Inheritance of avermectin resistance in Haemonchus contortus

A larval development assay was used to compare the responses of the Chiswick Avermectin Resistant (CAVRS) isolate of Haemonchus contortus, an avermectin-susceptible isolate (VRSG) and their crosses to avermectins. The F(1) and F(2) generations of reciprocal crosses between CAVRS and VRSG were denoted as CAVRS malesxVRSG females=CXV, and VRSG malesxCAVRS females=VXC. The levels of avermectin resistance in the developing larvae of the F(1) of both CXV and VXC were indistinguishable from that in the avermectin-resistant parent, indicating that the resistance trait is completely dominant. Avermectin dose-response curves for the CXV F(1) did not show a 50% mortality rate at low concentrations, indicating that avermectin resistance is not sex-linked. This conclusion was confirmed when adult male worms of the F(1) of the CXV mating were found to have survived treatment of the host with 200microgkg(-1) ivermectin. This dose rate (200microgkg(-1) ivermectin) caused a 50% reduction in the number of adult males in the F(1) from both CXV and VXC crosses, but only a non-significant reduction in the number of adult females in the F(1). Dose-response curves obtained for the F(2) generations in the larval development assay indicated the presence of 25% of avermectin-susceptible individuals, suggesting that a single major gene largely controls the avermectin-resistance trait. This genetic analysis of avermectin resistance in an Australian H. contortus isolate indicates that the expression of the gene for avermectin resistance is an autosomal, complete dominant in the larvae; however, in adults its expression is sex-influenced, with males having a lower resistance to avermectin than females.

Plasma from women with pre-eclampsia induces an in vitro alteration in the endothelium-dependent behaviour of myometrial resistance arteries

OBJECTIVE

To compare the in vitro effect of plasma from normal pregnant women and women with pre-eclampsia on the endothelium-dependent behaviour of myometrial resistance arteries from normal pregnant women.

DESIGN

An in vitro comparative study.

SETTING

Nottingham City Hospital.

SAMPLE

Uterine biopsy specimens were obtained from normal pregnant women delivered by elective caesarean section at term. Plasma was collected from nulliparous women with pre-eclampsia (n = 18), and from multiparous normal pregnant women (n = 18), all samples being matched for maternal age and gestation at venepuncture. Pools of plasma from women with pre-eclampsia and normal pregnant women were formed from these samples and were used in all the experiments.

METHODS

Myometrial resistance vessels obtained from the uterine biopsies were incubated with normal pregnant plasma, plasma from women with pre-eclampsia, or without plasma. Wire myography was employed to study the effect of plasma on the endothelium-dependent behaviour of these vessels.

RESULTS

Incubation of vessels from normal pregnant women with plasma from women with pre-eclampsia resulted in a significant reduction in endothelium-dependent relaxation, compared with vessels incubated either with plasma from normal pregnant women or without plasma. This alteration in endothelial function occurred after an incubation period of one hour and required a threshold concentration for its effect to become established. Removal of the vascular endothelium abolished these changes in vessel behaviour. There were no plasma-induced alterations in the endothelium-independent behaviour of the vascular smooth muscle.

CONCLUSIONS

This study supports the hypothesis that plasma from women with pre-eclampsia is capable of altering endothelium-dependent myometrial relaxation in vessels from pregnant women.

Attitudes of carers and the elderly occupants of residential homes to antimicrobial chewing gum as an aid to oral health

OBJECTIVE

The aim of this study was to investigate the attitudes of elderly residents to using an antimicrobial chewing gum as an aid to oral health, and the opinion of their carers on such a procedure.

DESIGN

A cross-sectional, multi-centre survey using a structured interview/questionnaire conducted with elderly residents and their carers.

SETTING

In January 1998, 9 residential/nursing homes were chosen at random from all the homes in West Hertfordshire, 207 residents were asked to chew two pieces of gum twice daily for 7 days.

SUBJECTS

The participants, 148 women and 59 men, were aged between 53-100 years (mean age 82.23 +/- 9.62 years). 47 carers, all female, were involved in distributing and collecting the gum.

RESULTS

122 residents (58.9%) were edentulous and 85 (41%) of the participants were partially dentate. Of those with teeth 23 (27%) had 21 teeth or more. 73 (35.2%) residents found that chewing the gum was difficult with 37 (17.9%) of this group being unable to chew (P < 0.0001 for those residents with no teeth/dentures or dentures unopposed by teeth or other dentures). 32 (18.6%) subjects disliked the flavour of the gum. Of the 170 residents who chewed the gum 99 (57.2%) found it reduced oral dryness and 78 (45.1%) reported it made their mouth feel healthy. 34 (53.6%) of the dentate and 47 (40.9%) of the edentate residents wished to keep using the gum (P < 0.05). 35 (74.5%) of the carers found it easy to distribute the gum and 29 (61.7%) thought that chewing gum was an acceptable method of maintaining oral health for residents.

CONCLUSION

The antimicrobial gum investigated in this study was acceptable to many elderly occupants and their carers, significantly improving perceived oral health and oral dryness of residents.

D-dimer for the exclusion of venous thromboembolism: comparison of a new automated latex particle immunoassay (MDA D-dimer) with an established enzyme-linked fluorescent assay (VIDAS D-dimer)

The use of D-dimer tests to exclude venous thromboembolism is an important advance in clinical practice and also has economic benefits. Ideally the test should be objective and a test that could be run on the routine coagulometer would obviate the need for additional investment in alternative hardware. A new automated latex particle immunoassay (MDA D-dimer) that can be run on a routine coagulometer was compared with a well established enzyme linked fluorescent assay (VIDAS D-dimer) on the basis of their ability to exclude venous thromboembolism. The assays were compared in 49 patients presenting to the emergency department with clinically suspected deep vein thrombosis or pulmonary embolism. After objective diagnostic imaging, 20 patients were confirmed to have venous thromboembolism. There was strong agreement between the assays in individual patients. Using a cut-off of 500 micrograms/l, both tests had a sensitivity of 100% and therefore a negative predictive value of 100%, however the MDA test would have spared more patients (20% vs. 12%) from further testing if a negative D-dimer was used to rule-out the diagnosis. It was concluded that a rapid, objective latex D-dimer test run on a routine coagulometer (MDA D-dimer) can be used to exclude the diagnosis of venous thromboembolism.

VEGF via VEGF receptor-1 (Flt-1) mimics preeclamptic plasma in inhibiting uterine blood vessel relaxation in pregnancy: implications in the pathogenesis of preeclampsia

Preeclampsia is a multisystem disorder characterized by hypertension and proteinuria. There is accumulating evidence that this is a disease of the endothelium, with an as-yet unidentified circulating factor, or factors, causing the observed alteration in vascular function. We previously reported that the function of myometrial vessels is altered on exposure to plasma from women with preeclampsia. Vascular endothelial growth factor (VEGF) is an angiogenic growth factor that acts via two high-affinity receptors (KDR and Flt-1), and its production is increased in preeclampsia. Here we report that VEGF and its Flt-1 receptor may play a pivotal role in the altered vascular function of preeclampsia. Myometrial resistance vessels were obtained at the time of cesarean section. Using the Mulvany wire myograph, the endothelium-dependent behavior of these vessels was studied. Incubation of vessels from pregnant women with VEGF resulted in a reduction of endothelium-dependent relaxation that mimicked the reduction induced by plasma from women with preeclampsia. The altered function that occurred upon exposure of vessels to VEGF or plasma from women with preeclampsia did not occur when plasma was incubated with antibodies to VEGF before vessel incubation. The presence of an anti-KDR receptor antibody had no effect on VEGF response. However, in the presence of an anti-Flt-1 receptor antibody, VEGF or plasma from women with preeclampsia no longer attenuated the endothelium-dependent relaxation (p < 0.05). The changes observed with VEGF and plasma from women with preeclampsia and their subsequent blockade with anti-VEGF antibody and anti-Flt-1 receptor antibody strongly suggest that VEGF acting through the Flt-1 receptor is pivotal in the pathogenesis of this disease.

Fetal brain activity demonstrated by functional magnetic resonance imaging

Functional magnetic resonance imaging was used to study fetal brain activity. This activity was in response to an auditory stimulus.

Role of accurate mass measurement (+/- 10 ppm) in protein identification strategies employing MS or MS/MS and database searching

We describe the impact of advances in mass measurement accuracy, +/- 10 ppm (internally calibrated), on protein identification experiments. This capability was brought about by delayed extraction techniques used in conjunction with matrix-assisted laser desorption ionization (MALDI) on a reflectron time-of-flight (TOF) mass spectrometer. This work explores the advantage of using accurate mass measurement (and thus constraint on the possible elemental composition of components in a protein digest) in strategies for searching protein, gene, and EST databases that employ (a) mass values alone, (b) fragment-ion tagging derived from MS/MS spectra, and (c) de novo interpretation of MS/MS spectra. Significant improvement in the discriminating power of database searches has been found using only molecular weight values (i.e., measured mass) of > 10 peptide masses. When MALDI-TOF instruments are able to achieve the +/- 0.5-5 ppm mass accuracy necessary to distinguish peptide elemental compositions, it is possible to match homologous proteins having > 70% sequence identity to the protein being analyzed. The combination of a +/- 10 ppm measured parent mass of a single tryptic peptide and the near-complete amino acid (AA) composition information from immonium ions generated by MS/MS is capable of tagging a peptide in a database because only a few sequence permutations > 11 AA's in length for an AA composition can ever be found in a proteome. De novo interpretation of peptide MS/MS spectra may be accomplished by altering our MS-Tag program to replace an entire database with calculation of only the sequence permutations possible from the accurate parent mass and immonium ion limited AA compositions. A hybrid strategy is employed using de novo MS/MS interpretation followed by text-based sequence similarity searching of a database.

Significance of fatty acids in pregnancy-induced immunosuppression

Pregnancy can exert suppressive effects on chronic inflammatory conditions. We have previously demonstrated a depression in polymorphonuclear leukocyte (PMN) respiratory burst during pregnancy which could explain this amelioration. To elucidate the biochemical mechanism, we have examined PMN phospholipase A2 (PLA2) activity and its relationship to cellular and circulating fatty acids in pregnant women (30 to 34 weeks) and nonpregnant controls. PMN PLA2 activity was determined by arachidonic acid (AA) and leukotriene B4 (LTB4) release, respiratory burst activity was determined by lucigenin-enhanced chemiluminescence, and total serum and PMN fatty acid levels were determined by gas-liquid chromatography. AA release was significantly reduced for pregnancy PMNs in response to N-formyl-met-leu-phe (fMLP) under unprimed and tumor necrosis factor alpha (TNF-alpha)- or interleukin 8-primed conditions. Similarly, LTB4 liberation was significantly reduced in response to fMLP and phorbol myristate acetate in unprimed and TNF-alpha-primed pregnancy PMNs. All major fatty acid classes were altered in the pregnant state. Of these differences in PMNs, oleic acid and alpha-linolenic acid showed a significant increase (13 and 26%, respectively) and stearic acid and AA showed a significant decrease (8 and 30%, respectively). The stearic acid, oleic acid, and AA compositions of all cells analyzed correlated with their corresponding changes in serum fatty acid levels. Crossover serum incubations modified both fatty acid profiles and the PMN respiratory burst accordingly, while individual fatty acid incorporation studies highlighted the importance of polyunsaturated fatty acids for NADPH oxidase efficiency. These findings indicate that the attenuation of PMN function in pregnancy may originate from a reduction in the available pool of cellular fatty acids. Furthermore, this reduction arises as a direct result of a pregnancy-induced shift in circulating fatty acids from polyunsaturated to monounsaturated forms.

Stemming the tide: reducing cardiovascular disease and renal failure in Australian Aborigines

An epidemic of cardiovascular disease (CVD) and end stage renal disease (ESRD) has developed among Aborigines in the Northern Territory; CVD deaths increased over the 1980s (tripling among women!), and are now more than five times those of non-Aboriginal people, while ESRD rates are increasing more than 20-fold and are doubling every three to four years. Dialysis costs (>$75,000 per person/year) pose a crisis for health care budgets, but premature mortality is the greater human catastrophe. Health services are not meeting the challenge of timely diagnosis, prevention and containment. We screened 90% of adults (20+ years) in one community, with CVD mortality among the highest in Australia, and ESRD rates increased 60-fold. Seventy-five per cent of persons were smokers. Central obesity was common, but BMIs only modestly increased by Caucasian standards, 23% had hypertension (>140/90), 29% had diabetes or impaired glucose tolerance (IGT) (peaking at 65% of persons aged 40-49 years), high triglyceride and insulin levels were common, and 55% had albuminuria (albumin/creatinine ratio (ACR), >3.4 gm/moL). Progressive albuminuria predicted renal failure. ACR was correlated with age, BMI, blood pressure, lipid, glucose and insulin levels, heavy drinking and past and current skin infections, and, inversely with birth weight. ACR correlated strongly with a composite CV risk score, and in a two to five year follow-up, microalbuminuria (ACR 3.4-33) and overt albuminuria (ACR 34+) have both predicted increased rate of premature death from natural causes of lower ACRs. Thus albuminuria marks CV risk/disease. This implies that renal and CV disease share common risk factors, and should respond to the same interventions, and that this response might be monitored through ACR levels. Robust public health programmes could reduce all these reversible risk factors, lowering disease rates over the intermediate term, however, few such programmes are in place. Modification of disease in persons already afflicted is a parallel responsibility. To this end, in November 1995, we introduced a treatment programme with Coversyl (perindopril, Servier) for all persons in the study community with hypertension (>140/90), for all diabetics with ACR 3.4+ and for all nondiabetic, non-hypertensive persons with progressive overt albuminuria (ACR 34+). One-quarter of all adults, or 224 persons have enrolled; 162 have reached one year of treatment and 100 have passed two years. Compliance is reasonable and enthusiasm high. Average SBP has fallen 12 mmHg (24 mmHg in hypertensive persons), while average ACR and estimated glomerular filtration rate (GFR) have stabilised. This contrasts favourably with the pretreatment course (average 2.7 years) in the same persons, when SBP had increased by 3 mmHg, ACR had increased by 15% and GFR had decreased by 3.5 mL/min each year. Cautious estimates suggest a >50% fall in ESRD, and a reduction in all-cause and CV deaths, even at this early stage, although more extended observation is needed. These data predict a dramatic and rapid fall in morbidity, premature deaths and health care costs if these basic principles of medical care are extended to all Aboriginal people. A national, concerted, multi-disciplinary effort to implement a coherent, effective strategy to this end is of great urgency.

Prevalence of the factor VLeiden mutation among autopsy patients with pulmonary thromboembolic disease using an improved method for factor VLeiden detection

Activated protein C resistance caused by factor VLeiden mutation is the most common inherited predisposing cause of venous thromboembolism, including pulmonary embolism (PE). We studied whether the incidence of factor VLeiden is higher among patients with PE evident at autopsy than in the general population. Paraffin-embedded fixed tissue blocks from all autopsy patients with diagnosed pulmonary thromboembolic disease during a 4-year period were collected for DNA extraction. Extraction and molecular analysis of the DNA was performed with an improved technique with an internal control to determine the presence of factor VLeiden mutation. Analysis of 82 autopsy cases with PE yielded 5 patients who were heterozygotes. Seventy-seven of the 82 patients analyzed were normal, and no homozygotes for factor VLeiden mutation were identified. This yielded a positive rate of 6% overall and 7% among white patients, which is similar to the incidence of heterozygotes in the white population. This study indicates that routine determination of factor VLeiden mutation is not warranted for patients with PE diagnosed at autopsy.

Lymphatic and hematopoietic cancer in teachers

A recent study found high rates of leukemia and related disorders among teachers. This finding may be related to exposure to childhood infections. Therefore, epidemiologic studies on the risk of lymphatic and hematopoietic cancer among teachers were systematically reviewed. Altogether 26 relevant investigations were identified, most from ad hoc publications rather than from scientific journals. Elevated risks of leukemia, lymphoma, and multiple myeloma were found in studies using proportional mortality or mortality odds ratios as outcome measures. However, these observations may reflect low overall mortality and do not necessarily indicate high death rates from the cancers of interest. In studies deriving standardized mortality or incidence ratios, the risk estimates were generally lower. The most striking finding was for non-Hodgkin's lymphoma (approximate summary relative risk 1.36, 95% confidence interval 1.13-1.62), but it was likely to have been exaggerated by publication bias. In conclusion, no compelling epidemiologic evidence exists for a hazard of leukemia or related diseases among teachers.

Preeclampsia: the endothelium, circulating factor(s) and vascular endothelial growth factor

It has been proposed that endothelial cell activation is the primary event in the multisystem disorder of preeclampsia. Evidence for endothelial involvement in this condition abounds. The best-characterized morphologic abnormality of this syndrome, glomerular endotheliosis, involves endothelial cells. Also associated with preeclampsia is a loss of endothelial cell integrity, with the consequent increase in vascular permeability, and an increase in the circulating levels of the endothelial cell markers, fibronectin, von Willebrand factor, tissue plasminogen activator, and plasminogen activator inhibitor-1. It is now well documented that endothelial activation contributes to the coagulation abnormalities observed in this disease. There is much evidence that the endothelial alterations in preeclampsia result from one or more circulating factors. The incubation of cultured endothelial cells with serum or plasma samples, taken from normal pregnant women and women with preeclampsia, results in marked alterations in cell behavior and metabolic processes. More recently, experiments employing myographic techniques have demonstrated convincingly the effects of a circulating factor(s) on the function of endothelial cells of resistance arteries. Vascular endothelial growth factor (VEGF) possesses many of the characteristics required of a candidate circulating factor. It contains a hydrophobic secretory signal sequence, exerts in vitro effects specific to vascular endothelial cell, and promotes endothelial expression of procoagulant activity. Circulating VEGF concentrations are elevated in women with preeclampsia, and VEGF increases microvascular endothelial cell prostacyclin production in a dose-dependent manner, analogous to the acute effects of plasma from patients with preeclampsia. Similarly, in myographic studies, when myometrial resistance arteries are incubated with VEGF, there are dose-dependent alterations in endothelium-dependent behavior, mirroring those found after incubation with plasma from patients with preeclampsia.

A species-specific monoclonal antibody to Cynodon dactylon

BACKGROUND

It is usually difficult to differentiate between the pollens of different grass species on the basis of their appearance under a microscope, as they often appear similar. Such distinctions are important when interpreting the clinical relevance of pollens in air samples as individuals can differ in their allergic responses to different grass species. As this allergenic distinction occurs at the level of presence and differences of epitopes on the allergens associated with different species, it could be anticipated that species-specific monoclonal antibodies could provide such distinctions between pollens.

METHOD

Monoclonal antibodies raised against Cynodon dactylon were screened and characterised in ELISA assays and blotting, using a range of grass pollen extracts, to identify clones which were species specific.

RESULTS

The most specific monoclonal raised to C. dactylon did not react at a level of greater than 1.2% to extracts of 10 other grass pollens in a direct ELISA assay and showed no detectable cross-reactivity in a particle blotting assay.

CONCLUSION

It has been possible to produce a monoclonal antibody that is functionally species specific to C. dactylon.

Clinical characteristics of sudden death victims in heritable (chromosome 1p1-1q1) conduction and myocardial disease

OBJECTIVES

The purpose of this study was to identify the clinical characteristics of family members at risk of sudden death.

BACKGROUND

The significance of sudden death in heritable cardiac disorders with delayed expression is incompletely understood. Additional insights come from a four-decade experience of seven generations of a family of German origin with autosomal dominant (chromosome 1p1-1q1) cardiac conduction and myocardial disease.

METHODS AND RESULTS

A total of 38 family members (20 males; 18 females) were identified with sudden death. Twenty-eight family members (mean age 48+/-8 years) from earlier generations had no pacemaker at the time of sudden death. In this group, 15 subjects were asymptomatic prior to sudden death. Ten family members with sudden death, from later generations, had chronically implanted pacemakers for high grade atrioventricular block. This group was older (mean age 57+/-2 years), with decreased functional status (New York Heart Association class II to IV), enlarged left atria, dilated left ventricles with reduced systolic function and documented ventricular fibrillation in three members. Twenty-eight family members with sudden death were descendants of sib lineages 2 or 6; 21 family members with sudden death were offspring of a parent who also suffered sudden death.

CONCLUSION

Sudden death is an important late outcome in heritable (chromosome 1p1-1q1) cardiac conduction and myocardial disease. Pacemaker therapy is important for the treatment of symptomatic bradycardia, but it does not prevent sudden death. Family members who are beyond the third decade of life with reduced functional capacity, left ventricular dysfunction, pacemakers and who are the offspring of a parent with sudden death appear to be at greatest risk

Effect of catheter tip length and position on lesion volume in temperature controlled RF ablation in canine tricuspid valve annulus

BACKGROUND

Radiofrequency (RF) energy has been delivered to the tricuspid valve annulus (TVA) in humans with both 4 mm and 8 mm long catheter tip electrodes to treat atrial flutter. However, lesion volume with temperature controlled RF delivery systems has not been previously characterized.

METHODS

In 10 anesthetized canines, a single pulse of temperature controlled RF energy at a 70 degrees C set point, 30 second duration was delivered with either a 7 Fr/4 mm tip or a 7 Fr/8 mm tip electrode in a position both anterolateral and posteroseptal to the tricuspid valve annulus (TVA). Surface echocardiogram was obtained prior and after ablation. The animals were sacrificed after ablation and the lesions underwent gross and histological examination.

RESULTS

Lesion size, tip temperature and power were related to tip electrode surface area (SA). Eight mm tips (SA = 59 mm2) tended to create significantly larger lesions than 4 mm tips (SA = 29 mm2). Median lesion volume was 22 vs. 1.5 mm3, respectively. Eight mm tips were also associated with higher power requirements and lower temperatures than 4 mm tips. Posteroseptal TVA lesions tended to be larger than anterolateral lesions. No significant complications were noted.

CONCLUSIONS

Using temperature controlled RF ablation, large lesions may be safely created on the canine TVA using 7 Fr catheters with 8 mm long tips.

Hoarding and treatment response in 38 nondepressed subjects with obsessive-compulsive disorder

OBJECTIVE

The authors studied factors associated with short-term treatment response in 38 nondepressed subjects with DSM-III-R obsessive-compulsive disorder (OCD).

METHOD

The subjects completed 12 weeks of treatment with paroxetine (N = 20), placebo (N = 8), or cognitive-behavioral therapy (N = 10). Clinician and self-rated measures were gathered at baseline, during treatment, and after treatment.

RESULTS

Seventeen (45%) subjects had "much" or "very much" improvement and achieved at least a 40% decrease in their total Yale-Brown Obsessive Compulsive Scale (Y-BOCS) score. Responders had lower obsessive-compulsive scores on the Symptom Checklist 90-Revised, had a lower checking score on the Maudsley Obsessive-Compulsive Inventory, were less likely to have had prior drug therapy, and in general suffered more obsessive-compulsive symptoms. They were significantly less likely to have hoarding obsessions and corresponding compulsions. The latter finding was confirmed using multiple regression analysis.

CONCLUSION

Hoarding is an important symptom that predicts poor treatment response in patients with OCD.

Autism and tuberous sclerosis complex: prevalence and clinical features

This study employed a hierarchical assessment to detect the prevalence of autism in a clinic sample of individuals with tuberous sclerosis complex (TSC). After screening subjects with the Autism Behavior Checklist, subsequent evaluations with the Autism Diagnostic Interview, and direct clinical observation, the prevalence of autistic disorder in this sample of 20 subjects was conservatively estimated at 20%. Data suggest a possible association between both hypsarrythmia and TSC-related cardiac abnormalities with autism in this subgroup of TSC individuals. Implications of these findings for clinical practice and further research are discussed.

Glucose transport inhibitors protect against 1,2-cyclohexanedione-produced potassium loss from human red blood cells

It has been suggested that the glucose transport system of human erythrocytes contains an arginine shield to prevent the leak of potassium through the transporter. To investigate this suggestion we treated human erythrocytes with the specific arginine reagent 1,2-cyclohexanedione. Under conditions which produce a covalent reaction between arginine and the reagent, a steady leak of potassium occurs. If glucose, maltose or the inhibitor phloretin are present during the reaction the extent of the leak is reduced. These findings support the view that arginines have a role in preventing potassium loss through the glucose transporter.

Fetal development of Leydig cell activity in the mouse is independent of pituitary gonadotroph function

During fetal development the testes secrete anti-Mullerian hormone and testosterone to induce formation of the male phenotype. Adult Leydig cells secrete testosterone under the control of LH, but the role of the fetal pituitary in regulating fetal Leydig cell function is unclear. To study the early relationship between pituitary and Leydig cell function, we have examined the development of fetal pituitary LH levels and Leydig cell function in normal mice and in hypogonadal (hpg) mice that lack GnRH and, thus, circulating gonadotropins. In normal and hpg mice, pituitary LH content was barely detectable until embryonic day 17 (E17), when levels began to increase significantly in both groups. Pituitary levels of LH in hpg mice were, however, only about 10% of normal at all ages. Full-length LH receptor transcripts were first detectable in fetal testes on E16 in both normal and hpg mice. In normal mice, levels of testicular messenger RNA (mRNA) encoding cytochrome P450 side-chain cleavage and 17alpha-hydroxylase increased from E13 to reach a peak around birth. In hpg mice, levels of mRNA encoding these enzymes were normal until around birth, at which time there was a significant decline. Levels of testicular mRNA encoding 3beta-hydroxysteroid dehydrogenase type I were similar in normal and hpg mice and showed little change during development. Intratesticular testosterone reached a peak on E18 in normal animals before declining again after birth. In hpg mice, intratesticular testosterone levels were normal throughout fetal development and on the day of birth, but were barely detectable by postnatal day 5. Results show 1) that fetal Leydig cell function in the mouse is normal in the absence of endogenous circulating gonadotropins; 2) that Leydig cells become dependent on gonadotropins shortly after birth; and 3) that pituitary LH synthesis can start in the absence of GnRH but is dependent on LH for a normal level of synthesis and secretion.