Sheep from low-methane-yield selection lines created on alfalfa pellets also have lower methane yield under pastoral farming conditions

Selection lines of sheep with low and high CH yield (g/kg DMI; CH/DMI) are being developed on the basis of feeding pelleted alfalfa hay at 2.0 times maintenance ME requirements in respiration chambers, but their divergence under predominant grazing conditions, as in New Zealand, is not known. The objectives of this study were to determine CH emissions and rumen fermentation characteristics in sheep from low and high CH/DMI selection lines while grazing pasture. Two grazing experiments were conducted with 42 selection line ewes in March 2013 (Exp. 1) and 98 selection line progeny ewe hoggets in October/November 2014 (Exp. 2), with CH emissions estimated by the SF tracer technique and DMI estimated by titanium oxide in combination with natural long-chain -alkanes. Total daily CH production (g/d) was similar between high and low CH/DMI selection line sheep in Exp. 1 and lower for low CH/DMI progeny compared with high CH/DMI progeny in Exp. 2 ( < 0.05). The CH/DMI tended to be 20% lower for low CH/DMI line sheep compared with high CH/DMI selection line sheep in Exp. 1 ( < 0.10) and was 15% lower for the low CH/DMI line in Exp. 2 ( < 0.01). Total VFA concentration and concentrations (m) of acetate, butyrate, and isobutyrate plus isovalerate were lower ( < 0.05) for low CH/DMI line sheep compared with high CH/DMI selection line sheep in both experiments. The current study indicates that differences in CH/DMI and VFA concentrations in selection line sheep, previously established on alfalfa pellets, are also present to a similar magnitude when grazing pasture.

Cardiac magnetic resonance imaging in patients with systemic lupus erythematosus

Objectives:

To delineate the cardiac magnetic resonance (MR) appearances of cardiovascular disease (CVD) in patients with systemic lupus erythematosus (SLE), in comparison with transthoracic echocardiographs.

Methods:

Cardiac MR was performed on 22 patients with SLE—11 with previous CVD and 11 matched controls—using late gadolinium contrast enhancement (LGE) to identify areas of myocardial scarring; Transthoracic echocardiography (TTE) was performed on the same day.

Results:

Twenty female and two male patients participated. LGE was seen in 5/11 subjects in the CVD group (4/5 with previous myocardial infarction) and 1/11 in the control group. TTE detected myocardial abnormalities in 2/6 patients with LGE.

Conclusion:

The cardiac MR appearance of CVD in these patients with SLE was suggestive of coronary disease, rather than cumulative inflammatory muscle damage. Cardiac MR detected more abnormalities than TTE. Further studies of cardiac MR in patients with SLE are warranted to investigate these preliminary findings.

Triggering of acute coronary syndromes by physical exertion and anger: clinical and sociodemographic characteristics

OBJECTIVE

To investigate the role of vigorous physical exertion and anger as triggers of acute coronary syndromes (ACS) and to identify the clinical and sociodemographic correlates of triggering.

DESIGN

Prospective observational clinical cohort study.

SETTING

Four coronary care units in the London area.

PATIENTS

295 men and women with electrocardiographically and biochemically verified ACS.

MAIN OUTCOME MEASURES

Physical exertion in the 1 h and anger in the 2 h before symptom onset were assessed with structured interviews. Control periods were the equivalent hours one day earlier and usual rates over the past six months. Data were analysed by case-crossover methods.

RESULTS

Physical exertion was reported by 10% and anger by 17.4% of patients in the hazard period. The risk of ACS onset after physical exertion compared with light or no activity was 3.50 (95% confidence interval (CI) 1.37 to 10.6). The risk of onset with anger was 2.06 (95% CI 1.12 to 3.92). Physical exertion during the hazard period was related to an absence of premonitory symptoms, presentation with an ST elevation myocardial infarction (STEMI), low socioeconomic deprivation and higher future cardiovascular risk. Anger during the hazard period was more common in younger, socioeconomically deprived patients who presented with a STEMI.

CONCLUSIONS

Triggers are relevant across the spectrum of ACS. The distinct clinical and sociodemographic factors associated with physical exertion and anger suggest that different pathophysiological processes may be involved.

Inhibition of in-stent restenosis in rabbit iliac arteries with photodynamic therapy

OBJECTIVES

Photodynamic therapy (PDT, the combination of light with a photosensitising drug in the presence of oxygen) inhibits restenosis after angioplasty without stenting. This study assesses the potential of PDT for prevention of in-stent re-stenosis.

DESIGN AND METHODS

Normal rabbits were given the photosensitising agent 5-aminolaevulinic acid (ALA) 60 mg/kg, 3 h prior to endovascular illumination of the iliac artery (635 nm at 50 J/cm(2)) either immediately before or after deployment of an oversized (3 mm diameter) stent. PDT treated arteries were retrieved 3 or 28 days later and assessed for cell counts and vascular morphometry. Control arteries (stent but no PDT) were examined at 28 days.

RESULTS

There were no adverse events and all vessels were patent at the end of the study. At 3 days there was almost complete medial cell ablation when light was delivered before stent deployment (17+/-1 cells/hpf), with little effect when illumination followed stent deployment (184+/-17 cells/hpf, p<0.0001). Twenty-eight days after PDT, the neointimal areas were 1.41+/-0.52 mm(2) (stent with no PDT), 1.24+/-0.54 mm(2) (light after stent) and 0.60+/-0.21 mm(2) (light before stent) (p=0.004).

CONCLUSIONS

PDT before stent deployment caused almost complete medial cell ablation at 3 days with inhibition of in-stent restenosis at 28 days. PDT is worthy of further study as an adjuvant to percutaneous intervention in patients with vascular disease.

Epistaxis in children with vascular malformations--commentary of two cases and literature review

Vascular anomalies can cause epistaxis in children. The authors present two cases of recurrent epistaxis secondary to rare causes and discuss their presentations. Both cases were managed conservatively since intervention in these vascular lesions carries a high risk of damaging adjacent structures.

An unusual presentation of cat-scratch disease

Cat-scratch disease (CSD) is a relatively common entity, particularly in children. The most common sites of involvement are the axillary lymph nodes, followed by cervical, pre-auricular and submandibular lymph nodes. We present a case of cat-scratch disease in which the initial clinical features were indistinguishable from those of acute bacterial tonsillitis with jugulodigastric lymphadenopathy. This previously unreported apparent mode of presentation is discussed with reference to the current understanding of the disease.

Outcomes of submandibular duct re-implantation for sialorrhoea

Drooling is an important factor affecting the quality of lives of neurologically impaired children, and surgery often has to be performed. Submandibular duct relocation is a relatively simple procedure with a low complication rate, and has been carried out on 37 patients at the Sheffield Children's Hospital between 1986 and 1998. To determine the short-term and long-term outcome of this procedure, a questionnaire was sent to the parents/wards of the patients. Feedback was also obtained on complications, parents'/carers' perceptions and main concerns about the operation, particularly in those cases which did not improve. Both short-term (82.4%) and long-term (76.5%) control rates were high, and there were few complications, none of which had any long-term adverse effects. The most significant area of parental/carer dissatisfaction and concern in 'failed' cases was 'pain', and it was felt that proper preoperative counselling about analgesia and chances of failure is very important. We conclude that this is a safe, highly successful procedure which significantly improves the quality of lives of the majority of drooling children.

Effect of conductive hearing loss on the vestibulo-collic reflex

The vestibulo-collic reflex represents a promising test for evaluating the integrity of otolith function. We have investigated the threshold of this response in a group of normal subjects, and the effect of a conductive hearing loss. A positive response was recorded in 31 of 32 normal subjects. The threshold of the vestibulo-collic reflex varied from 80 to 97 dBHL in these subjects with a 95% response rate at a threshold at 96 dBHL. A total of 23 ears with a conductive hearing loss in 17 patients were also investigated. The average conductive hearing loss (at 0.5, 1, 2 and 4 kHz) ranged from 8.75 to 40 dBHL (average 24.46 dBHL). A positive response was recorded in only two ears. Therefore, the vestibulo-collic reflex has a high stimulus threshold which is dependant on reliable transmission of the click stimulus to the inner ear thus limiting is clinical use.

Autoradiographic localisation of [3H]-SCH23390 and [3H]-spiperone binding sites in honey bee brain

In the brain of the honey bee, dopamine receptors have been identified by using the vertebrate D1 dopamine antagonist [3H]-SCH23390 and the vertebrate D2 dopamine antagonist [3H]-spiperone. This study uses light microscope autoradiography to investigate the anatomical distributions of the binding sites labelled by [3H]-SCH23390 and [3H]-spiperone in tissue sections cut at three depths from the anterior surface of the brain. The binding of these radioligands differed significantly, in both density and distribution. Specific binding of [3H]-SCH23390, defined by using 5 x 10(-6) M cis-(Z)-flupentixol, was densest in regions of somata, such as the deutocerebral somatal rind, the somatal layer beneath the calyces of the mushroom bodies and the ventral protocerebral somatal group. High levels of [3H]-SCH23390 binding were also measured in the lateral protocerebrum. [3H]-Spiperone binding site density estimates were consistently lower than those of [3H]-SCH23390. Specific binding of [3H]-spiperone, determined by subtracting binding in the presence of 10(-4) M domperidone from the total binding, was highest in the alpha lobes, beta lobes, and calyces of the mushroom body neuropil. Relatively high binding was also measured in the central body and lateral protocerebral neuropil. These results suggest that the distribution of dopamine receptors in the brain of the bee is subtype specific, and they support the view that dopamine plays many roles in the insect central nervous system.

Gene delivery to the heart in vivo and to cardiac myocytes and vascular smooth muscle cells in vitro using herpes virus vectors

Herpes simplex virus 1 (HSV1), while usually thought of as neurotrophic, can also efficiently infect a wide variety of non-neuronal cell types and so might be developed as a vector for gene delivery to non-neuronal as well as neuronal cells. Here we have tested three different disabled HSV vectors for their ability to deliver a lacZ gene to primary cardiac myocytes and vascular smooth muscle cells in vitro, and used the most efficient virus to transfect the rat heart in vivo. We also assessed the degree of cytopathic effect of the various viruses on the cardiac myocytes in vitro by testing the effects on the frequency of beating in synchronously beating myocyte cultures. While an HSV mutant in which the essential immediate-early gene IE2 had been deleted gave high efficiency gene transfer to the cardiac myocytes in vitro and the rat heart in vivo, viruses in which ICP34.5 or ICP34.5 and VMW65 were inactive (and which were also unable to replicate in these cells) gave a much lower efficiency of gene transfer, mirroring the degree of cytopathic effect observed in the beating myocyte cultures. Gene transfer to the vascular smooth muscle cells was considerably less efficient than to the myocytes in all cases. These results indicate that while HSV may be inappropriate for highly efficient gene transfer to the arterial wall, efficient gene transfer can be achieved in the myocardium, and thus that HSV vectors may be suitable for the alteration of cardiac cell physiology in vivo.

Inhibition of intimal hyperplasia in balloon injured arteries with adjunctive phthalocyanine sensitised photodynamic therapy

OBJECTIVES

We investigated the effects of Photodynamic therapy (PDT) using Aluminium disulphonated phthalocyanine (AlS2Pc) on experimental intimal hyperplasia (FCIH).

MATERIALS AND METHODS

(a) Pharmacokinetics: Normal rats were injected with Als2Pc and carotid artery fluorescence was measured. (b) Normal artery PDT: Sensitised rats underwent carotid artery laser irradiation (50J/cm2, 675nm) and were assessed after 3 and 14 days and 1-6 months. (c) PDT: Rats underwent standard carotid artery balloon injury immediately prior to PDT and arteries were assessed at 2 to 26 weeks, together with laser, AlS2Pc, and untreated controls.

CHIEF OUTCOME MEASURES

(a) Fluorescence intensity in different arterial layers. (b) Medial smooth muscle cell counts per high power field (light microscopic). (c) Percentage amount of FCIH (area of intimal hyperplasia) as a ratio of the IEL (area enclosed by the internal elastic lamina).

RESULTS

(a) AlS2Pc fluorescence intensity increased with increasing dosage, with maximal fluorescence in the arterial media at 30 min. (b) PDT produced medial cell depletion at 3 days and persisted over 6 months without loss of vessel integrity. (c) PDT completely inhibited FCIH at 2 and 4 weeks. This was partial at 6 to 26 weeks (51% of untreated level). PDT inhibition of FCIH was significantly greater than in any of the control groups. p < 0.0001. Mann-Whitney Test.

CONCLUSION

Adjunctive AlS2Pc sensitised photodynamic therapy inhibits experimental intimal hyperplasia, by causing medial smooth muscle cell depletion. This offers a new approach to the management of angioplasty restenosis in patients.

Orbital and skin metastases in a polymorphous low grade adenocarcinoma of the salivary gland

We report the previously undocumented development of an orbital metastasis and skin metastases in a patient with polymorphous low grade adenocarcinoma (PLGA) 15 years after initial presentation. The clinical course, treatment and changing histological features are discussed.

Reproducibility of angiotensin converting enzyme inhibitor induced cough: a double-blind randomised study

1. The reproducibility of angiotensin converting enzyme inhibitor induced cough was examined in a double-blind cross over study in patients previously shown to have exhibited this side effect. 2. Ninety-seven patients who had experienced angiotensin converting enzyme inhibitor cough within the last 2 years were challenged with enalapril 20 mg daily for 4 weeks to establish eligibility. Eighty-eight of 97 (91%) patients experienced a repeat of their cough symptoms. Sixty-four patients entered the double-blind part of the study where they were treated with enalapril 20 mg and a renin inhibitor for up to 4 weeks in random order. These periods were separated by a minimum 4 week placebo wash out. 3. Of 59 evaluable patients who received enalapril a second time, 37 (62.7%) experienced cough again. Of 62 patients on the renin inhibitor 16 (25.8%) experienced cough, however as it was not equi-efficacious to enalapril no valid comparison could be made. 4. Angiotensin converting enzyme inhibitor cough is not reproducible within patients, as other factors are involved in the aetiology. Objective testing with blinded assessment together with symptom reporting, would give a more accurate measure of the incidence, and mechanism of this side effect.

Photodynamic therapy of normal and balloon-injured rat carotid arteries using 5-amino-levulinic acid

BACKGROUND

Although the management of atherosclerotic disease by the use of balloon angioplasty is widespread, the treatment is limited by restenosis in 30% to 50% of cases. Fibrocellular intimal hyperplasia, the main cause of restenosis, arises from proliferation and migration of medial smooth muscle cells (SMC) into the intimal layer. Factors leading to intimal hyperplasia are incompletely understood, and drugs have universally failed to influence clinical restenosis. Photodynamic therapy (PDT), the light activation of photosensitizing drugs to generate cytotoxic mediators, may have potential as prophylaxis for intimal hyperplasia. 5-Amino-levulinic acid-induced protoporphyrin IX (ALA-PPIX), a naturally occurring porphyrin precursor, and its product, -PPIX, offers a novel method of sensitization for PDT. We have investigated the pharmacokinetics of ALA in arteries and the effects of ALA-PPIX-sensitized PDT on normal and balloon-injured arteries.

METHODS AND RESULTS

ALA (20 to 200 mg/kg) was injected into healthy rats, and PPIX fluorescence was measured in the carotid arteries. In a second group of rats, the exposed carotid artery was laser illuminated (50 J/cm2, 630 nm) 30 to 90 minutes after sensitization. Three and 14 days after PDT, histological sections from treated arteries were analyzed by light microscopy. Subsequently, two new groups of rats underwent PDT (ALA, 100 mg/kg; laser, 50 J/cm2, 630 nm [at 60 to 90 minutes]). The left carotid arteries underwent balloon angioplasty by intraluminal passage of a Fogarty FG2 catheter immediately before irradiation. These rats were killed at 14 and 28 days together with laser-only, ALA-only, and untreated control rats. The arteries were perfusion-fixed in vivo. ALA-PPIX induced arterial media fluorescence in a dose-dependent manner. In the normal arteries, PDT produced a dose-dependent cellular depletion in the treated arterial segment at 3 days, and this was complete with 100 and 200 mg/kg of ALA. At 14 days, the media remained acellular, although the endothelial lining had regenerated. In the balloon-injured arteries, PDT produced complete inhibition of intimal hyperplasia at both 14 and 28 days (0%). This was significantly greater than that produced by any of the control rats (34% to 69% and 37% to 66% at the two times, respectively). Significance was at 99% using ANOVA and Fisher's PLSD test. No hemorrhage, thrombosis, or aneurysm formation was seen.

CONCLUSIONS

ALA-PPIX-sensitized PDT applied at the time of angioplasty effectively inhibits experimental intimal hyperplasia development in rats. This may offer a new approach to the management of angioplasty restenosis in patients.

Thallium imaging for brain tumors with results measured by a semiquantitative index and correlated with histopathology

BACKGROUND

The optimal management of patients with brain tumors requires knowledge of the tumor characteristics upon presentation and the discovery of recurrence after therapy. Thallium-201 (Tl-201) chloride has shown varying uptake in tumors, depending on their viability and the type and degree of malignancy. This study explores the diagnostic potential of thallium imaging in patients with brain tumors.

METHODS

Forty-three Tl-201 single photon emission computed tomographic scintigrams were performed on 40 patients with intracranial neoplasms, nearly equally divided between patients with no prior treatment and patients who had prior treatment and were suspected to have recurrent tumor and/or radiation necrosis. A thallium tumor index was calculated as the ratio of counts for a region of interest drawn in the lesion area and its mirror image in normal brain tissue. A two-tailed Student's t test was performed to compare the thallium index and histopathologic findings.

RESULTS

A value of 1.5 for the thallium tumor index allowed for the best correlation between the prediction of malignancy and the histopathologic results. In the pretreatment group, a thallium tumor index greater than 1.5 correlated with high grade malignancy, and less than 1.5 correlated with either a well differentiated astrocytoma or benign cyst. In the posttreatment group, a thallium tumor index greater than 1.5 correlated with recurrent and/or residual malignant tumor.

CONCLUSIONS

For those patients undergoing initial evaluation, the thallium study can help in the differential diagnosis of an intracranial mass lesion and offers confirmation of results of biopsy. For those patients who already have received treatment, the study can be used to detect recurrent or residual tumor.

Nonvisualization of suppressed thyroid tissue on Tl-201 scintigraphy

Tl-201 scintigraphy has been used to visualize thyroid tissue that is suppressed by an autonomously functioning thyroid nodule. Reports have indicated that the sensitivity of this technique rivals that obtained by I-123 scanning after thyroid-stimulating hormone stimulation. We report a case of triiodothyronine toxicosis caused by an autonomously functioning thyroid nodule in which the suppressed thyroid tissue was not visualized on Tl-201 scintigraphy. The suppressed tissue was readily identified with ultrasound imaging, which demonstrates the utility of this technique in differentiating between thyroid suppression and agenesis.

Therapeutic approaches to the control of fibrocellular intimal hyperplasia after angioplasty

Images

Nonpustular psoriatic lesions detected by Tc-99m HMPAO labeled granulocytes

A patient with a fever of unknown origin was evaluated by abdominal SPECT using Tc-99m HMPAO labeled granulocytes and a triple detector camera. Although no abscesses were located, nonpustular psoriatic skin lesions were demonstrated incidentally on the reprojectional images. Psoriatic scales contain a chemotactic factor for leukocytes, and this is a likely explanation for the increased uptake of the radiotracer by psoriatic lesions.

Action of calcitonin gene-related peptide upon bovine vascular endothelial and smooth muscle cells grown in isolation and co-culture

1. Bovine aortic endothelial cells (BAE) and smooth muscle cells (BASM) were grown separately and in co-culture. 2. Calcitonin gene-related peptide (CGRP) caused dose-dependent activation of adenylate cyclase in each cell type when grown in isolation. The concentration of CGRP causing half-maximal activation in BAE and BASM was 200 nM and 310 nM, respectively. 3. In cells grown in co-culture exposure to bradykinin produced dose-dependent elevations in cyclic GMP content which were maximal 1 min after application of the agonist. 4. CGRP (1 nM-1 microM) did not stimulate a rise in cyclic GMP in co-cultures. 5. Displaceable CGRP binding was identified throughout the wall of the bovine aorta. 6. We conclude that CGRP receptors coupled to adenylate cyclase are present on BAE and BASM, but there is no coupling of these receptors to the release of any agent (such as endothelium-derived relaxing factor) that activates guanylate cyclase.

Brown adipose tissue in lean and fat selection lines of sheep identified by immunodetection of uncoupling protein in western blots of tissue homogenates

1. Uncoupling protein (UCP) was purified from perirenal adipose tissue of 2-day-old lambs by a procedure involving Triton solubilization and hydroxyapatite treatment. It has an apparent Mr of 34,000. 2. Rabbit anti-sheep UCP and rabbit anti-rat UCP each cross-reacted with both rat and sheep UCP in Western blots, indicating that the major antigenic determinants of the sheep UCP and rat UCP are similar. 3. In Western blots, the anti-sheep UCP showed tissue specificity by detecting a band corresponding to UCP only in brown adipose tissue, but not in heart or liver homogenates. 4. The Western blotting procedure was used to analyse sheep tissues. UCP was detected in samples of perirenal, omental, back and lymph node fat from 2-day-old lambs, but not in heart, liver, muscle or kidney samples. 5. UCP was not detected in any tissue samples from 34-day-old or 7-month-old lambs. 6. Comparison of the amount of UCP in perirenal fat of 2-day-old lambs from lean, fat and control selection lines, using the Western blotting procedure, showed no apparent difference.

Human calcitonin gene-related peptide activates adenylate cyclase and releases prostacyclin from human umbilical vein endothelial cells

1 Endothelial cells of human umbilical vein were isolated and cultured in vitro. 2 In these cells there was a concentration-dependent release of prostacyclin and activation of adenylate cyclase by human calcitonin gene-related peptide (hCGRP). The concentration of hCGRP for half-maximum activation of adenylate cyclase (Kact) by hCGRP was 190 nM. 3 Bradykinin induced a ten fold greater release of prostacyclin than CGRP, but did not activate adenylate cyclase. 4 hCGRP may exert its potent vasodilator properties by stimulating release of vasorelaxant substances, including prostacyclin from endothelial cells.

Calcitonin gene-related peptide: a potent dilator of human epicardial coronary arteries

To investigate the action of calcitonin gene-related peptide (CGRP) on human epicardial coronary arteries, six patients received intracoronary CGRP at doses of 50,100, and 200 ng/min. The effect of CGRP was measured angiographically with a computerized analysis system. A dose-dependent increase in coronary arterial diameter was observed. At the highest dose there were 34%, 7%, 38%, and 40% mean increases in the diameters of the circumflex, proximal, mid, and distal left anterior descending arteries, respectively. No further increase in diameter was found after a subsequent dose of 1 mg intracoronary isosorbide dinitrate. Prior infusion of CGRP did not prevent coronary arterial spasm induced by ergonovine in two patients with variant angina, but a subsequent bolus of CGRP partially relieved the spasm. We propose that CGRP has a role in the regulation of coronary vascular smooth muscle tone.

IOLSTAT--a program for comprehensive intraocular lens equation comparison with statistical analysis

A computer program that will simultaneously solve five of the major intraocular lens (IOL) equations predicting the primary implant power required for emmetropia or ametropia is presented. The program can, alternatively, predict the degree of ametropia given the power of an IOL. The resultant predictions are analyzed using weighted and unweighted statistics, predicting a mean and a standard deviation. The results are displayed in a table which lists the prediction and the percent deviation from the weighted mean for each equation. The program features automatic averaging of keratometer readings, ultrasound axial length corrections, and an algorithm for estimating postoperative anterior chamber depth.

Smoking, age and the pill

A brief outline is given of alterations in the normal physiology caused by cigarette smoking, aging and taking combined oral contraceptive pills. There are similarities in some of these effects. Evidence is considered regarding the health risks of using the pill and the relationship of these risks to the age of the woman and her smoking habit. This evidence is derived from recent epidemiologic studies carried out in Britain on some aspects of morbidity and the death rates ascribable to the pill. The implications for prescribing clinicians are discussed and indications are given for reducing the overall risks to life and health for pill users.

The British retrospective and prospective studies

The clinician needs scientific evidence to enable him to advise patients efficiently and correctly. The sources of this evidence are listed and the part played by each discussed. The rarity of adverse effects from the use of oral contraceptive pills entails the need to make use of epidemiologic studies. The different types of study are briefly described, with examples from recent work carried out in Britain. The advantages and problems of interpretation associated with each are discussed. The present position taken by United Kingdom doctors working in the field of contraceptive practice is summarized.

Social classes for women of differing marital status

Studies involving collation of social characteristics of women frequently include statements about their social class designation and may compare groups in different classes against other variables. The method of making such a designation is very unsatisfactory and may lead to spurious conclusions arising from the method of classification.

When designation is carried out by a method primarily concerned with married women's own occupations rather than those of their husbands, some of the apparent differences in distribution are lost. It is possible to examine married and unmarried women together if those in both groups work outside the home.

Such considerations are particularly important in data relating to reproductive behaviour, such as abortion statistics and studies of births or the use of contraception.