Time-Varying Network Models for the Temporal Dynamics of Depressive Symptomatology in Patients With Depressive Disorders: Secondary Analysis of Longitudinal Observational Data

BACKGROUND

As depression is highly heterogenous, an increasing number of studies investigate person-specific associations of depressive symptoms in longitudinal data. However, most studies in this area of research conceptualize symptom interrelations to be static and time invariant, which may lead to important temporal features of the disorder being missed.

OBJECTIVE

To reveal the dynamic nature of depression, we aimed to use a recently developed technique to investigate whether and how associations among depressive symptoms change over time.

METHODS

Using daily data (mean length 274, SD 82 d) of 20 participants with depression, we modeled idiographic associations among depressive symptoms, rumination, sleep, and quantity and quality of social contacts as dynamic networks using time-varying vector autoregressive models.

RESULTS

The resulting models showed marked interindividual and intraindividual differences. For some participants, associations among variables changed in the span of some weeks, whereas they stayed stable over months for others. Our results further indicated nonstationarity in all participants.

CONCLUSIONS

Idiographic symptom networks can provide insights into the temporal course of mental disorders and open new avenues of research for the study of the development and stability of psychopathological processes.

Neurons in the monoaminergic nuclei of the rat and human central nervous system express FA1/dlk

The gene DLK1 encodes a member of the epidermal growth factor (EGF) superfamily, delta-like (dlk). When exposed in vivo to the action of an unknown protease, this type 1 membrane protein generates a soluble peptide referred to as Fetal antigen 1 (FA1). By acting in juxtacrine as well as paracrine/autocrine manners, both forms have been shown to be active in the differentiation/proliferation process of various cell types. In adults, FA1/dlk has been demonstrated mainly within (neuro) endocrine tissues. In this study we investigated the presence of FA1/dlk in other parts of the developing and adult rat and human CNS. Using immunocytochemistry and in situ hybridization we found that in both species FA1/dlk was expressed in neurons of the Edinger-Westphal's nucleus as well as in substantia nigra, ventral tegmental area (VTA), locus coeruleus and in certain parts of the raphe nuclei.

Localization of lung surfactant protein D on mucosal surfaces in human tissues

Lung surfactant protein-D (SP-D), a collectin mainly produced by alveolar type II cells, initiates the effector mechanisms of innate immunity on binding to microbial carbohydrates. A panel of mRNAs from human tissues was screened for SP-D mRNA by RT-PCR. The lung was the main site of synthesis, but transcripts were readily amplified from trachea, brain, testis, salivary gland, heart, prostate gland, kidney, and pancreas. Minor sites of synthesis were uterus, small intestine, placenta, mammary gland, and stomach. The sequence of SP-D derived from parotid gland mRNA was identical with that of pulmonary SP-D. mAbs were raised against SP-D, and one was used to locate SP-D in cells and tissues by immunohistochemistry. SP-D immunoreactivity was found in alveolar type II cells, Clara cells, on and within alveolar macrophages, in epithelial cells of large and small ducts of the parotid gland, sweat glands, and lachrymal glands, in epithelial cells of the gall bladder and intrahepatic bile ducts, and in exocrine pancreatic ducts. SP-D was also present in epithelial cells of the skin, esophagus, small intestine, and urinary tract, as well as in the collecting ducts of the kidney. SP-D is generally present on mucosal surfaces and not restricted to a subset of cells in the lung. The localization and functions of SP-D indicate that this collectin is the counterpart in the innate immune system of IgA in the adaptive immune system.

Expression of proto-oncogenes in bovine preimplantation blastocysts

Proto-oncogenes are involved in the regulation of gene expression, for example after ligand binding to growth factor receptors. Expression of the proto-oncogenes c-fos, c-jun, c-ha-ras and c-myc was studied in in vivo grown and in vitro cultured bovine preimplantation blastocysts employing RT-PCR, ribonuclease protection assay and immunohistochemistry. Thirteen- and 14- day-old preimplantation blastocysts, i.e. stages before and during trophoblast elongation, were used. In in vivo-grown blastocysts c-fos, c-jun and c-ha-ras transcripts as well as c-Fos, c-Jun and c-Myc proteins were detected in all stages studied. Cultured blastocysts were treated with 10 nM epidermal growth factor and 10 nM transforming growth factor-alpha simultaneously. Epidermal growth factor and transforming growth factor-alpha treatment induced c-fos mRNA and c-Myc protein expression. The induction of downstream targets of the epidermal growth factor receptor by epidermal growth factor and transforming growth factor-alpha indicates a functional epidermal growth factor signal transduction pathway in elongating bovine blastocysts.

Fetal antigen 1, an EGF multidomain protein in the sex hormone-producing cells of the gonads and the microenvironment of germ cells

Fetal antigen 1 (FA1), an epidermal growth factor (EGF) multidomain glycoprotein, was investigated in the human reproductive system. Immunohistochemical analysis of the male reproductive system revealed staining for FA1 in the Leydig cells only. Concentrations of FA1 in seminal plasma and serum were similar and significantly correlated in weekly samples from three men (P < 0.0065). The concentrations in seminal plasma from vasectomized men (n = 4) were not significantly different from those of normal men (n = 187). The concentration of FA1 in seminal plasma was significantly correlated with the sperm counts of normozoospermic men (P < 0.0001), and significantly higher in seminal plasma from men with sperm counts > 20 x 10(6)/ml, compared with those with counts </= 20 x 10(6)/ml (P < 0. 0001). Immunohistochemical analysis of the ovary showed the presence of FA1 in the theca interna and the hilus cells but not in the granulosa cells or the oocyte. In follicular fluid the concentration of FA1 (median; 73.3 ng/ml, n = 28) was three times higher than that of serum (median; 23.8 ng/ml). These data suggest a role for this novel member of the EGF superfamily in relation to human reproduction, but further experiments are needed to define the biological function and to elucidate its clinical potential.

Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D

Surfactant protein D (SP-D) is an oligomeric C type lectin that promotes phagocytosis by binding to microbial surface carbohydrates. A 340-kDa glycoprotein (gp-340) has been shown to bind SP-D in the presence of calcium but does so independently of carbohydrate recognition. This protein exists both in a soluble form and in association with the membranes of alveolar macrophages. The primary structure of gp-340 has been established by molecular cloning, which yielded a 7,686-bp cDNA sequence encoding a polypeptide chain of 2, 413 amino acids. The domain organization features 13 scavenger receptor cysteine-rich (SRCR) domains, each separated by an SRCR-interspersed domain, except for SRCRs 4 and 5, which are contiguous. The 13 SRCR domains are followed by two C1r/C1s Uegf Bmp1 domains separated by a 14th SRCR domain and a zona pellucida domain. gp-340 seems to be an alternative spliced form of DMBT1. Reverse transcription-PCR analysis showed that the main sites of synthesis of gp-340 are lung, trachea, salivary gland, small intestine, and stomach. Immunohistochemistry revealed strong staining for gp-340 in alveolar and other tissue macrophages. Immunostaining of the macrophage membrane was either uniform or focal in a way that suggested capping, whereas other macrophages showed strong intracellular staining within the phagosome/phagolysosome compartments. In some macrophages, SP-D and gp-340 were located in the same cellular compartment. Immunoreactive gp-340 was also found in epithelial cells of the small intestine and in the ducts of salivary glands. The distribution of gp-340 in macrophages is compatible with a role as an opsonin receptor for SP-D.

Epidermal growth factor receptor and ligands in elongating bovine blastocysts

Preimplantation development depends on multiple interactions between mother and embryo. The Epidermal Growth Factor Receptor (EGF-R) and its ligands are potential components of the embryo-maternal cross-talk: Employing RT-PCR, in situ hybridization, and immunohistochemistry, we investigated on mRNA and protein level the expression of EGF-R, Epidermal Growth Factor (EGF), Transforming Growth Factor alpha (TGF-alpha), and Heparin-binding EGF-like Growth Factor (HB-EGF) in spherical and elongating bovine blastocysts between day 13 and day 16 of gestation, and in endometrium at day 13 of gestation. EGF-R mRNA and protein were detected in trophoblast and endoderm cells of all blastocyst stages that were studied, and in luminal and some glandular epithelial cells of the endometrium at day 13. EGF protein was detected in both blastocysts and endometrial epithelium. TGF-alpha transcripts and protein were present in blastocysts prior to and after elongation and in uterine glandular and luminal epithelium at day 13 of gestation. HB-EGF mRNA and protein was shown in the endoderm, and the protein also was detected immunohistochemically in about 45% of the blastocysts. This presence of the EGF receptor-ligand system in the endometrium and the preimplantation embryo at the time of blastocyst elongation suggests an important role for these growth factors during bovine preimplantation development.

Circulating concentrations of placenta protein 14 during the natural menstrual cycle in women significantly reflect endometrial receptivity to implantation and pregnancy during successive assisted reproduction cycles

Placenta protein 14 (PP14), which is the most abundant product of the secretory endometrium, has been proposed as the best biochemical marker of endometrial function in women. In this study, 19 normogonadotrophic women of infertile couples were monitored with serial measurements of concentrations of PP14, gonadotrophins and sex steroids and ultrasound scanning of endometrial thickness throughout three consecutive cycles. The first two of these were natural, unstimulated cycles (cycles 1 and 2), while ovarian stimulation with clomiphene and human menopausal gonadotrophin combined with assisted reproduction (intrauterine insemination in four cases and in-vitro fertilization in 15) was performed in the third cycle (cycle 3). A newly developed enzyme-linked immunosorbent assay was used to measure serum PP14 concentrations. In cycle 3, seven women became pregnant (group A) and 12 did not (group B). Circulating concentrations of PP14 were significantly lower in group A than in group B throughout all three cycles and in all cycle phases with exception of the late luteal phase of cycle 3, during which PP14 concentrations in group A were significantly higher than in group B. Statistical analyses showed no significant correlations between serum concentrations of PP14 and follicle stimulating hormone, luteinizing hormone and progesterone, and endometrial thickness. By contrast, serum oestradiol concentrations during the pre-ovulatory phase were significantly correlated with PP14 concentrations during the mid-luteal phase of the cycle. It is concluded that circulating PP14 is a most reliable biochemical marker of endometrial function in women and that relatively low concentrations in serum during the natural, unstimulated cycle are significantly correlated to implantation and pregnancy during successive assisted reproduction cycles. Measurement of PP14 in serum may thus be useful as a method of screening endometrial function in women, before commencing troublesome and costly treatment for infertility. However, further studies in a much larger number of women are needed to confirm this observation and to elucidate the as yet undefined physiological functions of PP14 in women.

Only a truncated epidermal growth factor receptor protein is present in porcine endometrium

The epidermal growth factor receptor (EGF-R) is a 170-kDa transmembrane protein, of which a truncated 100-kDa form (trEGF-R) lacking the cytoplasmic and the transmembrane domains, and an oncogenic 68-kDa form (v-erb) lacking the extracellular domain have been described. The trEGF-R is secreted and not able to transmit signals into the cell. Growth factors of the EGF family have been shown in porcine uterine fluids and blastocyst. Employing differential immunohistochemistry, we found the extracellular domain, but not the cytoplasmic domain, of the EGF-R in porcine endometrium on Days 9-11 of pregnancy. Blastocysts from Days 9 to 11 post coitum (p.c.) were positive for both antibodies, indicating the presence of the full-size receptor. Western Blotting of endometrial protein resulted in a 100-kDa band, but no 170-kDa band. No evidence for a coexpression of the 170- or 68-kDa forms of the receptor was found. ELISA analysis demonstrated trEGF-R in porcine uterine flushings. We conclude that 1) the trEGF-R is the only EGF-R form present in porcine endometrium, and 2) growth factors of the EGF family in porcine uterine fluids can exert their function via the EGF-R only on blastocysts, not on the endometrium.