From decimeter-scale elevated ionic conductivity regions in the cloud to lightning initiation.

In this work, we represent the lightning initiation scenario as a sequence of two transitions of discharge activity to progressively larger spatial scales: the first one is from small-scale avalanches to intermediate-scale streamers; and the second one is from streamers to the lightning seed. We postulate the existence of ion production centers in the cloud, whose occurrence is caused by electric field bursts accompanying hydrometeor collisions (or near collisions) in the turbulent thundercloud environment. When a new ion production center is created inside (fully or partially) the residual ion spot left behind by a previously established center, there is a cumulative effect in the increasing of ion concentration. As a result, the essentially non-conducting thundercloud becomes seeded by elevated ion-conductivity regions (EICRs) with spatial extent of 0.1-1 m and a lifetime of 1-10 s. The electric field on the surface of an EICR (due to its conductivity being at least 4 orders of magnitude higher than ambient) is a factor of 3 or more higher than ambient. For a maximum ambient electric field of 100 kV/m typically measured in thunderclouds, such field enhancement is sufficient for initiation of positive streamers and their propagation over distances of the order of decimeters, and this will be happening naturally, without any external agents (e.g., superenergetic cosmic ray particles) or extraordinary in-cloud conditions, such as very high potential differences or very large hydrometeors. Provided that each EICR generates at least one streamer during its lifetime, the streamers will form a 3D network, some parts of which will contain hot channel segments created via the cumulative heating and/or thermal-ionizational instability. These hot channel segments will polarize, interact with each other, and cluster, forming longer conducting structures in the cloud. When the ambient potential difference bridged by such a conducting structure exceeds 3 MV, we assume that the lightning seed, capable of self-sustained bidirectional extension, is formed.

Compound heterozygous deletion of the PROP-1 gene in children with combined pituitary hormone deficiency.

Mutations in the prophet of Pit-1 gene (PROP1) have been shown to be responsible for combined pituitary hormone deficiency (CPHD) with deficiencies of growth hormone (GH), Prolactin (Prl), thyroid-stimulating hormone (TSH) and gonadotropins. We previously reported that homozygosity for a 2bp deletion in exon 2 (296delGA) accounted for CPHD in three patients from two Russian families. Here we report a second mutational hot spot in exon 2. This 2bp 149delGA deletion results in a frame shift that leads to the same serine to stop codon change at codon 109 (S109X). The predicted proteins are each truncated at residue 108 but diverge from the wild type sequence at different points in the homeodomain. Compound heterozygosity for the two mutations (149delGA/296delGA) was detected in 5 of 14 CPHD children from 4 families (36%). This provides the first evidence of heterozygosity for two common deletions as a cause of CPHD in Russian children.

A mutational hot spot in the Prop-1 gene in Russian children with combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD), including growth hormone (GH), prolactin (Prl) and thyroid-stimulating hormone (TSH) in children is now considered a heterogeneous syndrome. Recent findings on expression of mouse pituitary-specific homeodomain factors demonstrate dependence of adenopituitary ontogeny on interactive expression of these factors, suggesting their involvement in etiology of CPHD. Prophet of Pit-1 (Prop-1) gene, a novel pituitary-specific homeodomain factor, was analyzed in 14 Russian children with CPHD, in whom Pit-1 gene was intact. We found a mutational hot spot in three patients from two families in homeodomain part of the second exon of Prop-1 gene. The common 2-base pair deletion (GA296) in the homozygous state resulted in a Serine to Stop codon (S109X) substitution and generated a truncated Prop-1 protein. Parents were phenotypically normal and heterozygous for GA296 deletion, indicating an autosomal recessive inheritance. These results demonstrate a novel type of Prop-1 gene mutation as one of the causes of CPHD in Russian patients.

Biochemical nature of high-molecular-weight prolactin of human serum: identification of a prolactin-binding protein.

The biochemical nature of a high-molecular-weight immunoreactive prolactin (HMW-irPRL) prepared by gel filtration of women's sera with predominance of this hormone form was studied. Immunochemical characteristics of HMW-irPRL are different from those of 23 kD prolactin (23 kD-PRL). A protein which specifically and reversibly binds to human [125I]PRL is isolated from the pooled fractions of HMW-irPRL by affinity chromatography on prolactin-Sepharose. According to gel filtration, the binding protein (BP) has molecular weight about 150 kD, and it reversibly binds to protein A immobilized on Sepharose. Analysis of BP by SDS-PAGE resulted in two major protein bands, of 65-70 and approximately 150 kD. Both the bands, when transferred to nitrocellulose, interacted with [125I]protein A. Binding of highly purified human pituitary prolactin to the BP significantly decreased the immunoreactivity of the hormone. The molecular weight of BP and its interaction with protein A and recognition by poly- and monoclonal antibodies against human (but not guinea pig) IgG indicate that BP may be an immunoglobulin. Thus, our data demonstrate that HMW-irPRL is formed by the binding of 23 kD-PRL to a specific serum protein which is probably an anti-prolactin IgG.

[Comparison of biological activity of high molecular weight and low molecular weight forms of immunoreactive prolactin from human serum in cultured lymphoma NB2 cells]. / Sravnenie biologicheskoi aktivnosti vysokomolekuliarnoi i nizkomolekuliarnoi form immunoreaktivnogo prolaktina syvorotki krovi cheloveka v kul'ture kletok NB2 limfomy.

In experiments with NB2 rat lymphoma cells culture sensitive to lactogenic hormones the mitogenic activity of high molecular weight (> OOK) immunoreactive prolactin, found in substantial quantities in serum of certain hyperprolactinemic women, as compared to the activity of serum low molecular weight (23K) form, was studied. It was established that the ratio of immunoreactive to biologically active prolactin content in serums in cases of low molecular weight form predominance is close to 1,0 whereas in case of predominant content of high molecular weight form it is substantially higher (1.5-2.3), apparently because of low biological activity of high molecular weight form. Direct comparison of mitogenic effects of equivalent quantities of serum immunoreactive prolactin forms with high and low molecular weight, separated by gel-filtration, confirmed low biological activity of high molecular weight form. Monoclonal antibodies to prolactin completely suppressed mitogenic activity of low molecular weight form and only partially--high molecular weight one. The data obtained indicate that high and low molecular weight forms of human serum immunoreactive prolactin differ in their biochemical and functional characteristics. Therefore their ratio in the circulating blood can substantially affect the clinical manifestations of hyperprolactinemia.

[Molecular forms of human growth hormone and prolactin, secreted by cultured pituitary tumor cells]. / Molekuliarnye formy gormona rosta i prolaktina cheloveka, sekretiruemye kul'turami kletok opukholei gipofiza.

Functionally active cultures of human pituitary adenoma cells producing excessive amounts of the growth hormone (somatotropinomas), of prolactin (prolactinomas) or of the both hormones (mixed type adenomas) have been prepared and their secreted molecular forms studied. SDS-PAAG electrophoresis combined with immunoblotting making use of poly- and monoclonal antibodies revealed that the growth hormone and prolactin are secreted by adenoma cells in several molecular forms typical of normal human pituitary. The major form secreted by the growth hormone is 22K; the minor forms are 20K (the product of alternative splicing of pre-mRNA) and the split-off two-chain form 25K. The major form secreted by prolactin is 23K; the minor form is glycosylated 25K. No significant differences in the ratios of molecular forms of the hormones were found either under basal conditions of culturing or under the influence of the pituitary function regulators, somatostatin and thyroliberin. At the same time, the data obtained suggest that pituitary adenoma cells can secrete some amount of "abnormal" molecular forms of the hormones, e.g., immature products of postribosomal processing or large-sized immunoreactive fragments. Hence, pituitary adenoma cell cultures are an effective tool in biochemical and physiological studies of molecular forms of the human growth hormone and prolactin and of their secretion.

[The alpha subunit of glycoprotein hormones as a biochemical marker of pituitary tumors]. / Al'fa-sub''edinitsa glikoproteinovykh gormonov kak biokhimicheskii marker opukholei gipofiza.

Specific radioimmunoassay was developed for detection free glycoprotein hormone alpha-subunit (AS), by using AS prepared from highly purified human thyroid-stimulating hormone (TSH). The assay showed that the basal content of free serum AS in the majority of 24 females with hormonally pituitary tumors secreting somatotropic hormone (STH, growth hormone), prolactin or either and in 24 females with unfunctioning pituitary tumors was significantly higher the mean one in 12 females matched for the same age who had no endocrine diseases (control). The cultured cells of STH- and P-secreting tumors released excessive quantities of free AS along with STH and P into the medium with low glycoprotein holo-hormone levels. The content of AS changed little in 12 patients with non-functioning pituitary tumors despite the greatly increased serum TSH levels in response to the hypothalamic stimulator thyroid-releasing hormone. The findings suggest that free AS secreted into blood in excess despite hypothalamic control may be regarded as a biochemical marker of pituitary tumors.

Growth hormone (GH)-releasing effects of synthetic peptide GH-releasing peptide-2 and GH-releasing hormone (1-29NH2) in children with GH insufficiency and idiopathic short stature.

To investigate how growth hormone (GH)-releasing peptide (GHRP) and GH-releasing hormone (GHRH) interact in patients with short stature, we examined the acute effects of GHRH1-29NH2, GHRP-2, and the combination of GHRH1-29NH2 and GHRP-2 on GH release in children with GH insufficiency ([GHI] group A) and idiopathic short stature ([ISS] group B). Ten children with GHI (aged 11.8 +/- 1.1 years; height, -4.2 +/- 0.5 SDS) and five children with ISS (aged 11.1 +/- 1.2 years; height, -3.2 +/- 0.1 SDS) were studied. Intravenous bolus infusions of GHRH1-29NH2 (1 micrograms/kg), GHRP-2(1 microgram/kg), and GHRH plus GHRP-2 (each 1 micrograms/kg), were administered in a randomized order. Because of the variability of GH responses, results were analyzed by a nonparametric statistical method. Patients in group A showed low GH responses to both GHRH1-29NH2 and GHRP-2 stimulation: in only three of 10 and one of nine cases, respectively, were the peak GH levels above 5.0 micrograms/L. GH area under the curve (AUC) 90 minutes after GHRP-2 administration was slightly less than for GHRH1-29NH2 (179 +/- 150 v 214 +/- 68 micrograms/L.min, P = .06). In group B, GH responses to GHRH1-29NH2 and GHRP-2 were approximately of the same magnitude (1,943 +/- 819 v 1,981 +/- 887 micrograms/L.min, P = .9).(ABSTRACT TRUNCATED AT 250 WORDS)

[Immunoanalysis of free alpha-subunits of glycoprotein hormones in human blood serum and its relationship with pituitary glycoprotein hormones]. / Immunoanaliz svobodnoi alpha-sub"edinitsy glikoproteinovykh gormonov v syvorotke krovi cheloveka i ee vzaimootnosheniia s glikoproteinovymi gormonami gipofiza.

A radioimmunoassay test system has been designed for measurements of free alpha-subunit (AS) of glycoprotein hormones in human blood serum with a sensitivity of 0.15 ng/ml. This test system revealed the absence of a direct correlation between the levels of free AS and levels of glycoprotein hormones in the blood sera of women with various endocrine profile, this being indicative of the specificity of this test system, on the one hand, and, on the other, confirming the possibility of independent secretion by the pituitary of free AS into the blood. Basal blood serum level of free AS in normal subjects is low: 0.9 ng/ml in women aged 17 to 30. The level of free AS secretion in the blood of many patients with nonfunctioning tumors of the pituitary was found increased, this demonstrating the diagnostic significance of measuring free AS as a marker of such tumors.

[Use of monoclonal antibodies for immunosorption of growth hormone from human biological tissues and fluids]. / Ispol'zovanie monoklonal'nykh antitel dlia immunosorbtsii gormona rostaiz bioligicheskikh tkanei i zhidkostei cheloveka.

An immunosorbent with high binding capacity was developed using monoclonal antibodies specific to human growth hormone. Potential activity of the sorbent was studied in isolation of growth hormone from biological tissues and fluids. The immunosorbent enabled one to isolate the biologically and immunologically active growth hormone with high purity from the hypophyseal extract using only one step of purification. As shown by affinity chromatography and subsequent electrophoresis in polyacrylamide gel combined with radioimmunoblotting, together with predominant form of growth hormone, also intact and secreted from hypophysis, two-chain form of the hormone arising after proteolysis and large immunoreactive hormone fragments were detected in human circulation. These derivatives of the hormone may be also excreted with urine in unaltered form.

[Heterogeneity of immunoreactive prolactin in hyperprolactinemia of various origin]. / Geterogennost' immunoreaktivnogo prolaktina pri giperprolaktinemii razlichnogo geneza.

Study of molecular heterogeneity of immunoreactive prolactin in patients with macro- and microprolactinomas and idiopathic hyperprolactinemia has shown heterogeneity of the total blood immunoreactive prolactin pool in all the examined patients. This pool included three basic forms with molecular masses about 23, 50, and over 100 kD (23K-, 50K-, 100K-prolactin), whose ratios essentially differed in individual patients. Physiologically the most active monomeric 23K form of prolactin predominated in the blood of patients with hyperprolactinemia due to hypophyseal micro- and macroadenomas, parallelled by manifest signs of galactorrhea and hypogonadism; the content of this form may reach 95% of the total immunoreactive hormone. Patients with hyperprolactinemia of obscure origin present with quite the contrary ratio of prolactin immunoreactive forms with the predominance of high-molecular 100K form of the hormone, whose share may reach 80-90%. Such cases of hyperprolactinemia may be associated with the absence of clear-cut clinical manifestations, including such as galactorrhea and menstrual cycle disorders, and with inefficacy of traditional therapy. Such cases were tentatively classified as 'the high-molecular prolactin syndrome' and need further research.

[Physico-chemical, immunochemical, and biological activity of prolactin from human amniotic fluid]. / Fiziko-khimicheskaia, immunokhimicheskaia i biologicheskaia kharakteristika prolaktina amnioticheskoi zhidkosti cheloveka.

Highly purified preparation of prolactin with molecular mass 23 kDa, which is the main form of the hormone in human amnionic fluid, was isolated from the fluid using gel filtration on Sephadex G-100, chromatography on DEAE-Sepharose, concanavalin A Sepharose, CM-cellulose. Physico-chemical, immunochemical and biological properties of the amnionic prolactin were studied as compared with those of hypophyseal hormone. Properties of the hormonal forms isolated from both these tissues were similar. The glycosylated form of prolactin with molecular mass 25.0 kDa was detected either in amnionic fluid or in hypophysis.

[Obtaining and morphological characteristics of primary monolayer cell cultures of human somatotropinomas]. / Poluchenie i morfologicheskaia kharakteristika pervichnykh monosloinykh kletochnykh kul'tur somatotropinom cheloveka.

This paper describes the development of method of preparing cell suspension obtained from surgical material of patients with pituitary adenomas and acromegaly as well as the procedure of subsequent long-term cultivation in monolayers of the cells isolated. As judged by visual inspection and measurement of growth hormone and prolactin secretion, tumor pituitary cells kept viability and functional activity for at least 6 days of growing in vitro. Immunocytochemical visualization of somato- and lactotrophs of the same histological preparations permitted us to show that vast majority of cultured cells is represented by somatotrophs; however, a small portion of cell population is represented by lactotrophs and lactosomatotrophs. The peculiarities of cytoarchitectonics in two types of cell cultures of human somatotropinomas were studied.

[Regulation of hormone secretion in primary cell cultures of human somatotropinomas]. / Reguliatsiia gormonal'noi sekretsii v pervichnykh kletochnykh kul'turakh somatotropinom cheloveka.

The effects of somatostatin and thyroliberin (thyrotropin-releasing hormone; TRH) on growth hormone (GH) and prolactin (PRL) secretion were studied in short-term (0.5-3h) or long-term (21-24h) incubations using monolayer cell cultures of somatotropin obtained from surgical material of patients with acromegaly. High sensitivity of both GH and PRL release to inhibitory action of somatostatin (10(-11) M) was established. We could not reveal the unambiguous influence of TRH on somatotropic function in the in vivo and in vitro conditions, as compared to the action of this tripeptide on PRL secretion. The results obtained permit us to propose that cell cultures of pituitary adenomata represent adequate and convenient models for studying the pathogenesis of tumor processes in the pituitary gland and for the development of new procedures of pharmacotherapy.