In vitro bioactivity of bioresorbable porous polymeric scaffolds incorporating hydroxyapatite microspheres

Biomimetic composites consisting of polymer and mineral components, resembling bone in structure and composition, were produced using a rapid prototyping technique for bone tissue engineering applications. Solid freeform fabrication, known as rapid prototyping (RP) technology, allows scaffolds to be designed with pre-defined and controlled external and internal architecture. Using the indirect RP technique, a three-component scaffold with a woodpile structure, consisting of poly-L-lactic acid (PLLA), chitosan and hydroxyapatite (HA) microspheres, was produced that had a macroporosity of more than 50% together with micropores induced by lyophilization. X-ray diffraction analysis indicated that the preparation and construction of the composite scaffold did not affect the phase composition of the HA. The compressive strength and elastic modulus (E) for the PLLA composites are 0.42 and 1.46 MPa, respectively, which are much higher than those of chitosan/HA composites and resemble the properties of cellular structure. These scaffolds showed excellent biocompatibility and ability for three-dimensional tissue growth of MC3T3-E1 pre-osteoblastic cells. The pre-osteoblastic cells cultured on these scaffolds formed a network on the HA microspheres and proliferated not only in the macropore channels but also in the micropores, as seen from the histological analysis and electron microscopy. The proliferating cells formed an extracellular matrix network and also differentiated into mature osteoblasts, as indicated by alkaline phosphatase enzyme activity. The properties of these scaffolds indicate that they can be used for non-load-bearing applications.

SNP detection and haplotype analysis in partial sequence of MSTN gene in sheep

Polymerase chain reaction (PCR) products of the MSTN gene amplified from sixty sheep of nine Chinese indigenous sheep breeds and one imported sheep breed were sequenced to identify the single-nucleotide polymorphisms (SNPs) in a 378-bp fragment including intron 2 and exon 3 of the MSTN gene. A total of fifteen SNPs (A1937C, T1942G, C1956T, A1972C, A1990G, A2008C, A2011G, C2019T, A2025C, A2027C, T2085G, T2173C, C2198T, C2210T and C2213T) were detected among the sixty sequenced individuals and they were all located in intron 2. Twelve haplotypes were identified from these fifteen SNPs, of which haplotype I (CGTCGCGTCCGCTTT) and VIII (ATCAAAACAATTCCC) were the two major and basic ones with frequencies of 12.25% and 77.80%, respectively. Haplotype VIII was distributed in all sheep breeds and all individuals of the meat or meat-wool type sheep breeds were homozygous with respect to this haplotype. This suggests that haplotype VIII might be related to meat production traits in sheep. Haplotype I was only distributed in the fur, lambskin type and fur-meat type sheep breeds. This suggests that haplotype I may have some relationship with fur traits in sheep.

Reference values for the arterial pulse wave in Chinese

BACKGROUND

Pulse wave analysis using the SphygmoCor system allows the estimation of central pulse pressure (PP) and peripheral and central augmentation indexes (AIxs). We studied the limits of normality of these measurements in Chinese.

METHODS

We computed limits of normality as the 95% confidence boundaries from regression models relating the arterial indexes to age.

RESULTS

The reference population included 924 subjects (50.7% men, mean age 40.7 years) without overt cardiovascular disease. Men, compared to women, had higher peripheral (43.3 vs. 41.7 mm Hg; P = 0.01) and central (32.9 vs. 30.9 mm Hg; P < 0.0001) PPs, but lower peripheral (69.0 vs. 74.2%; P < 0.0001) and central (16.6 vs. 21.0%; P < 0.0001) AIxs. All arterial measurements showed a curvilinear relation with age. Both before and after adjustment for confounding factors, peripheral and central PPs increased less (P < or = 0.01) with age in men than in women, whereas the relation of peripheral and central AIxs with age was similar (P > or = 0.13) in both sexes. In 40-year-old Chinese, approximate thresholds for peripheral and central PPs, peripheral and central AIxs were 58 mm Hg, 48 mm Hg, 105% and 45%, respectively. Considering the age range from 20 to 60 years, thresholds varied within approximately 5 mm Hg, approximately 10 mm Hg, approximately 20%, and approximately 15% of the aforementioned thresholds for peripheral and central PPs, peripheral and central AIxs, respectively.

CONCLUSIONS

Pending further validation in prospective studies, our present study provides preliminary diagnostic thresholds for PP and AIxs in Chinese.

Polymorphism of the PRNP gene in the main breeds of indigenous Chinese goats

The polymorphism of the PRNP gene plays a key role in susceptibility to prion disease. Scrapie is a neurodegenerative disease affecting sheep and goats and belongs to the group of prion diseases. We isolated DNA from 333 goat samples representing the main local goat breeds in six provinces in China to identify PRNP polymorphisms and to determine whether these breeds were at risk for developing scrapie. Two novel amino acid polymorphisms (R211G and T219I) and a novel silent mutation at codon 125 as well as nine previously reported polymorphisms were observed. Twenty-eight alleles and forty-nine different genotypes were obtained. The codon 142M associated with resistance of goat scrapie was not found in this study. The codon 143R was relatively rare. The codon 222K, a potentially useful candidate site for selecting for scrapie resistance, was also rare in indigenous Chinese goats. These results could provide some useful data for assessing the risk of scrapie in Chinese indigenous goats.

Intraband carrier photoexcitation in quantum dot lasers

We unveil the role of bound-to-continuum photoexcitation of carriers as a relevant process that affects the performance of quantum dot (QD) lasers. We present the response of an InAs/InGaAs QD laser to a sub-band gap pump, showing an unexpected depletion of the emitted photons. We relate this observation with carrier photoexcitation through additional transmission and photocurrent measurements. We provide a theoretical support to the experimental data and highlight the important role of this process in the laser characteristics.

Rangeland degradation and restoration management in China

Rangelands of China have for centuries provided forage for livestock but now their role in water, soil, and biodiversity conservation is being recognised by Governments and people. However, much of the rangelands has recently degraded and desertification is now a widespread problem. The cause of the degradation is over-grazing and over-cultivation. Climate change is exacerbating the problem. The Chinese Governments have begun to address these severe problems through policy adjustments and projects. In parallel, some research and development is taking place. There are major impediments to addressing the problem; the importance of rangelands to China and its people are generally underestimated, legislative protection is incomplete and often ineffective, little attention is paid to scientific knowledge for development of management of natural resources, there is insufficient technological support, and Governments are not able to invest sufficiently to effectively restore and develop rangeland natural resources. However, with this background we propose how the problems might be more effectively addressed in the future.

Effects of adrenalectomy on the excitability of neurosecretory parvocellular neurones in the hypothalamic paraventricular nucleus

Glucocorticoids are well known to inhibit the release of hypophysiotrophic hormones from neurones originating in the paraventricular nucleus (PVN), but the cellular mechanisms of the inhibition are not well understood. Here, we examined the effects of adrenalectomy (ADX) on the spontaneous firing activity in the neurosecretory parvocellular PVN neurones of rat brain slices. The neurones were identified by injecting a retrograde dye into the pituitary stalk and classified according to their electrophysiological properties. The intranuclear distribution, electrophysiological properties, and hypophysiotrophic hormone phenotype of the labelled type II PVN neurones were similar to neurosecretory parvocellular PVN neurones. In the neurones of sham-operated rats under the cell-attached recording mode, we observed three spontaneous activity patterns: tonic regular (24%), tonic irregular (36%), and silent (40%). Noradrenaline (100 microM) induced an excitatory or an inhibitory effect on the spontaneous activity. Noradrenergic excitation was blocked by prazosin (2 microM, alpha(1)-adrenoceptor antagonist), and mimicked by phenylephrine (100 microM, alpha(1)-adrenoceptor agonist), whereas noradrenergic inhibition was blocked by yohimbine (2 microM, alpha(2)-adrenoceptor antagonist) and mimicked by clonidine (50 microM, alpha(2)-adrenoceptor agonist). In the neurones of ADX rats, we found burst firing in 35% of neurones tested and an increase in the frequency of spontaneous firing. The burst firing was not observed in the neurones of the sham-operated rats. ADX caused a 1.7-fold increase in the proportion of neurones showing the noradrenergic excitation. Supplementation of the ADX rats with corticosterone (10 mg pellet) reversed the ADX-induced burst firing, and the potentiation of noradrenergic excitation. In summary, our results show that removal of corticosterone by ADX can elevate the neuronal excitability by increasing the spontaneous firing rate and by potentiating the alpha(1)-adrenoceptor-mediated noradrenergic excitation, and it can facilitate hormone release by inducing burst firing. Our results provide new insight to the cellular mechanisms of the feedback inhibition by glucocorticoids in the neurosecretory parvocellular neurones of the PVN.

Rapid and efficient nonviral gene delivery of CD154 to primary chronic lymphocytic leukemia cells

Interactions between CD40 and CD40 ligand (CD154) are essential in the regulation of both humoral and cellular immune responses. Forced expression of human CD154 in B chronic lymphocytic leukemia (B-CLL) cells can upregulate costimulatory and adhesion molecules and restore antigen-presenting capacity. Unfortunately, B-CLL cells are resistant to direct gene manipulation with most currently available gene transfer systems. In this report, we describe the use of a nonviral, clinical-grade, electroporation-based gene delivery system and a standard plasmid carrying CD154 cDNA, which achieved efficient (64+/-15%) and rapid (within 3 h) transfection of primary B-CLL cells. Consistent results were obtained from multiple human donors. Transfection of CD154 was functional in that it led to upregulated expression of CD80, CD86, ICAM-I and MHC class II (HLA-DR) on the B-CLL cells and induction of allogeneic immune responses in MLR assays. Furthermore, sustained transgene expression was demonstrated in long-term cryopreserved transfected cells. This simple and rapid gene delivery technology has been validated under the current Good Manufacturing Practice conditions, and multiple doses of CD154-expressing cells were prepared for CLL patients from one DNA transfection. Vaccination strategies using autologous tumor cells manipulated ex vivo for patients with B-CLL and perhaps with other hematopoietic malignancies could be practically implemented using this rapid and efficient nonviral gene delivery system.

Salmonellosis outbreak among factory workers--Huizhou, Guangdong Province, China, July 2004

INTRODUCTION

During July 9--14, 2004, an outbreak of gastroenteritis occurred among workers at an electronics factory in Huizhou, Guangdong Province, China; 199 cases were reported. A case-control investigation was initiated to identify the agent and the mode of transmission.

METHODS

Stool samples were collected from 142 workers and food handlers and cultured for enteric pathogens. A questionnaire concerning meals and foods eaten in the factory cafeteria during July 11--13 was administered to 92 ill workers and 100 controls.

RESULTS

Of approximately 2,000 workers who worked during the outbreak, 197 (10%) had illness consistent with the case definition. Salmonella enteritidis was identified from 44 (31%) of 142 stool samples collected from ill workers. Ill workers were more likely than controls to have eaten breakfast in the factory cafeteria during July 11--13. Of eight foods served at breakfast in the factory cafeteria, three were associated with illness: cake, bread (on July 12 only), and congee (i.e., rice porridge). Stratification of bread and congee exposure by cake consumption indicated that only bread eaten on July 12 was associated with gastroenteritis. The cake was baked on July 11, and a mixture that included raw eggs was poured on top; the cake was then stored at room temperature and served for breakfast on 3 consecutive days (July 11--13). The bread was stored together with the cake on July 11 and 12. No leftover food was tested.

DISCUSSION

The investigation indicated that an outbreak of S. enterica serotype Enteritidis resulted from consumption of an unusual food vehicle (i.e., cake) that had been contaminated from a more typical source (i.e., raw eggs). The bread was stored at room temperature together with cake on which a mixture made from raw eggs had been poured. The bread was probably contaminated by contact with the cake.

CONCLUSION

Food handlers should be instructed that intact fresh eggs can harbor S. enteritidis, foods made from eggs must be cooked, and prepared food must be stored under refrigeration.

Seedling and Adult Plant Resistance to Powdery Mildew in Chinese Bread Wheat Cultivars and Lines

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is a widespread wheat disease in China. Identification of race-specific genes and adult plant resistance (APR) is of major importance in breeding for an efficient genetic control strategy. The objectives of this study were to (i) identify genes that confer seedling resistance to powdery mildew in Chinese bread wheat cultivars and introductions used by breeding programs in China and (ii) evaluate their APR in the field. The results showed that (i) 98 of 192 tested wheat cultivars and lines appear to have one or more resistance genes to powdery mildew; (ii) Pm8 and Pm4b are the most common resistance genes in Chinese wheat cultivars, whereas Pm8 and Pm3d are present most frequently in wheat cultivars introduced from CIMMYT, the United States, and European countries; (iii) genotypes carrying Pm1, Pm3e, Pm5, and Pm7 were susceptible, whereas those carrying Pm12, Pm16, and Pm20 were highly resistant to almost all isolates of B. graminis f. sp. tritici tested; and (iv) 22 genotypes expressed APR. Our data showed that the area under the disease progress curve, maximum disease severity on the penultimate leaf, and the disease index are good indicators of the degree of APR in the field. It may be a good choice to combine major resistance genes and APR genes in wheat breeding to obtain effective resistance to powdery mildew.

Genetic polymorphisms of the HCR gene and a genomic segment in close proximity to HLA-C are associated with patients with psoriasis in Taiwan

BACKGROUND

Although psoriasis vulgaris (PV) is strongly associated with HLA-Cw*0602, it has been proposed that the association of Cw*0602 is due to linkage disequilibrium and that other nearby genes are involved in PV susceptibility. The alpha-helix coiled-coil rod homologue (HCR) gene, located 110 kb telomeric to the HLA-C locus, is presumed to be one of the PV candidate genes. Recently, a 10-kb genomic segment, centromeric to HLA-C, defined by two new single nucleotide polymorphisms (SNPs) n.7*A and n.9*C, was found to have a stronger association with psoriasis than the HCR gene. Until now, no study of the association of the HCR gene, SNPs n.7, and n.9 has been conducted on Chinese patients with psoriasis.

OBJECTIVES

We aimed to determine whether the genetic polymorphisms of the HCR gene, SNPs n.7*A, and n.9*C were associated with an increased risk of psoriasis in Chinese patients.

METHODS

Using direct sequencing of the HCR gene and the genomic region containing SNPs n.7 and n.9, we investigated the HCR gene, SNPs n.7, and n.9 for disease association in 115 Chinese patients with psoriasis and 103 control subjects. The HCR SNPs were confirmed by denaturing high performance liquid chromatography. Genotyping for HLA-Cw*0602 was also carried out using sequence-based typing.

RESULTS

We observed a different allelic distribution between patient and control groups at nucleotide positions 386, 404, 1802 and 2406 of the HCR gene, and SNPs n.7, and n.9. The associations were much stronger in early onset PV patients (for HCR-386*T and HCR-404*T, odds ratio = 5.63, Pc < 0.0001). The HLA-Cw*0602 also displayed a similar association with PV (odds ratio = 5.4, Pc < 0.0001). Moreover, SNP n.7*A, SNP n.9*C, Cw*0602, HCR-386*T, HCR-404*T and HCR-1802*T were in linkage disequilibrium with each other. Haplotype-based association analysis showed SNP n.7*A-SNP n.9*C-Cw*0602-HCR-386*T-HCR-404*T-HCR-1802*T-HCR-2406*G as a major susceptibility haplotype in this Chinese population (for early onset patients, odds ratio = 5.15, Pc < 0.0001).

CONCLUSIONS

Our results indicate that the HCR gene, SNP n.7*A, and SNP n.9*C as well as Cw*0602 are major susceptibility markers for psoriasis in Chinese patients.

Subtypes of alpha1- and alpha2-adrenoceptors mediating noradrenergic modulation of spontaneous inhibitory postsynaptic currents in the hypothalamic paraventricular nucleus

Noradrenergic inputs to the hypothalamic paraventricular nucleus (PVN) play important roles in the regulation of neuroendocrine and autonomic functions. Previous reports show that noradrenaline increases the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in a subpopulation of type II neurones, acting via alpha(1)-adrenoceptors (ARs), but reduces this frequency in most type I and another subpopulation of type II neurones, via alpha(2)-ARs on presynaptic GABA neurones. Here, we identified the subtypes of alpha-ARs mediating noradrenaline-induced increases and decreases in the sIPSC frequency of PVN neurones, by using slice patch recordings from PVN neurones. In both type I and II neurones, the noradrenaline-induced decrease in sIPSC frequency was completely blocked by BRL44408 (alpha(2A)-AR antagonist) at 1-3 micro M, which is approximately 1/100 of its equilibrium dissociation constant (pA(2) = 8.0), but not by prazosin (20-100 micro M, alpha(2B/C)-AR antagonist; pA(2) = 7.5). The effect of noradrenaline was mimicked by guanfacine (alpha(2A)-AR agonist) with an EC(50) of 0.1 micro M. In type II neurones, the noradrenaline-induced increase in sIPSC frequency was not blocked by any of the following antagonists: RS17053 (10 micro M, alpha(1A)-AR antagonist), BMY7378 (2 micro M, alpha(1D)-AR antagonist), prazosin (0.1 micro M, alpha(1)-AR antagonist; pA(2) = 10.5), or chloroethylclonidine (10 micro M, alpha(1B/D)-AR antagonist). However, the effect of noradrenaline was blocked by higher concentrations of prazosin (1 micro M) or RS17053 (100 micro M), suggesting the involvement of alpha(1L)-subtype, a low affinity form of alpha(1A)-ARs. Collectively, our results indicate that the alpha(2A)-, or alpha(1L)-ARs on the GABA neurones mediate the noradrenaline-induced decreases, or increases in the frequencies of the sIPSCs of PVN neurones, respectively.

Transdifferentiation of neoplastic cells

Transdifferentiation is a process in which a stable cell's phenotype changes to that of a distinctly different cell type. It occurs during certain physiological processes and leads to transition of tumor cell phenotypes. The latter process includes neoplastic epithelial-epithelial transition, neoplastic epithelial-mesenchymal transition, neoplastic mesenchymal-epithelial transition and transition between non-neural and neural neoplastic cell. This phonomenon is exemplified in some origin-debated tumors, such as carcinosarcoma, pleomorphic adenoma, synovial sarcoma, Ewing's/pPNET, and malignant fibrohistiocytoma. We propose that differentiation disturbance of cancer cells should include not only undifferentiation and dedifferentiation, but also transdifferentiation as well. Tumor cell transdifferentiation may be influenced or determined by cellular genetic instabilities, proliferation and apoptosis, as well as by extracellular matrix and growth factors.

Protein kinase activity is central to rat germ cell apoptosis induced by methoxyacetic acid

Methoxyacetic acid (MAA) is a major metabolite of ethylene glycol monomethyl ether (EGME). Previous investigations of the testicular lesion induced by EGME have found that dividing meiotic cells are the most sensitive, although several stages of spermatocytes are also vulnerable. Preliminary data from this lab suggested the involvement of protein kinase activity in the development of this lesion, a hypothesis explored in the present studies. We used cultured seminiferous tubules (STs) from juvenile rats (25-day-old), exposed in vitro to MAA and several inhibitors of protein kinases. Nineteen h following a 5-h exposure to 5 mM MAA (the plasma level in vivo after a toxic dose of EGME), apoptotic spermatocytes were seen in early- and late-stage STs. Cell death was prevented by cotreatment with broad-spectrum inhibitors of protein kinases such as H-7, H-8, K-252a, W-7, and genistein. In corroboration, immunocytochemistry with antibodies to various kinases (PKCmu, zeta, and gamma, AKAP220, CaMKII, MLCK, and Src) showed increased staining around dying spermatocytes following EGME treatment in vivo. 2D-PAGE, autoradiography, and nanospray mass spectrometry was used to separate and identify proteins whose phosphorylation status was most greatly changed following exposure to MAA. One protein was identified by sequence analysis as being glucose-regulated protein 94 (grp94). Westem blotting and immunocytochemistry confirmed this finding. The data we present implicate kinase activities in the pathogenesis of this lesion and suggest the involvement of Sertoli cells.

Transdifferentiation in neoplastic development and its pathological implication

Transdifferentiation is a process in which a cell committed to a particular specialization changes to another quite distinct type. It occurs during embryological development and some pathological processes, and causes the tumor cells to express a phenotype different from that of their normal progenitors. Neoplastic transdifferentiation involves pathogenesis of cancer subtype, transition between neoplastic epithelia and neuroendocrine cell, transition between neoplastic epithelia and mesenchyme, as well as transition between non-neuroectodermal and neuroectodermal cells. We propose that differentiation disturbance of cancer cells should include not only lower-, un-, or de-differentiation, but also transdifferentiation. Tumor cell transdifferentiation results from genetic instabilities. In some type of neoplastic transition, the initiation may be induced by extracellular matrix and growth factors.

[The experimental study on protective effects and its mechanisms of interleukin-1 receptor antagonist on isolated swine kidney with ischemia/reperfusion]

AIM

To observe the protective effects and approach its mechanisms of interleukin-1 receptor antagonist (IL-1ra) on the isolated swine kidney with ischemia/reperfusion (IR).

METHODS

Thirty two swine were divided randomly into control group (n = 11), IR group (n = 11) and IL-1ra treatment group (IL-1ra group, n = 10) in the study. All swine were electrified. The kidneys were removed and put in ice-box immediately for detecting in control group. In IR group and IL-1ra group, reperfusion pressure and flow rate were both observed once every 30 minutes, the urine at the time of reperfusion 2 hours and the renal cortex at the time of reperfusion 2 hours and 30 minutes were taken for detecting.

RESULTS

The resistance of perfusion in IL-1ra group was much lower than that in the IR group during reperfusion except start of reperfusion, there was a significant difference between IR group and IL-1ra group (P < 0.05, under the same). The content of MDA,TNF-alpha and IL-8 in the renal cortex in IR group were higher and the activities of SOD and Na(+) -K(+) -ATPase were lower than those in control group, In IL-1ra group, the content of MDA and the activity of SOD in renal cortex was respectively higher or lower than that in control group. Compared with IR group, the content of MDA and TNF-alpha and IL-8 in the renal tissues and urine protein were lower and the activities of SOD and Na(+) -K(+) -ATPase were higher in IL-1ra group. The serious degeneration and necrosis of renal tissue were observed in IR group under light microscope and electron microscope, but there was only slight degeneration in IL-1ra group.

CONCLUSION

The results indicated that IL-1ra were effective in protecting the isolated swine kidney from IR injury.

[Research of ultra-structural pathological changes of nervous, endocrine and immune system in heroin addicts]

OBJECTIVE

To investigate ultrastructural pathological changes of Heroin-Addicts.

METHODS

Heroin-Addicts' central nervous system, endocrine system, immune system and reproductive system in 4 cases are observed by using transmission electron microscope(TEM).

RESULTS

The changes of central nervous system are mitochondrion swelling, crista fragmentation and disappear. Endoplasmic reticulum dilation, nervous fibres and cell organelles reduction; mitochondrion swelling, Partial crista fragmentation and endoplasmic reticulum dilation are also found in endocrine system; Lymphocytes reduction, cytoplasm ingredient reduction and dead lymphocytes increase in immune system; in reproductive system, spermatogenic cells and cell organelles are reduced in the male and follicle disappeared in the female.

CONCLUSION

Ultra-structural pathological changes of heroin-addicts are presented acute, chronic oxygen deficiency degeneration and necrosis.

High-efficiency electrotransfection of human primary hematopoietic stem cells

A major obstacle to gene transfer into hematopoietic stem cells, a key step for many gene therapy and tissue replacement applications, is its low efficiency. High cell mortality is responsible for the low efficiency of electrotransfection when this technique is applied to certain 'refractory' cell types such as hematopoietic stem cells. Using human primary CD-34+ cells from peripheral blood as a model, we found that transfection-induced apoptosis and, to a lesser extent, postpulse colloidal-osmotic swelling are two main factors for the poor transfection of these cells. By applying caspase inhibitors (B-D-Fluomethyl Ketone and Z-VAD-FMK) to reduce apoptosis, and by using the postpulse pelleting method to suppress colloidal-osmotic swelling, we achieved a transfection efficiency of ~20%, regardless of the presence of cytokines in the suspension medium. This effort brings the ex vivo electrotransfection efficiency within the reach of therapeutic applications.

Gonocyte-Sertoli cell interactions during development of the neonatal rodent testis

During neonatal testicular development in the rat, events critical for subsequent germ cell development occur that set the stage for fertility later in life. Some gonocytes resume mitotic activity and/or migrate to the surrounding basal lamina, and use of a carefully defined Sertoli cell-gonocyte coculture system indicates that these crucial events occur without added factors or hormones and are hence likely to depend on interaction with adjacent Sertoli cells. Coupling of the Kit receptor protein on gonocytes to stem cell factor from Sertoli cells is vital for successful migration by gonocytes, as antagonism of the former suppresses and addition of the latter stimulates gonocyte migration. During the neonatal period, intercellular adhesion is modified in a developmental manner such that neural cell adhesion molecule (NCAM) is the main adhesive molecule expressed and functioning at birth, with a progressive decline as development proceeds. This decline in NCAM expression is supported by the addition of exogenous 3,3',5-triiodothyronine in vitro, and because this factor is recognized as supporting Sertoli cell differentiation, it seems likely that changing intercellular adhesion is a function of progressive development of Sertoli cells. Other avenues whereby maturing testicular cells influence each other doubtless exist, including secretion of growth factors and other peptides and developmentally important changes in the makeup of the extracellular matrix, which Sertoli cells and gonocytes contact. Continued investigation in these areas will be very valuable in enlarging our understanding of how neonatal testicular development provides the basis for successful spermatogenesis.

[The types of respiratory neurons in nucleus paragigantocellularis lateralis in rats and their responses to some medicines]

AIM AND METHODS

In 36 anesthetized spontaneously breathing Sprague-Dawley rats, the types of respiratory neurons and the state of neurotransmitters and receptors in nucleus paragigantocellularis lateralis (PGCL) were studied with extracellular recording technique and multibarrel microelectrode techniques.

RESULTS

At the caudal part of the PGCL(cPGCL) in 14 rats, a total of 39 respiratory neurons (RNs) were recorded including 24 inspiratory, 12 expiratory and 3 phase-spanning neurons. At the cPGCL in another 22 rats, we discovered that out of 14 RNs tested, 12 were excited by iontophoretic application of sodium glutamate (L-GLu), and all the 22 RNs tested were inhibited by gamma-aminobutyric acid (GABA). DL-2-amino-5-phosphonovaleric acid (AP5), an antagonist of N-methyl-D-aspartate (NMDA) receptor, and bicuculline (BIC), an antagonist of GABA(A) receptor, both showed three kinds of effects on the RNs discharge: excitatory, inhibitory and no-effect. AP5 could block partially the excitatory effect of L-GLu on a large part of RNs tested (6/9). BIC blocked, partially or completely, the inhibitory effect of GABA also on a large part of the RNs tested (9/11).

CONCLUSION

It is implied that PGCL is one of the important neural substrates responsible for the regulation of respiration. There might exist endogenous glutamate and GABA acting as neurotransmitters in the cPGCL area and excitatory amino acids (including NMDA and non- NMDA) and GABA(A)-receptors on cPGCL neurons. These neurotransmitters and receptors may mediate the regulatory action of cPGCL on respiration.

[Studies on the distribution of actin during meiotic prophase I of Nicotiana rustica L]

The Pollen Mother Cells of Nicotiana Rustica L. were studied using the techniques of immunofluorescence microscopy and protein A-colloidal gold IEM. Immunofluorescence microscopy indicates the presence of actin in both nuclei and cytoplasm. IEM observation shows that gold particles are present in cytoplasm, chromatin and cytomictic channels. These results indicate that actin has some relation with chromatin condensing at synizesis. Moreover, actin may also play an important role in cytomixis.