Effect of Holstein genotype on innate immune and metabolic responses of heifers to lipopolysaccharide (LPS) administration

Heifers (n = 4/genotype) from unselected (stable genotype since 1964, UH) and contemporary (CH) Holsteins that differed in milk yield (6,200 and 11,100 kg milk/305 d) were used to assess the impact of selection on innate immune and acute-phase response to an endotoxin (lipopolysaccharide; LPS). Jugular catheters were implanted 24 h before LPS administration. Blood samples were collected at -1, -0.5, 0, 1, 2, 3, 4, 6, 8, and 24 h relative to iv administration of 0.5 μg LPS/kg BW. Rectal body temperature (BT) was determined at these sampling times and at 5 and 7 h. Dermal biopsies were collected after the 24 h blood sample and processed to isolate fibroblasts. Plasma was analyzed for tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), serum amyloid A (SAA), xanthine oxidase (XO), and nitrate + nitrite (NOx), cortisol, glucose, and IGF-1 content. Isolated fibroblasts were exposed to IL-1β or LPS and IL-6 and IL-8 content of culture media determined. Exposure to LPS increased BTs and plasma concentrations of TNF-α, IL-6 SAA, XO, cortisol, and glucose (P < 0.05) in both genotypes. Plasma concentrations of TNF-α, XO, NOx, and glucose did not differ (P > 0.25) between the genotypes, but IL-6 and SAA concentrations were reduced (P < 0.05) in CH relative to UH heifers while cortisol and IGF-1 concentrations tended (P < 0.08) to be reduced in CH heifers. After 36 h exposure to LPS, concentrations of IL-6 were greater (P < 0.05) in culture media from incubations of CH than UH fibroblasts but concentrations of IL-8 did not differ between genotypes. There was a trend (P = 0.08) for IL-8 concentrations to be reduced in media from CH fibroblasts exposed to IL-1β for 24 h but IL-6 concentrations did not differ between genotypes. Results indicate 50 yr of selection has reduced the robustness of the innate immune and acute-phase response to LPS in the contemporary Holstein heifer.

Neutrophil maturation rate determines the effects of dipeptidyl peptidase 1 inhibition on neutrophil serine protease activity

Background and Purpose

Neutrophil serine proteases (NSPs) are activated by dipeptidyl peptidase 1 (DPP1) during neutrophil maturation. The effects of neutrophil turnover rate on NSP activity following DPP1 inhibition was studied in a rat pharmacokinetic/pharmacodynamic model.

Experimental Approach

Rats were treated with a DPP1 inhibitor twice daily for up to 14 days; NSP activity was measured in onset or recovery studies, and an indirect response model was fitted to the data to estimate the turnover rate of the response.

Key Results

Maximum NSP inhibition was achieved after 8 days of treatment and a reduction of around 75% NSP activity was achieved at 75% in vitro DPP1 inhibition. Both the rate of inhibition and recovery of NSP activity were consistent with a neutrophil turnover rate of between 4–6 days. Using human neutrophil turnover rate, it is predicted that maximum NSP inhibition following DPP1 inhibition takes around 20 days in human.

Conclusions and Implications

Following inhibition of DPP1 in the rat, the NSP activity was determined by the amount of DPP1 inhibition and the turnover of neutrophils and is thus supportive of the role of neutrophil maturation in the activation of NSPs. Clinical trials to monitor the effect of a DPP1 inhibitor on NSPs should take into account the delay in maximal response on the one hand as well as the potential delay in a return to baseline NSP levels following cessation of treatment.

A longitudinal study of the effect of heparin thromboprophylaxis during pregnancy on maternal bone metabolism

The aim of this study was to determine the effect of heparin thromboprophylaxis during pregnancy on maternal biochemical markers of bone metabolism. This was a prospective longitudinal study of carboxy terminal pro-peptide of type I collagen (PICP) and cross-linked carboxyterminal telopeptide of type I collagen (ICTP) levels in 15 women, who had heparin thromboprophylaxis during pregnancy compared with those of 18 normal pregnant controls. During pregnancy, the rate of change of PICP and ICTP in women who had heparin thromboprophylaxis was similar to those of women who did not (P = 0.184 for PICP, and P = 0.129 for ICTP), and PICP and ICTP levels at individual time points were similar in both groups. Therefore, heparin thromboprophylaxis during pregnancy does not affect maternal biochemical markers of bone metabolism.

Determinants of 25-hydroxyvitamin D levels in African-American and Caucasian male veterans

SUMMARY

Among 307 males seen in VA Medical Center, independent determinants (p < 0.01 for all) of serum 25-hydroxyvitamin D [25(OH)D] levels included race, vitamin D supplements, BMI, dietary calcium intake and smoking, but not age. Negative association between 25(OH)D and parathyroid hormone (PTH) was similar for Caucasian and African-American men.

INTRODUCTION

In this prospective cohort study, we examined determinants of serum 25-hydroxyvitamin D [25(OH)D] levels and the relationship between 25(OH)D and PTH levels and body mass index (BMI).

METHODS

Male veterans (n = 307) were recruited at a VA Medical Center. Serum levels of PTH and 25(OH)D were obtained. Surveys and chart reviews were completed. Vitamin D insufficiency was defined as 25(OH)D <30 ng/ml. Univariate and multivariate regression analyses were performed.

RESULTS

Among 232 African-American (AA) men (mean +/- SD), 25(OH)D level (21.4 +/- 10.4 ng/ml) was lower and prevalence of insufficiency (80%) was higher than among 75 Caucasians (C; 28.5 +/- 11.1 ng/ml and 53%, respectively, p < 0.01 for both). In multivariate regression analysis, independent determinants (p < 0.01 for all) of 25(OH)D levels included AA race, vitamin D supplements, BMI, dietary calcium intake, and smoking. Despite lower 25(OH)D levels in African-Americans, PTH levels were similar to those seen in Caucasians. There was a significant (p < 0.02) negative linear association between 25(OH)D and PTH in African-American (r(2) = 0.05) and Caucasian (r(2) = 0.08) men, and there was no difference between the slopes of the relationship.

CONCLUSIONS

25(OH)D levels are determined by modifiable risk factors such as vitamin D supplementation in both AA and C males. The negative association between 25(OH)D and PTH is similar between the two races.

Mutation scanning of the p53 tumor suppressor gene in renal and liver transplant patients in Hungary

INTRODUCTION

The increased incidence of malignancies among transplanted patients is well known. Abnormal function of the p53 tumor suppressor gene has been reported in more than half of all tumors. The aim of our study was to detect point mutations of p53 gene in transplanted patients because the presence of mutations may be a predictive factor for tumor development. An earlier diagnosis can help to develop new strategies for immunosuppressive therapies.

METHODS

Three point mutations were chosen based on the literature: exon5-codon175, exon7-codon248, exon8-codon273. Genomic DNA from the plasma of 60 liver, 362 renal transplants, and 45 nontransplanted patients with different tumors and 20 suspected healthy patients were analyzed with a real-time PCR method using the Roche LightCycler. The mutations were evaluated by melting curve analysis.

RESULTS

We elaborated a special protocol for scanning the above mentioned p53 point mutations, which were proved by sequencing as well. Among 487 patients, 486 showed a wild-type genotype. The only patient carrying a mutation at codon 273 (heterozygous) was a liver transplant patient, who developed pancreas carcinoma and had already died.

CONCLUSION

Our data suggest that mutations of the targeted codons in leukocyte DNA seem to be rare, but a mutation could be lethal. The evaluated three point mutations of p53 gene were not predictive for tumor development.

Apoptotic mimicry: an altruistic behavior in host/Leishmania interplay

Apoptosis is the most common phenotype observed when cells die through programmed cell death. The morphologic and biochemical changes that characterize apoptotic cells depend on the activation of a diverse set of genes. Apoptosis is essential for multicellular organisms since their development and homeostasis are dependent on extensive cell renewal. In fact, there is strong evidence for the correlation between the emergence of multicellular organisms and apoptosis during evolution. On the other hand, no obvious advantages can be envisaged for unicellular organisms to carry the complex machinery required for programmed cell death. However, accumulating evidence shows that free-living and parasitic protozoa as well as yeasts display apoptotic markers. This phenomenon has been related to altruistic behavior, when a subpopulation of protozoa or yeasts dies by apoptosis, with clear benefits for the entire population. Recently, phosphatidylserine (PS) exposure and its recognition by a specific receptor (PSR) were implicated in the infectivity of amastigote forms of Leishmania, an obligatory vertebrate intramacrophagic parasite, showing for the first time that unicellular organisms use apoptotic features for the establishment and/or maintenance of infection. Here we focus on PS exposure in the outer leaflet of the plasma membrane--an early hallmark of apoptosis--and how it modulates the inflammatory activity of phagocytic cells. We also discuss the possible mechanisms by which PS exposure can define Leishmania survival inside host cells and the evolutionary implications of apoptosis at the unicellular level.

Obstetric implications of low-lying placentas diagnosed in the second trimester

OBJECTIVES

To determine the obstetrical outcome of pregnancies initially complicated by a low-lying placenta in the second trimester.

METHODS

We reviewed the obstetric outcome of all women with singleton deliveries from 1 January 1997 to 31 March 1999 and compared the 703 women with low-lying placentas (placentas in the lower uterine segment) with the 6938 women with placentas that were normally situated in the upper uterine segment at 16-22 weeks' gestation.

RESULTS

Pregnancies complicated by a low-lying placenta in the second trimester were not associated with antepartum hemorrhage, preterm births, preterm prelabor rupture of membranes, pregnancy-induced hypertension, fetal growth restriction or cesarean births. However, they had a higher incidence of postpartum hemorrhage (odds ratio 1.768, 95% confidence interval 1.137, 2.748) than women with a normally situated placenta in the second trimester.

CONCLUSIONS

Pregnant women with low-lying placentas in the second trimester have a higher incidence of postpartum hemorrhage and hence, it would be prudent to carefully manage the third stage of labor in these women.

Lung cancer in pregnancy: case reports and review of the literature

Lung cancer diagnosed in pregnancy is rare. The number of reported cases has been escalating in recent years, probably reflecting the increasing number of women of reproductive age who smoke. This review presents three cases of lung cancer in pregnancy with different manifestations and outcomes, with a review of the literature. Physicians should have a low threshold using different diagnostic tools for investigating unusual symptoms during pregnancy without fear for fetal safety. Once diagnosed, lung cancer represents a major ethical and medical dilemma. The optimal management of lung cancer in pregnancy is not known, because of the rarity of the cases reported during pregnancy and insufficient follow-up data.

Outcome of pregnancy in women with hereditary thrombophilia

OBJECTIVES

The aims of this study are to review the outcome of pregnancy in women with thrombophilia, and investigate the possible beneficial effect of heparin therapy in these women.

METHODS

We reviewed the hospital records of 126 women who were referred to the high-risk obstetrical hematology clinic between June 1996 and December 1999. The placental histology and outcome of 39 pregnancies in 24 women with hereditary thrombophilia were studied, and pregnancies which were treated with heparin were compared with those without treatment.

RESULTS

An adverse pregnancy outcome occurred in 54% of the pregnancies. All seven miscarriages (18%) occurred in pregnancies that were not treated with heparin. However, heparin treatment did not prevent the development of obstetric complications in later pregnancies (odds ratio=0.955, 95% C.I.=0.255-3.577, Fisher's exact test). Excluding miscarriages, 28% of the placentas had thrombotic lesions, and the pregnancies with placental thrombotic lesions were more likely to have complications than those pregnancies without placental abnormalities (P=0.023, C.I.=1.257-5.197, Fisher's exact test).

CONCLUSIONS

Pregnancy complications in cases of hereditary thrombophilia may be related to placental abnormalities. Heparin therapy is likely to be useful in preventing miscarriage in cases of hereditary thrombophilia.

Socio-economic disparities in preterm birth: causal pathways and mechanisms

Preterm birth is the leading cause of infant mortality in industrialised societies. Its incidence is greatly increased among the socially disadvantaged, but the reasons for this excess are unclear and have been relatively unexplored. We hypothesise two distinct sets of causal pathways and mechanisms that may explain social disparities in preterm birth. The first set involves chronic and acute psychosocial stressors, psychological distress caused by those stressors, increased secretion of placental corticotropin releasing hormone (CRH), changes in sexual behaviours or enhanced susceptibility to bacterial vaginosis and chorioamnionitis, cigarette smoking or cocaine use, and decidual vasculopathy. The second hypothesised pathway is a gene-environment interaction based on a highly prevalent mutation in the gene for methylenetetrahydrofolate reductase (MTHFR), combined with low folate intake from the diet and from prenatal vitamin supplements, consequent hyperhomocysteinemia, and decidual vasculopathy. We propose to test these hypothesised pathways and mechanisms in a nested case-control study within a prospectively recruited and followed cohort of pregnant women with singleton pregnancies who deliver at one of four Montreal hospitals that serve an ethnically and socio-economically diverse population. Following recruitment during the late first or early second trimester, participating women are seen at 24-26 weeks, when a research nurse obtains a detailed medical and obstetric history; administers several scales to assess chronic and acute stressors and psychological function; obtains blood samples for CRH, red blood cell and plasma folate, homocysteine, and DNA for the MTHFR mutation; and performs a digital and speculum examination to measure cervical length and vaginal pH and to obtain swabs for bacterial vaginosis and fetal fibronectin. After delivery, each case (delivery at < 37 completed weeks following spontaneous onset of labour or prelabour rupture of membranes) and two controls are selected for placental pathological examination, hair analysis of cotinine, cocaine, and benzoylecgonine, and analysis of stored blood and vaginal specimens. Statistical analysis will be based on multiple logistic regression and structural equation modelling, with sequential construction of models of potential aetiological determinants and covariates to test the hypothesised causal pathways and mechanisms. The research we propose should improve understanding of the factors and processes that mediate social disparities in preterm birth. This improved understanding should help not only in developing strategies to reduce the disparities but also in suggesting preventive interventions applicable across the entire socio-economic spectrum.

Repeated neural tube defects and valproate monotherapy suggest a pharmacogenetic abnormality

Valproate (VPA) is an effective, widely used antiepileptic drug. Unfortunately its use in pregnant women is associated with neural tube defects in the offspring. Although the etiology of neural tube defects is multifactorial, there is evidence that underlying genetic susceptibility plays a part. We describe two women taking moderate doses of VPA who repeatedly bore children with neural tube defects, despite folate supplementation. This suggests a pharmacogenetic susceptibility to the teratogenic effects of VPA.

Obstetric admissions to the intensive care unit

OBJECTIVE

To determine whether obstetric admissions to the intensive care unit (ICU) are useful quality-assurance indicators.

METHODS

We analyzed retrospectively obstetric ICU admissions at two tertiary care centers from 1991 to 1997.

RESULTS

The 131 obstetric admissions represented 0.3% of all deliveries. The majority (78%) of women were admitted to the ICU postpartum. Obstetric hemorrhage (26%) and hypertension (21%) were the two most common reasons for admission. Together with cardiac disease, respiratory disorders, and infection, they accounted for more than 80% of all admissions. Preexisting medical conditions were present in 38% of all admissions. The median Acute Physiology and Chronic Health Evaluation II score was 8.5. The predicted mortality rate for the group was 10.0%, and the actual mortality rate was 2.3%.

CONCLUSION

The most common precipitants of ICU admission were obstetric hemorrhage and uncontrolled hypertension. Improved management strategies for these problems may significantly reduce major maternal morbidity.

Uveitis as the only clinical manifestation of poststreptococcal syndrome

PURPOSE

To report a case of streptococcal infection of the upper respiratory tract in which bilateral anterior uveitis was the only complication.

METHOD

Serologic documentation of post-streptococcal immune disease. The duration of inflammation was consistent with other forms of poststreptococcal immune disease.

RESULTS

Bilateral anterior uveitis was treated with corticosteroids alone and resolved without ophthalmic complications.

CONCLUSION

Bilateral anterior uveitis may be the only clinical manifestation of poststreptococcal syndrome.

The value of radiographs in the management of the fractured nose

Over a 6-month period a record was kept of all patients presenting to the accident and emergency (A&E) department with nasal injuries. The results of the nasal radiographs were analysed to gauge their benefit. It was found that there was poor correlation between the radiological findings and the presence of external deformity, the latter determining the decision to carry out treatment. Routine radiographs of the nose are unnecessary in patients with nasal trauma.

Caesarean section and phaeochromocytoma resection in a patient with Von Hippel Lindau disease

This report describes the anaesthetic management of a women with a term gestation, Von Hippel Lindau disease (VHLD), and a phaeochromocytoma, scheduled for a combined phaeochromocytoma resection and Caesarean section. Von Hippel Lindau disease is characterized by diffuse haemangioblastomas of the central nervous system (CNS) and viscera. It is also associated with phaeochromocytomas and renal cell carcinomas. Patients frequently have asymptomatic spinal cord and intracranial pathology. The patient and her fetus presented a challenge because of the anaesthetic restrictions imposed by VHLD, and her pregnancy. She was also at risk of developing malignant hypertension from the phaeochromocytoma. The patient was not a candidate for regional anaesthesia because of the possibility of spinal cord haemangioblastomas. She had received adrenergic blockade with phentolamine (total 30 mg a day) and propranolol (total 40 mg a day) since the 27th wk of gestation in order to control hypertension secondary to the phaeochromocytoma. General anaesthesia was administered with aggressive management of hypertension with adrenergic blockers (labetalol 1.0 mg.kg-1 and esmolol 0.75 mg.kg-1) and sodium nitroprusside 1.5 micrograms.kg-1 (total). Before delivery of the baby, opioids, which could have resulted in a fetus with CNS depression, were avoided. After delivery, opioids (sufentanil 0.4 microgram.kg-1 x hr-1) were used to limit the use of inhalational anaesthesia which may contribute to uterine atony. Postoperative pain was managed with an intravenous narcotic infusion. Both patients had uneventful postoperative courses.

DNA sequences and expression in Streptomyces lividans of an exoglucanase gene and an endoglucanase gene from Thermomonospora fusca

Two genes encoding cellulases E1 and E4 from Thermomonospora fusca have been cloned in Escherichia coli, and their DNA sequences have been determined. Both genes were introduced into Streptomyces lividans, and the enzymes were purified from the culture supernatants of transformants. E1 and E4 were expressed 18- and 4-fold higher, respectively, in S. lividans than in E. coli. Thin-layer chromatography of digestion products showed that E1 digests cellotriose, cellotetraose, and cellopentaose to cellobiose and a trace of glucose. E4 is poor at degrading cellotriose and cleaves cellopentaose to cellotetraose and glucose or cellotriose and cellobiose. It readily cleaves cellotetraose to cellobiose. E1 shows 59% identity to Cellulomonas fumi CenC in a 689-amino-acid overlap, and E4 shows 80% identity to the N terminus of C. fimi CenB in a 441-amino-acid overlap; all of these proteins are members of cellulase family E. Alignment of the amino acid sequences of Clostridium thermocellum celD, E1, E4, and four other members of family E demonstrates a clear relationship between their catalytic domains, although there is as little as 25% identity between some of them. Residues in celD that have been identified by site-directed mutagenesis and chemical modification to be important for catalytic activity are conserved in all seven proteins. The catalytic domains of E1 and E4 are not similar to those of T. fusca E2 or E5, but all four enzymes share similar cellulose-binding domains and have the same 14-bp inverted repeat upstream of their initiation codons. This sequence has been identified previously as the binding site for a protein that regulates induction.

Differential expression of retinal insulin receptors in STZ-induced diabetic rats

A major complication of diabetes mellitus is retinopathy, which is characterized by increased neovascularization and neuronal degeneration in the retina. The biochemical processes underlying these changes are largely unknown. To better understand the role(s) of insulin or its lack and the resultant hyperglycemia in the etiology of these events, peripheral and neuronal (having 125 kDa and 115 kDa alpha subunits, respectively) insulin receptor subtype levels in the retinas of Streptozocin-induced diabetic rats were quantified. Immunoblot analysis of wheat germ agglutinin-agarose purified retinal membrane proteins revealed that retinas from diabetic rats expressed higher insulin receptor levels than retinas from control rats. This increase reflected a doubling of neuronal and a approximately 20% decrease in peripheral insulin receptor subtypes, respectively. Insulin-treated diabetic rats had neuronal receptor levels equal to control values, at the same time having a further reduced number of peripheral insulin receptors relative to controls. Affinity labeling analysis of WGA-purified retinal membrane proteins indicated a 1.5-fold increase in neuronal and a 9% decrease in peripheral receptor subtypes, corroborating the immunoblot analysis. Neuronal insulin receptors in WGA-purified cortical synaptosomal membranes also were increased in diabetic rats, with insulin treatment reducing this effect. The up-regulated receptors retained their ability to undergo insulin-dependent autophosphorylation and, as such, did not appear functionally impaired. These data suggest that the expression of neuronal insulin receptors in retina and brain and peripheral insulin receptors in the retina of diabetic rats is sensitive to levels of insulin/glucose in peripheral circulation.

Characterization of a novel receptor in toad retina with dual specificity for insulin and insulin-like growth factor I

The biochemical properties of insulin receptors from toad retinal membranes were examined in an effort to gain insight into the role this receptor plays in the retina. Competition binding assays revealed that toad retinal membranes contained binding sites that displayed an equal affinity for insulin and insulin-like growth factor I (IGF-I). Affinity labeling of toad retinal membrane proteins with 125I-insulin resulted in the specific labeling of insulin receptor alpha-subunits of approximately 105 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of partially reduced (alpha beta-heterodimer) receptors affinity-labeled with 125I-insulin indicated the presence of a disulfide-linked beta-subunit of approximately 95 kDa. Endoglycosidase F digestion of the affinity-labeled alpha-subunits increased their mobility by reducing their apparent mass to approximately 83 kDa. This receptor was not detected by immunoblot analysis with a site-specific antipeptide antibody directed against residues 657-670 of the carboxy terminal of the human insulin receptor alpha-subunit, whereas this antibody did label insulin receptor alpha-subunits from pig, cow, rabbit, and chick retinas. In in vitro autophosphorylation assays insulin stimulated the tyrosine phosphorylation of toad retina insulin receptor beta-subunits. These data indicate that toad retinal insulin receptors have a heterotetrameric structure whose alpha-subunits are smaller than other previously reported neuronal insulin receptors. They further suggest that a single receptor may account for both the insulin and IGF-I binding activities associated with toad retinal membranes.

Identification of retinal insulin receptors using site-specific antibodies to a carboxyl-terminal peptide of the human insulin receptor alpha-subunit. Up-regulation of neuronal insulin receptors in diabetes

Insulin receptor-specific polyclonal antipeptide serum was generated against a synthetic pentadecapeptide (residues 657-670) of the deduced amino acid sequence of human insulin proreceptor cDNA for use in the analysis of insulin receptors in the retina. The affinity-purified antibodies recognized peptide antigen but not keyhole limpet hemocyanin as determined by dot blot analysis and solid phase radioimmunoassay. Addition of either synthetic peptide or the affinity-purified serum had no effect on 125I-insulin binding to placental membranes or to cells in culture. alpha-Subunits of approximately 125 kDa from human placental membranes and liver membranes were labeled by immunoblot analysis with this antiserum. In membranes isolated from human retina and brain, two classes of alpha-subunits of approximately 125 and 115 kDa were detectable. The 115-kDa subunit was neuraminidase resistant whereas the 125-kDa subunit was digested to a band of 115 kDa, indicating that these bands represent peripheral and neuronal receptors, respectively. Analysis of human retinas obtained from type I diabetic donors revealed an increased level of neuronal receptor as compared with normal retinas. These data indicate that human retina expresses neuronal insulin receptor subtypes that are up-regulated in diabetes.

Invasive monitoring and anaesthetic management of a parturient with mitral stenosis

The anaesthetic management of a parturient with mitral stenosis is presented and discussed. In particular, the beneficial effects of epidural anaesthesia for vaginal delivery are described with respect to the significant improvement noted in haemodynamic parameters. The information derived from the pulmonary artery catheter greatly assisted the management of the patient throughout labour and in the puerperium.

Has use of cesarean section reduced the risks of delivery in the preterm breech presentation?

The effect of cesarean section on the condition at birth in cases of preterm breech presentation was studied in consecutively delivered infants in two time periods. Delivery was rarely (8%) by cesarean section in 1961 to 1974 and usually (89%) by cesarean section in 1978 to 1984. The increased cesarean rate did not reduce the incidence of severe depression, which was double that in control cases with cephalic presentations in both periods. Breech births did not have a higher mortality rate than cephalic births in either period; birth trauma and encephalopathy were similar in both periods. Cesarean section was therefore not found to reduce either the incidence of depression at birth or the mortality. However, head entrapment was responsible for the deaths of seven of 55 live-born infants delivered vaginally at 25 to 28 weeks' gestation, all weighing less than 1000 gm. Although cesarean section is at present performed least often among these extremely premature infants, it is in these cases that it may prove most beneficial.