Clinical characteristics and viral load dynamics of COVID-19 in a mildly or moderately symptomatic outpatient sample

Background

Studies of outpatients with mild or moderate COVID-19 are uncommon. We studied: 1) association of symptoms with reverse transcriptase polymerase chain reaction (RT-PCR) test results; and 2) association of initial RT-PCR cycle threshold (Ct) in relation to duration of RT-PCR positivity in outpatients with mild or moderate COVID-19.

Methods

This was a cohort study of outpatients with confirmed COVID-19 and at least one symptom. Participants had repeat nasopharyngeal swabs and symptom checklists every 3–5 days until two consecutive RT-PCR tests were negative. RT-PCR tests were used to assess viral load. Antibody tests for COVID-19 were performed at 2 weeks, 4 weeks, and 8 weeks after symptom onset.

Results

Twenty-five patients (nine females) were enrolled, ranging in age from 19–58 (median age 28 years). All patients reported at least one symptom, with a median of six symptoms per patient. Symptoms persisted for 6–67 days (median duration 18 days). In all 25 patients, blood samples collected a median of 13 days after symptom onset were positive for SARS-CoV-2 antibodies in 15 (60%). After a median of 28 days following symptom onset, 23/23 patients with available samples tested positive for antibodies. The longest duration of positive RT-PCR test was 49 days from first positive PCR test (Mean = 27.4, SD = 12.5, Median = 24). Initial Ct was significantly associated with longer duration (β = -1.3, SE = 0.3, p<0.01 per 1 cycle higher) of RT-PCR positivity.

Conclusions

In mildly or moderately ill COVID-19 outpatients, RT-PCT tests remained positive for as long as 49 days and test positivity and symptom duration correlated with initial viral load.

P–353 When Parents and Minor Children Disagree about Fertility Preservation: A Scoping Review and Ethical Analysis

Study question

Periodically, parents and children disagree about whether to pursue fertility preservation (FP). How should medical teams navigate these ethically complex situations?

Summary answer

Several considerations must be weighed, including the minor’s age, the burden of the proposed procedure, and whether the minor or parent seeks to decline FP.

What is known already

As reproductive technology advances, FP prior to gonadotoxic therapy has become the standard of care. Periodically, parents and children disagree about whether to pursue FP. To date, there is no clear guidance on how to navigate these difficult situations. Prior studies have demonstrated that adolescents undergoing gonadotoxic therapy want their views regarding FP to be taken into account, and also that most children and adolescents are comfortable with parental involvement in decision-making. However, transgender adolescents pursue FP at lower rates than adolescents with cancer, and more research is required to elucidate the unique needs and barriers of transgender youth.

Study design, size, duration

This study involves a scoping review and ethical analysis about parent-child disagreement regarding FP in minors. The review analyzes papers that either demonstrate that parent-child disagreement occurs, describe the preferences of parents or children regarding decision-making around FP, or provide recommendations that can be used to resolve parent-child conflicts. The ethical analysis weighs relevant rights and interests, including the child’s best interest, the right to an open future, the child’s autonomy, and parental autonomy.

Participants/materials, setting, methods

A search string was developed to identify all relevant published manuscripts on the topic of FP in minors, including studies on decision-making, family relations and ethical challenges. The search was run through several databases, abstracts were screened using Covidence, and data were extracted from full texts. Data abstracted from the review and existing literature on general medical decision-making for minors were used to construct an ethical framework for parent-child disagreements regarding FP in minors.

Main results and the role of chance

Published work directly on the topic of parent-child disputes regarding FP is limited, however a number of studies tangentially discuss parent-child disagreements and provide insight into the desires of parents and children regarding decision-making around FP. Studies suggest that adolescents desire to have their views taken into account, and a minority of adolescents believe their wishes alone should be followed. The age of the minor is a crucial factor, and some propose that as adolescents approach adulthood, their autonomy should increase. At the same time, in practice, legal and financial constraints often render parents the ultimate decision-makers. Our ethical analysis weighs competing considerations, including the child’s best interest, the right to an open future, the child’s autonomy, and parental autonomy. It concludes that who prevails should depend on contextual factors, including the minor’s age, the burden of the proposed procedure, and whether the minor or parent seeks to decline FP. There may also be special considerations for transgender adolescents, some of whom might have deeply personal reasons for pursuing or forgoing FP that are not well-understood by cisgender parents.

Limitations, reasons for caution

The scoping review captured a variety of results, including survey and interview studies, society guidelines, and ethical analyses. As such, we were unable to define a uniform quality metric. However, we aimed to be more rather than less inclusive because of the limited results directly pertaining to parent-child disagreements.

Wider implications of the findings: This study provides a robust review of decision-making for FP in minors and offers an ethical framework for weighing countervailing considerations when parents and children disagree about whether to pursue FP. The conclusions can be used to inform guidance for clinicians presented with this challenging ethical dilemma.

Trial registration number

N/A

P-353 When Parents and Minor Children Disagree about Fertility Preservation: A Scoping Review and Ethical Analysis

Study question

Periodically, parents and children disagree about whether to pursue fertility preservation (FP). How should medical teams navigate these ethically complex situations?

Summary answer

Several considerations must be weighed, including the minor’s age, the burden of the proposed procedure, and whether the minor or parent seeks to decline FP.

What is known already

As reproductive technology advances, FP prior to gonadotoxic therapy has become the standard of care. Periodically, parents and children disagree about whether to pursue FP. To date, there is no clear guidance on how to navigate these difficult situations. Prior studies have demonstrated that adolescents undergoing gonadotoxic therapy want their views regarding FP to be taken into account, and also that most children and adolescents are comfortable with parental involvement in decision-making. However, transgender adolescents pursue FP at lower rates than adolescents with cancer, and more research is required to elucidate the unique needs and barriers of transgender youth.

Study design, size, duration

This study involves a scoping review and ethical analysis about parent-child disagreement regarding FP in minors. The review analyzes papers that either demonstrate that parent-child disagreement occurs, describe the preferences of parents or children regarding decision-making around FP, or provide recommendations that can be used to resolve parent-child conflicts. The ethical analysis weighs relevant rights and interests, including the child’s best interest, the right to an open future, the child’s autonomy, and parental autonomy.

Participants/materials, setting, methods

A search string was developed to identify all relevant published manuscripts on the topic of FP in minors, including studies on decision-making, family relations and ethical challenges. The search was run through several databases, abstracts were screened using Covidence, and data were extracted from full texts. Data abstracted from the review and existing literature on general medical decision-making for minors were used to construct an ethical framework for parent-child disagreements regarding FP in minors.

Main results and the role of chance

Published work directly on the topic of parent-child disputes regarding FP is limited, however a number of studies tangentially discuss parent-child disagreements and provide insight into the desires of parents and children regarding decision-making around FP. Studies suggest that adolescents desire to have their views taken into account, and a minority of adolescents believe their wishes alone should be followed. The age of the minor is a crucial factor, and some propose that as adolescents approach adulthood, their autonomy should increase. At the same time, in practice, legal and financial constraints often render parents the ultimate decision-makers. Our ethical analysis weighs competing considerations, including the child’s best interest, the right to an open future, the child’s autonomy, and parental autonomy. It concludes that who prevails should depend on contextual factors, including the minor’s age, the burden of the proposed procedure, and whether the minor or parent seeks to decline FP. There may also be special considerations for transgender adolescents, some of whom might have deeply personal reasons for pursuing or forgoing FP that are not well-understood by cisgender parents.

Limitations, reasons for caution

The scoping review captured a variety of results, including survey and interview studies, society guidelines, and ethical analyses. As such, we were unable to define a uniform quality metric. However, we aimed to be more rather than less inclusive because of the limited results directly pertaining to parent-child disagreements.

Wider implications of the findings

This study provides a robust review of decision-making for FP in minors and offers an ethical framework for weighing countervailing considerations when parents and children disagree about whether to pursue FP. The conclusions can be used to inform guidance for clinicians presented with this challenging ethical dilemma.

Trial registration number

N/A

Whom Should We Test for COVID-19? Performance of a Symptom and Risk Factor Questionnaire on COVID-19 Test Results and Patient Outcomes in an Immediate Care Setting

Introduction:

The CDC and Illinois Department of Public Health disseminated risk factor criteria for COVID-19 testing early in the pandemic. The objective of this study is to assess the effectiveness of risk stratifying patients for COVID-19 testing and to identify which risk factors and which other clinical variables were associated with SARS-CoV-2 PCR test positivity.

Methods:

We conducted an observational cohort study on a sample of symptomatic patients evaluated at an immediate care setting. A risk assessment questionnaire was administered to every patient before clinician evaluation. High-risk patients received SARS-CoV-2 test and low-risk patients were evaluated by a clinician and selectively tested based on clinician judgment. Multivariate analyses tested whether risk factors and additional variables were associated with test positivity.

Results:

The adjusted odds ratio of testing positive was associated with COVID-19-positive or suspect close contact (aOR 1.56, 95% CI 1.15-2.10), large gathering attendance with a COVID-19-positive individual (aOR 1.92, 95% CI 1.10-3.34), and, with the largest effect size, decreased taste/smell (aOR 2.83, 95% CI 2.01-3.99). Testing positive was associated with ages 45-64 and ≥65 (aOR 1.75, 95% CI 1.25-2.44, and aOR 2.78, 95% CI 1.49-5.16), systolic blood pressures ≤120 (aOR 1.64, 95% CI 1.20-2.24), and, with the largest effect size, temperatures ≥99.0°F (aOR 3.06, 95% CI 2.23-4.20). The rate of positive SARS-CoV-2 test was similar between high-risk and low risk patients (225 [22.2%] vs 50 [19.8%]; P = .41).

Discussion:

The risk assessment questionnaire was not effective at stratifying patients for testing. Although individual risk factors were associated with SARS-CoV-2 test positivity, the low-risk group had similar positivity rates to the high-risk group. Our observations underscore the need for clinicians to develop clinical experience and share best practices and for systems and payors to support policies, funding, and resources to test all symptomatic patients.

Portrayal of Brain Death in Film and Television

We sought to evaluate whether television and cinematic coverage of brain death is educational or misleading. We identified 24 accessible productions that addressed brain death using the archives of the Paley Center for Media (160 000 titles) and the Internet Movie Database (3.7 million titles). Productions were reviewed by two board-certified neurologists. Although 19 characters were pronounced brain dead, no productions demonstrated a complete examination to assess for brain death (6 included an assessment for coma, 9 included an evaluation of at least 1 brainstem reflex, but none included an assessment of every brainstem reflex, and 2 included an apnea test). Subjectively, both authors believed only a small fraction of productions (13% A.L., 13% J.W.) provided the public a complete and accurate understanding of brain death. Organ donation was addressed in 17 productions (71%), but both reviewers felt that the discussions about organ donation were professional in a paucity of productions (9% for A.L., 27% for J.W.). Because television and movies serve as a key source for public education, the quality of productions that feature brain death must be improved.

Psychological impact of esophageal atresia: review of the research and clinical evidence

Esophageal atresia (EA) occurs in one out of 2500 to 4500 live births. As the vast majority of infants are now surviving neonatal corrective surgery, the focus has shifted from mortality to morbidity associated with EA. However, little is known about its psychological morbidity. This paper synthesizes research and clinical evidence to highlight the psychological sequelae of EA, including its impact on parents' psychological functioning and its effects on child development from infancy to adulthood. Whether it is discovered at birth or prenatally, EA is a psychologically traumatic event, and parents are at risk for developing traumatic stress reactions following diagnosis. Neonatal surgery and intensive care, risk of complications, associated anomalies, and genetic etiologies multiply risk for parents' acute and post-traumatic stress disorders (PTSD). Parental PTSD has a negative impact on infant and child development through its effects on parenting skills and parent-child interactions. EA children are also at risk for PTSD because of invasive and stressful procedures they undergo during the neonatal period. Consequences of EA can have an important long-term impact on children's psychological and social development. The scant studies pertaining to cognitive functioning suggest that EA does not affect mental development during infancy, but may be associated with deficits as children reach school age. Long-term sequelae are unclear because psychological functioning in adults has not yet been adequately examined. Research and clinical evidence of psychological morbidity associated with EA has implications for clinical practice. Psychological support for parents must begin during the neonatal period and should continue as an integral component of long-term follow up for both children and parents. Support is best provided within the context of a multidisciplinary treatment team that follows patients from birth through childhood and adolescence. Psychological follow up should continue into adulthood, as patients grow up and transition from pediatric to adult health-care settings.

Ethics of technologically constructed hypoxic environments in sport

With the use of technologically constructed hypoxic environments (TCHE) in soccer as our case, we propose four check points from which to evaluate new performance-enhancing technologies in sport. These are (I) Is the technology beneficial, (II) Is it safe, (III) Can fairness be assured, and (IV) Is the technology in line with the spirit of or rationale for sport? The use of TCHE is ambiguous. On the one hand, in situations with grave inequalities between teams due to lack of acclimatization of one team, TCHE can be an efficient means to even the playing field and out of concern for athlete welfare and health. On the other hand, if used as a pure performance-enhancing means to enhance the oxygen-carrying capacity of the blood independent of altitude, it belongs to a category of expert-assisted performance enhancement that may challenge athletic autonomy and the responsibility for one's own performance and, hence, the spirit of sport.

Do incentives matter? Providing benefits to families of organ donors

Whether the number of organs available for transplant would be positively or negatively affected by providing benefits to families of organ donors has been debated by policymakers, ethicists and the transplant community at large. We designed a telephone survey to measure public opinion regarding the use of benefits in general and of five types in particular: funeral benefits, charitable contributions, travel/lodging expenses, direct payments and medical expenses. Of the 971 adults who completed the survey (response rate = 69%), all were from Pennsylvania households, 45.6% were registered organ donors, and 51.7% were nonwhite. Although 59% of respondents favored the general idea of incentives, support for specific incentives ranged from 53% (direct payment) to 84% (medical expenses). Among those registered as donors, more nonwhites than whites supported funeral benefits (88% vs. 81%; p = 0.038), direct payment (63% vs. 41%; p < 0.001) and medical expenses (92% vs. 84%; p = 0.013). Among those not registered as donors, more nonwhites supported direct payment (64% vs. 46%; p = 0.001). Most respondents believed that benefits would not influence their own behavior concerning donation but would influence the behavior of others. While benefits appear to be favored, their true impact can only be assessed through pilot programs.

Porcine small intestine submucosa as a flexor tendon graft

An attractive strategy for tendon tissue engineering is the use of natural extracellular matrices as scaffold materials. One matrix that has been shown to promote healing and regeneration of neotissue in various applications is porcine-derived small intestinal submucosa. It was the objective of this study to investigate small intestinal submucosa for intrasynovial flexor tendon grafting in a canine model. We hypothesized that at 6 weeks small intestinal submucosa grafts would undergo host cell infiltration, neovascularization, and replacement by host neotendon. We also hypothesized that small intestinal submucosa grafts would be incorporated by the host without extensive adhesions to surrounding tissues and therefore maintain normal digit function. An intrasynovial tendon autograft was used as a gold standard. At 6 weeks the intrasynovial tendon autografts remained viable, contained normal numbers of cells along their length, and had minimal peritendinous adhesions. Four of six autografts had normal function as determined by rotation of the distal interphalangeal joint. Also at 6 weeks, the small intestinal submucosa grafts had host cell infiltration, neovascularization, and wavy, oriented tissue. However, ubiquitous adhesions together with impaired function in all cases suggest that small intestinal submucosa grafts in the configuration used are not suitable as full-length intrasynovial grafts in this tendon and animal model.

The Pain Relief Promotion Act of 1999: a serious threat to palliative care

Recent educational efforts in the US medical community have begun to address the critical issue of palliative care for terminally ill patients. However, a newly introduced bill in Congress, the Pain Relief Promotion Act of 1999 (PRPA), could dramatically hinder these efforts if enacted. The act criminally punishes the use of controlled substances to cause-or assist in causing-a patient's death. The primary purposes of PRPA are to override the physician-assisted suicide law currently in effect in Oregon and prohibit other states from enacting similar laws. The act also includes valuable provisions for better research and education in palliative care, but the benefits of those provisions are outweighed by the punitive sections of the act. Under PRPA, the quality of palliative care in the United States could be compromised when physicians, fearing criminal prosecution, err on the side of caution rather than risk their patients' deaths by using highly aggressive pain treatments. Furthermore, PRPA would put Drug Enforcement Administration officials, who have no medical expertise, in the position of regulating medical decisions. The act also would interfere with individual states' long-standing authority over medical practice. Finally, PRPA would discourage physicians from engaging in experimentation and innovation in palliative care, again out of concern for crossing the line between relief of suffering and physician-assisted suicide. Other bills have been introduced that go much further than PRPA to encourage palliative care, without its problematic provisions. Regardless of the controversy surrounding physician-assisted suicide in the United States, the need for quality end-of-life care will be far better served if Congress enacts one of these bills rather than PRPA.

Stem cell politics, ethics and medical progress

Tremendous controversy has surrounded efforts to undertake research on totipotent human stem cells. To date public policy in the United States has attempted to skirt the ethical and social questions raised by this research. Annas et al. argue that research using human embryos as a source of totipotent stem cells can secure broad public support if there is an open and public discussion about the ethical justification for undertaking such research and the assurance of adequate federal regulation and oversight.

The expression of the salt-responsive gene salT from rice is regulated by hormonal and developmental cues

The expression pattern of the salT gene was analyzed in different cell types and organs of rice (Oryza sativa L.) in response to saline and hormonal treatments to obtain detailed information on the physiological cues controlling gene expression. Gel blot analysis of RNA and in-situ hybridization performed on seedlings grown for 10 ds in the presence of 1% NaCl revealed that salT was expressed mainly in the younger tissues of the plant. In contrast, 6-week-old plants exhibited maximal salT mRNA accumulation in sheaths of older leaves. In addition, salT was normally expressed in rapidly dividing suspension-cultured cells, but not in quiescent ones. Altogether, these results may indicate that salT expression in each region of the plant is dependent on the metabolic activity of the cells as well as on whether or not they are stressed. The effects of two growth regulators, abscisic acid (ABA) and gibberellic acid, were investigated in combination with the effects of NaCl. Gibberellic acid had a synergistic effect on the induction of the salT gene when combined with 0.5% NaCl, but did not induce salT on its own. At 10 microM, ABA induced salT both in the absence of NaCl and in its presence. Whereas 1 microM ABA acted additively with NaCl to induce gene expression, 5 microM ABA with NaCl was only as effective as NaCl alone. This may indicate that the two stimuli act independently and possibly through antagonistic signal transduction pathways.

Paradigms for clinical ethics consultation practice

Clinical bioethics is big business. There are now hundreds of people who “do” bioethics in community and university hospitals, nursing homes, rehabilitation and home care settings, and some (though quite a few less) who play the role of clinical ethics consultant to transplant teams, managed care companies, and genetic testing firms. Still, there is as much speculation about what clinically active bioethicists actually do as there was ten years ago. Various commentators have pondered the need for training standards, credentials, “certification” exams, and malpractice insurance for ethicists engaged in clinical consultation. Much of the discussion seems to accept an implicit presumption that all clinical ethics consultation practices look pretty much alike. But is this accurate? What do clinical ethicists do, how and where do they do it, and what kind of clinical ethics is useful in the hospital and in other settings?

Phenotypic characterization of a tobacco mutant impaired in auxin polar transport

A mutation in tobacco (Nicotiana tabacum L. cv `Xanthi') called lat (low auxin transport) that changes many morphogenic features throughout the life of the plant has been isolated. Abnormalities were observed in seed development, embryogenesis, cotyledon formation, leaf initiation and development, leaf veination pattern, and flower development. Selfed R₂ lat mutant plants set between 60% and 90% fewer seeds than wild-type tobacco, and about 10% of these seeds did not germinate. Non-germinating seeds contained either abnormal embryos or abnormal endosperm tissues. There was no uniformity in the stage at which embryonic development ceased in the aberrant seeds. Seedlings often revealed abnormal and highly varied phenotypes after germination. In some of these cases, cotyledons were heart-shaped, fused, cup-shaped, or cylindrical. Leaf morphology ranged from normal to cup-shaped, and some leaves occasionally produced shoots from the leaf midvein. Flowers ranged from normal to compound with occasional fused floral parts or split petals. Stamens were sometimes petal-like. This unusual assortment of phenotypic changes suggested that the mutation might affect a basic component of plant metabolism. We found that polar transport of indole-3-acetic acid (IAA) was reduced to about 9-19% of the wild-type level in the inflorescence axis of selfed R₂ lat mutants. In addition, supplementation of 1-naphthaleneacetic acid (NAA) to sterile media suppressed some of the abnormalities of the lat mutation so long as the plants grew there. Similarities in the phenotype of embryos, cotyledon and leaf shapes, translocation of labeled IAA, and response to applied NAA indicate that the lat locus of tobacco may be analogous to the pin locus of Arabidopsis, or produce a protein that functions in the same auxin-transport pathway.

Postmortem sperm procurement

PURPOSE

We determined the prevalence of requests for postmortem sperm procurement and the degree to which procurement is performed by those working in the field of infertility.

MATERIALS AND METHODS

Structured telephone interviews were conducted with personnel at 273 assisted reproductive facilities in the United States and Canada. The number of facilities reporting requests and the number of facilities reporting that they performed the procedure were determined.

RESULTS

The prevalence of requests for postmortem sperm procurement was much greater than initially anticipated. A total of 82 requests was reported at 40 facilities in 22 different states between 1980 and 1995. More than half of the reported requests (43) were made between 1994 and 1995. Of the 82 requests 25 were honored at 14 facilities in 11 different states. No requests or procedures were reported from Canada.

CONCLUSIONS

Medical advances in postmortem sperm procurement, cryopreservation and in vitro fertilization permit retrieval of sperm after death for various purposes, including posthumous fatherhood. There are no explicit ethical guidelines, legislation or relevant case law, and fertility specialists must confront these issues before proceeding in a field fraught with moral and policy uncertainties.

Differential Accumulation of Salicylic Acid and Salicylic Acid-Sensitive Catalase in Different Rice Tissues

We previously proposed that salicylic acid (SA)-sensitive catalases serve as biological targets of SA in plant defense responses. To further examine the role of SA-sensitive catalases, we have analyzed the relationship between SA levels and SA sensitivity of catalases in different rice (Oryza sativa) tissues. We show here that, whereas rice shoots contain extremely high levels of free SA, as previously reported (I. Raskin, H. Skubatz, W. Tang, B.J.D. Meeuse [1990] Ann Bot 66: 369-373; P. Silverman, M. Seskar, D. Kanter, P. Schweizer, J.-P. Metraux, I. Raskin [1995] Plant Physiol 108: 633-639), rice roots and cell-suspension cultures have very low SA levels. Catalases from different rice tissues also exhibit differences in sensitivity to SA. Catalase from rice shoots is insensitive to SA, but roots and cell-suspension cultures contain SA-sensitive catalase. The difference in SA sensitivity of catalases from these different tissues correlates with the tissue-specific expression of two catalase genes, CatA and CatB, which encode highly distinctive catalase proteins. CatA, which encodes a catalase with relatively low sequence homology to the tobacco SA-sensitive catalases, is expressed at high levels exclusively in the shoots. On the other hand, in roots and cell-suspension cultures, with northern analysis we detected expression of only the CatB gene, which encodes a catalase with higher sequence homology to tobacco catalases. The role of catalases in mediating some of the SA-induced responses is discussed in light of these results and the recently defined mechanisms of catalase inhibition by SA.

Conductivity detection in capillary electrophoresis--a powerful tool in ion analysis

Conductivity detection in CE has recently become available in a commercial CE instrument. The new conductivity cell is based on an end-capillary concept. The conductivity sensor and the detection end of the fused-silica capillary are permanently encapsulated in two individually modified coupling connectors (ConTip, ConCap [both from Orion Research, Boston, MA, U.S.A.]). This open-architecture cell permits interchangeability of sensors and capillaries, while maintaining a precisely defined detection volume between those two components when inserted into the detector cell block. The detector's performance is evaluated for sensitivity, linearity, and reproducibility using low-mobility electrolytes. Electropherograms comprising a variety of ionic class separations including inorganic and organic anions, organic surfactants, alkali metals, alkaline earths, transition metals, and organic amines are shown along with separations of actual samples.

A group of chromosomal proteins is specifically released by spermine and loses DNA-binding activity upon phosphorylation

Biologically relevant concentrations as low as 500 microM spermine led to the specific release of chromatin-associated proteins from nuclei of rice (Oryza sativa) seedlings. Using a southwestern technique, it was shown that several of these proteins bind DNA. This affinity was lost upon in organello phosphorylation by an endogenous kinase. The effect of spermine was very specific. Spermidine was far less effective and putrescine was essentially ineffective in releasing these proteins. The most abundant spermine-released protein was shown to be homologous to the maize HMG1 protein. Our results suggest that spermine induces the release of spermine-released proteins by changing DNA conformation. Binding of these proteins might be sensitive to long-range changes in chromosome structure caused by torsional stress.

Immunoglobulin G binding sites on the human foetal intestine: a possible mechanism for the passive transfer of immunity from mother to infant

In humans, the prenatal transfer of IgG from mother to foetus is facilitated by a receptor for IgG on the placenta. However, amniotic fluid contains IgG of maternal origin, and transfer of swallowed IgG into the circulation from the foetal intestine represents another potential pathway of passive immunization. In this study we assayed for a foetal intestinal IgG receptor to support the hypothesis of this alternate pathway of antibody transfer. Microvillous membrane (MVM) from small bowel of aborted foetuses (18 weeks gestation) were probed with [125I]IgG to detect specific IgG binding sites. Binding was pH dependent and was maximal at pH 6. Competitive inhibition of the binding of [125I]IgG was noted with the addition of increasing amounts of unlabelled IgG. Scatchard analysis showed one binding site with a dissociation constant of 1.58 x 10(-7), similar to that of the IgG receptor described on the suckling rat intestine. The binding of labelled IgG to the human MVM receptor was Fc mediated. These observations provide evidence for an Fc receptor on the human foetal intestine.