, was 41-50 years (23%). Hearing loss was the most common presenting symptom (96%). Other clinical features included cranial nerve palsies (59%) and headache (55%). Fifty percent had signs of raised intracranial pressure. Neuroimaging revealed "Stage IV b" (tumor distorting the brainstem and compressing the 4th ventricle) in 50% cases. Neurosurgical intervention was carried out in 86%; mainly using the retrosigmoid approach. Postoperative complications included facial nerve palsy in 13 (65%) and hydrocephalus in 5 (25%) patients. Hearing determined clinically was preserved in three patients (14%). One patient died during the inpatient stay.

CONCLUSION

Presentation of these patients is late and the outcome is poor.

Immunohistochemical nuclear staining for P53 in nodular scabies

Fifty patients with scabies were included in this study. Clinical, parasitological and histopathological study of all patients was done. P-53 expression was examined, using immunohistochemical techniques. Biopsies of nodular scabies showed atypical changes in the epidermis, the dermis showed dense inflammatory infiltrate. Focal positivity for P-53 have been demonstrated which could favour premalignant changes, and recommend further investigations.

Effect of arteriovenous fistula for hemodialysis on limb circulation

The number of patients with end-stage renal disease maintained on chronic hemodialysis is increasing progressively. Arteriovenous fistula (AVF) is a common vascular access for hemodialysis, however, its effect on limb distal circulation has not been studied well. Palpation of pulse at the wrist is a crude method of clinical assessment. Over one year period, 26 AVFs were created; 16 at the wrist (61.5%) and ten fistulas at the elbow (38.5%). Six of the latter were through the brachio-basilic approach while the other four were performed by basilic vein transposition. Doppler measurement of both wrist-brachial index (WBI) and finger pressure was carried out for all patients pre-operatively and on the first post-operative day. Of the patients with AVF created at the elbow, there was a decrease of WBI in seven patients (70%) and a decrease of finger pressure in three (30%); one patient (14%) had steal syndrome. Creation of AVF at the wrist resulted in a decrease of WBI in one patient (6.25%) and a decrease of finger pressure in another patient (6.25%). WBI changes as a result of creation of AVF at the elbow were significantly greater than the changes of those fistulas performed at the wrist (P < 0.001). On the other hand, the difference between the effect of both procedures on finger pressure was statistically not significant. These results may help to explain the higher incidence of steal syndrome in patients with elbow fistulas compared to patients with wrist fistulas. Further studies on a larger scale are required to determine the value of non-invasive indices at which AVF creation would have future risk of compromised distal limb circulation.

Sanctions and childhood mortality in Iraq

BACKGROUND

In 1999 UNICEF, in cooperation with the government of Iraq and the local authorities in the "autonomous" (northern Kurdish) region, conducted two similar surveys to provide regionally representative and reliable estimates of child mortality (the subject of this paper) and maternal mortality.

METHODS

In a cross-sectional household survey in the south/centre of Iraq in February and March, 1999, 23105 ever-married women aged 15-49 years living in sampled households were interviewed by trained interviewers with a structured questionnaire that was developed using the Demographic and Health Surveys questionnaire and following a pre-test. In a similar survey in the autonomous region in April and May 14 035 ever-married women age 15-49 were interviewed.

FINDINGS

In the south/centre, infant and under-5 mortality increased during the 10 years before the survey, which roughly corresponds to the period following the Gulf conflict and the start of the United Nations sanctions. Infant mortality rose from 47 per 1000 live births during 1984-89 to 108 per 1000 in 1994-99, and under-5 mortality rose from 56 to 131 per 1000 live births. In the autonomous region during the same period, infant mortality declined from 64 to 59 per 1000 and under-5 mortality fell from 80 to 72 per 1000. Childhood mortality was higher among children born in rural areas, children born to women with no education, and in boys, and these differentials were broadly similar in the two regions.

INTERPRETATION

Childhood mortality clearly increased after the Gulf conflict and under UN sanctions in the south/centre of Iraq, but in the autonomous region since the start of the Oil-for-Food Programme childhood mortality has begun to decline. Better food and resource allocation to the autonomous region contributed to the continued gains in lower mortality, whereas the situation in the south/centre deteriorated despite the high level of literacy in that region.

Locomotor and learning deficits in adult rats exposed to monosodium-L-glutamate during early life

Neonatal administration of neurotoxic doses of monosodium-L-glutamate (MSG) to rats causes neuronal necrosis of the hypothalamus along with behavioral abnormalities. In the present study the behavioral effects in rats treated with subneurotoxic doses of MSG (2 mg/g, p.o., for 10 days) at the weaned stage were investigated at day 90 post-dosing. The MSG-treated rats did not show significant changes in any of the components of spontaneous locomotor activity but, after apomorphine challenge, marked decreases in the distance travelled, ambulatory and stereotypic times, and the number of stereotypic movements with an increase in the resting time were observed. Significant decrease in the active avoidance learning performance was observed in the MSG-treated rats in the learning (acquisition) phase without any changes in the extinction and relearning phases. The results indicate that exposure to MSG in early life in rats could lead to subtle behavioral aberrations in late adulthood.

Complications of carbon monoxide poisoning

OBJECTIVE

Acute carbon monoxide poisoning is a common problem that occurs during winter and leads to serious complications.

METHODS

We retrospectively studied 24 consecutive cases admitted with the aim of finding the causes and outcome of acute carbon monoxide poisoning.

RESULTS

The source of poisoning was charcoal in 71% of patients, motor gasoline in 21%, and other causes in 8%. Immediate complications included altered consciousness level in 54% of patients, metabolic acidosis in 46%, pneumonia in 42%, cardiac arrhythmia in 29% and rhabdomyolysis in 25%. Late neurological complications occurred in 17% of patients. All the patients received 100% oxygen. Eleven patients (46%) required mechanical ventilation. Ultimately, 19 patients (79%) recovered completely, 4 (17%) had neurological or cardiac disorders, and 1 (4%) died.

CONCLUSION

Immediate and late complications are common in carbon monoxide poisoning cases admitted to the hospital especially when they arrive late. Time lapse between exposure and presentation may have a role in predicting the outcome.

Effects of AQ4N and its reduction product on radiation-mediated DNA strand breakage

Supercoiled plasmid pBR322 DNA was irradiated in phosphate buffer by 60Co gamma-rays at a dose rate 19.26 Gy/min and total dose of 10 Gy in the presence of a bioreductive antitumour prodrug namely 1,4-bis [¿2-(dimethylamino-N-oxide)ethyl¿ amino] 5, 8-dihydroxyanthracene-9,10-dione (AQ4N) and its DNA affinic reduction product 1,4-bis[¿2(dimethylamino)ethyl¿ amino] 5,8-dihydroxyanthracene-9,10-dione (AQ4) under air and nitrogen. AQ4N and AQ4 were found to protect against radiation-induced plasmid single and double strand breakage as assessed by agarose gel electrophoresis. The differences between the two agents, and between atmospheres of air or nitrogen were negligible. It was also found that the protection efficiencies of the compounds were pH dependent and showed maximum protection at pH 6. These results indicate that protection of DNA by AQ4 and AQ4N against radiation damage is an indirect effect since both agents are equally effective despite major differences in their DNA affinity. It is likely that radiation-induced phosphate buffer radicals are intercepted by AQ4 and AQ4N in a pH-dependent process.

Ventrally emigrating neural tube cells differentiate into vascular smooth muscle cells

A multipotential cell population originating in the ventral part of the hindbrain neural tube, the ventrally emigrating neural tube cells (VENT cells), has recently been shown to migrate into the craniofacial mesenchyme. Because vascular smooth muscle cells develop from this mesenchyme, we sought to determine if the VENT cells contributed to their differentiation. VENT cells were tagged with replication-deficient retroviral vector with LacZ by microinjection into the lumen of the rostral hindbrain of chick embryos on day 2. Embryos were processed for the detection of LacZ positive cells on day 7. LacZ-positive cells were present in the wall of craniofacial arteries and veins. Immunostaining with the smooth muscle alpha-actin confirmed the labeled cells to be smooth muscle cells. It is concluded that some vascular smooth muscle cells differentiate from neural tube cells. the developmental and functional significance of which remains to be established.

Ventrally emigrating neural tube cells contribute to the formation of Meckel's and quadrate cartilage

A population of multipotential neuroepithelial cells originating in the ventral portion of the hindbrain neural tube has been shown recently to emigrate at the site of attachment of the trigeminal nerve. These ventrally emigrating neural tube cells populate the mesenchyme of the first pharyngeal (branchial) arch. Because the Meckel's and the quadrate cartilage develop from this mesenchyme, we sought to determine whether these ventrally emigrating neural tube cells contributed to their development. The ventral neural tube cells were tagged with a replication-deficient retroviral vector containing the LacZ gene. This method permanently labels the descendents of the neural tube cells; thus, they can be subsequently tracked during development. The viral concentrate was microinjected into the lumen of the rostral hindbrain of chick embryos, after the emigration of neural crest is finished, on embryonic day 2 (stage 14). In control embryos, the virus was placed on top of the neural tube. Embryos were killed on days 3, 4, and 7 and processed for the detection of LacZ-positive cells. By day 7, the Meckel's and the quadrate cartilage can be easily recognized. LacZ-positive cells were seen in both cartilages. They were located in perichondrium and in the cartilage. Immunostaining with the neural crest cell marker HNK-1 indicated that the LacZ-positive cells were HNK-1 negative. The HNK-1-positive neural crest-derived cells were located in the cartilage but not in the perichondrium. These results indicate that the chondrocytes in the Meckel's and the quadrate cartilage differentiate from two sources of cells; the ventrally emigrating neural tube cells and the neural crest. The developmental significance of differentiation of cartilage from the ventral neural tube cells and of the heterogeneous origin of chondrocytes in morphogenesis remains to be established. Dev Dyn 1999;216:37-44.

Effect of malathion, an organophosphorus pesticide, on the serum proteins of Heteropneustes fossilis (BLOCH)

The use of pesticides to control pests and to increase food production is a normal process in this modern age. The objective of this study was to determine changes in different serum protein fractions caused by the action of malathion, a commonly used pesticide. We used Indian catfish, Heteropneustes fossilis. The fish were exposed to a sublethal dose of 4 mg/L of malathion for 24, 48, 72, and 96 hr. The LC50 value at 96 hr was found to be 11.676 mg/L. The results showed the formation of three low and four high mobility fractions and the disappearance of some protein fractions at different periods of exposure. The appearance of fractions A, B, and C (low-mobility proteins) may be due to altered immune responses caused by cellular damage. The appearance of new high-mobility fractions (D, E, F, and G) is possibly due to the breakdown of red blood cells and other cellular components. The findings of this study indicate that the high concentration of malathion (4 mg/L) induced more alterations in serum proteins compared with the low concentration (1.2 mg/L) used in our previous study.

Mortality due to schistosomiasis mansoni: a field study in Sudan

Although schistosomiasis affects 200 million persons, 20 million of whom have advanced disease, little is known about the mortality pattern in areas of endemic schistosomiasis mansoni. In an attempt to assess the mortality rates in an endemic area in Sudan, we conducted two demographic surveys in a village in the Gezira area. Clinical, sonographic, and parasitologic examinations were performed in a randomly selected sample of 25% of the population in 1987 and 1994. One of us asked each head of household about the names, sex, and age of family members. Particularly, we asked about death in the family if any, history of schistosomiasis, abdominal swelling, and hematemesis. Possible causes of death were ascertained by reviewing medical records in the village dispensary and the district hospital. There were 42 deaths in the village. Four males died of hematemesis secondary to portal fibrosis. The crude mortality rate of schistosomiasis was is 51/100,000/year. The overall schistosomiasis fatality rate per year was 1/1,000 infected persons, but was as high as 11/100/infected patients with bleeding varices. These findings showed the impact of schistosomiasis on public health in this economically important region of Sudan.

Ventrally emigrating neural tube cells differentiate into heart muscle

A population of ventrally emigrating neural tube cells has been shown to migrate along the vagus nerve and contribute to the development of the gastrointestinal tract. Since the vagus also goes to the heart, we sought to determine if these cells migrated into the heart. Neural tube cells were tagged with replication-deficient retroviral vectors containing the LacZ gene, to permanently label their progeny. The virus was microinjected into the lumen of the caudal hindbrain of chick embryos on day 2. Embryos were later processed for the detection of LacZ positive cells. Labeled cells were initially confined to the neural tube. Later, they migrated in association with the vagus nerve into the heart, where they were located in the myocardium. Labeled cells were identified as cardiac muscle cells of non-neural crest origin, with specific markers. It is concluded that some cardiac muscle cells differentiate from the neural tube cells.

Post-partum sexual abstinence in West Africa: implications for AIDS-control and family planning programmes

OBJECTIVE

To assess whether the custom of prolonged post-partum sexual abstinence in Benin is associated with an increased incidence of extra-marital sexual contacts by husbands.

DESIGN

Cross-sectional survey of adult men and women.

METHODS

Data obtained from men on their extra-marital sexual behaviour in the past 12 months were linked to data on post-partum abstinence over the same time interval reported by wives. Multivariate analysis was applied to assess the association between conjugal abstinence and husband's extra-marital sex, net of the effects of possible confounders.

RESULTS

Approximately half of married men experienced post-partum abstinence in the past 12 months. In this group, 32% reported one or more extra-marital sexual contacts compared with 20% among those who experienced no abstinence (OR = 1.8, P < 0.001). This association is essentially unchanged after controlling for marriage type, age, education, urban-rural residence, income and household wealth. Age, income and wealth are also significant predictors of the probability of extra-marital sex. The effects of income and wealth largely disappear when attention is restricted to extra-marital sex without using a condom on the most recent occasion.

CONCLUSIONS

The potentially protective effect of prolonged abstinence after childbirth in Benin (and probably in much of West Africa) is offset by an increased probability that husbands will seek extra-marital partners without using condoms. Although not quantifiable, the enhanced longer-term risks of sexually transmitted diseases/HIV infection for wives probably outweigh the short-term benefits. Family planning practitioners in this region should not hesitate to recommended the early resumption of sex and suitable methods of post-partum contraception for women who express concern or uncertainty about their husband's behaviour.