Demographic and endocrinological aspects of low natural fertility in Highland New Guinea

The Gainj of highland Papua New Guinea do not use contraception but have a total fertility rate of only 4·3 live births per woman, one of the lowest ever recorded in a natural fertility setting. From an analysis of cross-sectional demographic and endocrinological data, the causes of low reproductive output have been identified in women of this population as: late menarche and marriage, a long interval between marriage and first birth, a high probability of widowhood at later reproductive ages, low effective fecundability and prolonged lactational amenorrhoea. These are combined with near-universal marriage, a low prevalence of primary sterility and a pattern of onset of secondary sterility similar to that found in other populations. Of all the factors limiting fertility, by far the most important are those involved in birth spacing, especially lactational amenorrhoea.

Lactation and birth spacing in highland New Guinea

The effects of infant suckling patterns on the post-partum resumption of ovulation and on birth-spacing are investigated among the Gainj of highland New Guinea. Based on hormonal evidence, the median duration of lactational anovulation is 20·4 months, accounting for about 75% of the median interval between live birth and next successful conception (i.e. resulting in live birth). Throughout lactation, suckling episodes are short and frequent, the interval changing slowly over time, from 24 minutes in newborns to 80 minutes in 3-year olds. Maternal serum prolactin concentrations decline in parallel with the changes in suckling patterns, approaching the level observed in non-nursing women by about 24 months post-partum. A path analysis indicates that the interval between suckling episodes is the principal determinant of maternal prolactin concentration, with time since parturition affecting prolactin secretion only in so far as it affects suckling frequency. The extremely prolonged contraceptive effect of breast-feeding in this population thus appears to be due to (i) a slow decline in suckling frequency with time since parturition and (ii) absence of a decline over time in hypothalamic–pituitary responsiveness to the suckling stimulus.

Application of the enzyme-linked immunosorbent assay for the detection of platelet antibodies in dogs

An enzyme-linked immunosorbent assay (ELISA) was developed to detect serum antibodies reactive to canine platelets. The method used an anti-canine immunoglobulin G horseradish peroxidase conjugate, O-dianisidine, as a water-soluble chromagen, and pooled platelets as a temporary antibody support. The ELISA was compared with a conventional immunoinjury method measuring the accelerating effect of platelet factor 3 on coagulation. The ELISA was more sensitive in the detection of antiplatelet antibodies in canine patients with idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia, and systemic lupus erythematosus. Serial dilution of rabbit anti-canine platelet serum revealed a positive correlation between the strength of the antiserum and the degree of color measured spectophotometrically, indicating that the absorbance value may be useful in estimating the amount of antibody present in the serum in indirect tests and on the platelets in direct tests.

Application of the enzyme-linked immunosorbent assay to detect canine erythrocyte antibodies

A double-antibody enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies bound to canine RBC. The method used a horseradish peroxidase conjugate, o-dianisidine, as a water-soluble chromogen and osmotically lysed RBC on which antibody was detected. The ELISA method was compared with the traditional antiglobulin (Coombs') test on positive controls, using sheep RBC sensitized with dilutions of canine anti-sheep RBC serum and on RBC from canine patients tested for autoantibodies to RBC. The ELISA method appeared to be more sensitive than the Coombs' test and gave an estimate of the amount of antibody present without the need for serial antiserum dilutions to determine the antibody titer.

Hepatitis in a dog given sulfadiazine-trimethoprim and cyclophosphamide

Vomiting, diarrhea, icterus and elevated serum alkaline phosphatase, SGPT and serum bilirubin levels occurred in a 12-year-old Basenji on sulfadiazine-trimethoprim and cyclophosphamide therapy. After use of the antibacterial drug was discontinued, the dog returned to normal with no further evidence of hepatocellular damage.

Differential processing of the two subunits of human choriogonadotropin by granulosa cells. II. In vivo studies

Using a well characterized preparation of hCG, consisting of a mixture of hCG labeled in the alpha-subunit with 125I and hCG labeled in the beta-subunit with 131I (see preceding paper), the hormone-specific preferential retention by granulosa cells in vivo of the radiolabel originally associated with the beta-subunit of hCG has been confirmed and extended. Additional studies have shown that this retention is peculiar to the granulosa cells. Luteal and interstitial/thecal elements of the ovary failed to show preferential accumulation of the label originally associated with the beta-subunit. Measurement of both radioactivities in crude subfractions of the ovarian tissues revealed that granulosa cells retain the excess of beta-subunit label in a plasma membrane/vesicular component. No such preferential retention of label was seen in any of the subfractions obtained from luteal or interstitial/thecal tissues. The radiolabeled components associated with the granulosa cells were shown to be mainly macromolecular by their precipitability with 13% trichloroacetic acid. Luteal tissue degraded the components associated with each label more rapidly than granulosa cells. In contrast, interstitial/thecal tissue degraded very little of the bound labeled components. The differential processing of individual hCG subunits by granulosa cells was shown not to result from different kinetics of binding of serum-borne hormone by two methods. Thus, changes over time in the ability of circulating hormone to bind to LH receptor in vitro were shown not to be a function of the hCG subunit having the label. Moreover, blockade of further radiolabel uptake by injection of a large excess of unlabeled hCG 30 min after radiolabel administration did not alter the rise in the ratio of beta-subunit label to alpha-subunit label normally observed in granulosa cells. The ability of kidney tissue to accumulate and metabolize hCG also varied with the physiological state. Within the limitations of following the radioiodides added to proteins rather than the peptides themselves, these studies demonstrate that differences exist in the metabolism of hCG by the various target cells of the ovary and that changes in processing occur during luteinization.

Differential processing of the two subunits of human choriogonadotropin (hCG) by granulosa cells. I. Preparation and characterization of selectively labeled hCG

The alpha- and beta-subunits of hCG were radioiodinated and recombined with unlabeled complementary subunits. The resultant recombined hormones, selectively labeled in either the alpha- or beta-subunit, were separated from unrecombined subunit by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, extracted with Triton X-100, and characterized by binding analysis. The estimates of maximum binding (active fraction) of the two resultant selectively labeled, recombined hCG preparations, determined with excess receptor were 0.41 and 0.59. These values are similar to those obtained when hCG is labeled as an intact molecule. The specific activities of the recombined preparations were estimated by four different methods, and the resulting values were used in combination with the active fraction estimates to determine the concentrations of active free and bound hormone. Binding analyses were run using varying concentrations of both labeled and unlabeled hormone. Estimates of the equilibrium dissociation binding constant (Kd) and receptor capacity were calculated in three different ways. The mean estimates of capacity (52.6 and 52.7 fmol/mg tissue) and Kd (66.6 and 65.7 pM) for the two preparations were indistinguishable. Additionally, these values were similar to values reported previously for hCG radioiodinated as an intact molecule. The availability of well characterized, selectively labeled hCG preparations provides new tools for studying the mechanism of action and the target cell processing of the subunits of this hormone.

Differential processing of subunits of human chorionic gonadotropin by granulosa cells in vivo

The question of whether the two subunits of the glycoprotein hormone human chorionic gonadotropin (hCG) are handled separately or as a unit by target cells was addressed by using a dual-labeling procedure. The individual alpha and beta subunits of hCG were labeled with 131I or 125I, recombined, chromatographed, and injected intravenously into hormonally primed immature rats. The ovaries of these rats contained large numbers of antral follicles, the granulosa cells of which possess high concentrations of receptor for hCG. Comparisons of the distribution of the different radioisotopic labels in various tissues over time indicated the activity associated with the beta subunit was preferentially retained by the ovarian granulosa cells in a hormone-specific manner, while the activity associated with the alpha subunit was preferentially lost. This contrasted with other tissues, including other ovarian cells with receptor for hCG, in which both radiolabels were either handled nondifferentially or handled differentially in a hormonally nonspecific manner.

Rapid changes in the synthesis of specific ovarian granulosa cell proteins induced by human choriogonadotropin

Total ovarian granulosa cell proteins were labeled in vitro with [35S]methionine and analyzed by two-dimensional polyacrylamide gel electrophoresis. Of the 100-150 distinct proteins resolved by this method, 1-2% demonstrated an observable change in their synthesis during the early phases of luteinization after hormone administration. Two specific proteins first appeared as early as 30 min after treatment with human choriogonadotropin, while four additional new proteins became apparent at 3 hr. These changes in the synthesis of specific proteins occurred far in advance of the morphological changes associated with luteinization, which occur 24-72 hr later, and thus may play an important role in this process of hormonally induced cell differentiation in the rat ovary.