Convergent input from brainstem coincidence detectors onto delay-sensitive neurons in the inferior colliculus

Responses of low-frequency neurons in the inferior colliculus (IC) of anesthetized guinea pigs were studied with binaural beats to assess their mean best interaural phase (BP) to a range of stimulating frequencies. Phase plots (stimulating frequency vs BP) were produced, from which measures of characteristic delay (CD) and characteristic phase (CP) for each neuron were obtained. The CD provides an estimate of the difference in travel time from each ear to coincidence-detector neurons in the brainstem. The CP indicates the mechanism underpinning the coincidence detector responses. A linear phase plot indicates a single, constant delay between the coincidence-detector inputs from the two ears. In more than half (54 of 90) of the neurons, the phase plot was not linear. We hypothesized that neurons with nonlinear phase plots received convergent input from brainstem coincidence detectors with different CDs. Presentation of a second tone with a fixed, unfavorable delay suppressed the response of one input, linearizing the phase plot and revealing other inputs to be relatively simple coincidence detectors. For some neurons with highly complex phase plots, the suppressor tone altered BP values, but did not resolve the nature of the inputs. For neurons with linear phase plots, the suppressor tone either completely abolished their responses or reduced their discharge rate with no change in BP. By selectively suppressing inputs with a second tone, we are able to reveal the nature of underlying binaural inputs to IC neurons, confirming the hypothesis that the complex phase plots of many IC neurons are a result of convergence from simple brainstem coincidence detectors.

[Metastatic potential correlates with cell surface carbohydrate profiles of nasopharyngeal carcinoma]

In order to investigate the changes in glycoprotein structure between non-metastatic and metastatic cells of nasopharyngerl carcinoma (NPC), peanut agglutinin (PNA), ulex europeaus (UEA-I) and concanavalin ensifomis agglutinin (ConA) staining were used to examine 102 nasopharyngeal carcinoma tissues (84 primary tumors and 18 metastatic lymph nodes) with the avidin-biotinperoxidase complex method. PNA reaction was positive in most cells of nasopharyngeal carcinomas regardles of in histopathologic type, the degree of differentiation and metastasis. The levels of UEA-I receptors apparently increased during nasopharyngeal carcinoma progression from non-metastatic to metastatic tumors. The binding to ConA clearly decreased in the cells of metastatic cases and metastatic lymph node. So, the increased expression of UEA-I receptors and decrease of ConA receptors on tumor cells might have been implicated in the expression of metastatic potential.

[Applied anatomy of the vascularity in the ileocolic region and its clinical significance]

To understand the characteristics of the patterns of arteries and veins distributed over the ileocolic segment, 50 cadavers were studied by gross-anatomy. The arteries, veins and their paracolic anastomoses distributed over ileocecal region, ascending colon and transverse colon were observed. The results showed that the distribution pattern of venous vessel was far more constant than that of artery, that the arrangements of artery in the ileocolic segment were classified into 7 types, and there were no interruption of paracolic anastomoses between arteries. But in 3 specimens the paracolic anastemoses between the right colic vein and the middle colic vein were completely interrupted. These findings may be useful in guiding clinical practice and preventing postoperative complications in ileocolic replacement of esophagus.

Embryonic entorhinal transplants partially ameliorate the deficits in spatial memory in adult rats with entorhinal cortex lesions

Our previous studies have demonstrated that axons from grafts of embryonic entorhinal cortex (EC) can reinnervate the deafferented zones in the hippocampus and form synaptic connections with the host dentate gyrus in adult mice and rats deprived of their own entorhinal inputs. Here, we have examined the ability of the EC grafts to ameliorate deficits in spatial memory. Three months after transplantation, the grafted rats and control animals were subjected to Morris water maze testing followed by histological examination. According to the exact position of grafts in the host brain, the rats with lesion and EC transplants were divided into two groups, one with EC grafts contacting both the hippocampus and overlying neocortex (n=7, EC1) and another with EC grafts confined within the hippocampus (n=6, EC2). While EC2 rats were still as impaired as those with lesion and transplants of non-entorhinal cortex (n=10, NEC) or with lesions only (n=7, LES), the EC1 rats performed better than the LES group. In a spatial memory trial, the EC1 group made more crossings over platform site and showed more focused search behavior than EC2, LES, NEC groups. The data suggest that EC grafts could partially ameliorate the deficit in spatial learning behavior in the EC-lesioned adult rats. The requirement for the graft to contact both the neocortex and the hippocampus suggests that the functional effects may be exerted by the formation of new neocortical-EC graft-hippocampal circuits.

Expression of TGFalpha autocrine activity in human colon carcinoma CBS cells is autoregulated and independent of exogenous epidermal growth factor

Autocrine transforming growth factor alpha (TGFalpha) activity and control mechanisms for its expression were examined in a representative clonal isolate (CBS4) of a well-differentiated human colon carcinoma cell line designated CBS. CBS4 cells expressed TGFalpha and its receptor, epidermal growth factor receptor (EGFr). Blockade of EGFr and TGFalpha by neutralizing antibodies inhibited clonal growth and the initiation of DNA synthesis from quiescence in CBS4 cells. Therefore, TGFalpha is an autocrine growth factor for CBS4 cells. Several studies have indicated that activation of the EGFr by exogenous EGF stimulates TGFalpha expression. However, in CBS4 cells EGF did not induce TGFalpha mRNA expression, indicating that EGF does not affect TGFalpha transcription in these cells. Exogenous treatment of exponentially growing cells with either EGF or EGFr blocking antibody enhanced release of TGFalpha protein into the conditioned medium. This indicated that the release of TGFalpha into the conditioned medium by exogenous EGF was at least partially due to the displacement of TGFalpha from the TGFalpha/EGFr complexes. Similarly to exponentially growing cells, the EGFr blocking antibody and EGF also enhanced TGFalpha release into the medium of CBS4 cells after release from quiescence. These results indicated that exogenous EGF had little if any effect on TGFalpha expression in these cells and suggested that TGFalpha expression might be under endogenous TGFalpha control. Blockade of the autocrine TGFalpha loop by TGFalpha neutralizing antibody suppressed TGFalpha mRNA both in exponentially growing and quiescent cells, demonstrating that autocrine TGFalpha is autoregulatory in this system.

[The role of nitric oxide and nitric oxide synthase in the pathogenesis of asthma]

OBJECTIVE

To investigate the role of nitric oxide (NO) and nitric oxide synthase (NOS) in the pathogenesis of asthma.

METHOD

52 guinea pigs were randomly divided into four groups of 13 each: (1) asthmatic group (Group A): Dunkin-Hartley guinea-pigs were injected celiacly with 1 ml of 10% ovalbumin (OA). After 14 days, the animals were inhaled with an aerosol of 1% OA for 40-60 seconds for 10 days every other day; (2) Corticosteroid prevention group (Group CT): As above, just before the animals were inhaled with an aerosol, 0.5 mg/kg dexamethasone were injected celiacly; (3) N-nitro-L arginine prevention group (Group L): As Group A, just before the animals were inhaled with an aerosol, 0.4 mg/kg LNNA were injected celiacly; (4) Controls (Group C): and nitrate (NO2.-/NO3.-) levels in plasma, nitrite bronchoalveolar lavage fluid (BALF) and lung tissues were examined. At the same time, inducible nitric oxide synthase (iNOS) and constitute nitric oxide synthase (cNOS) activity levels in the lung tissues were examined, and the changes of cNOS in the guinea pig asthma model lung tissues were observed using histochemical detection.

RESULT

All groups had no significant alteration of NO2.-/NO3.- in the plasma (P > 0.05). Group A had increased amounts of NO2.-/NO3.- in the BALF and in the lung tissues compared with the other groups (BALF: Group A 10.2 +/- 1.3, Group CT 7.2 +/- 1.1, Group L 7.3 +/- 1.3, Group C 6.2 +/- 0.8 mumol/L respectively, all of P < 0.01; the lung tissues: Group A 0.89 +/- 0.07, Group CT 0.16 +/- 0.09, Group L 0.24 +/- 0.09, Group C 0.18 +/- 0.05 nmol/mg respectively, all of P < 0.01). Group A also showed increased amounts of iNOS levels in the lung tissues than the other groups (Group A 59 +/- 18, Group CT 10 +/- 5, Group L 12 +/- 7, Group C 10 +/- 5 pmol/mg respectively, all of P < 0.01). Group L showed decreased amounts of cNOS levels in the lung tissues than the Group C (0.8 +/- 0.4, 1.2 +/- 0.4 fmol/mg, P < 0.05). While there were no significant alterations in the other groups (P > 0.05). Elevation of iNOS in the lung tissues was correlated with NO2-/NO3- in the BALF and in the lung tissues (r = 0.714, 0.842, respectively, P < 0.05, 0.01 respectively). NADPHd was found to be a histochemical marker reflecting cNOS activity. It was found that there was no marked alteration of cNOS activity in the Group A, Group CT and Group C, but lower in the Group L.

CONCLUSION

There is increased production of iNOS in asthmatic guinea pigs, the iNOS produced could cause increased production of NO, and probably cause cytotoxicity and mediate airway hyperresponsiveness. NO and NOS may play an important role in the pathogenesis of asthma.

[A study of gene expression of PDGFBB and PDGFR as well as level of PDGFR activity in human glioma cells]

OBJECTIVE

To investigate the effect of PDGFBB autocrine loop on the development and progression of human gliomas.

METHODS

73 human glioma specimens of different stages were studied using in situ hybridization and immunohistochemical techniques.

RESULTS

62 (84.9%) of 73 cases expressed PDGFB mRNA. The positive rate and the amount of PDGFB mRNA increased correspondingly with the degree of malignancy. All of 73 gliomas expressed PDGFR alpha, PDGFR beta and phosphotyrosine protein (P-Tyr). The positive cell densities of PDGFR alpha, PDGFR beta and P-Tyr correlated positively with one another and increased with the malignancy as well as the expression level of PDGFB mRNA in the gliomas. However, there was no significant difference between positive cell densities of PDGFR alpha and PDGFR beta in any glioma group with different grading.

CONCLUSIONS

PDGFBB autocrine loop existed generally in the glioma cells, the expression levels of PDGFBB and PDGFRs were well correlated with the tumor grading and the positive cell density of P-Tyr which could objectively reflect the activity of PDGFRs and the signal pathways. It's suggested that abnormally increased activity of PDGFBB autocrine loop might play an important role in the development and progression of gliomas.

[Simulation study of selectively stimulating nerve fibers using biphasic pulses]

Biphasic selective stimulation is an effective electrical stimulation mode for preventing nerve fibers against electrochemical damage, for muscle to contract smoothly, and decreasing muscle's fatigue. By use of computer simulation, this paper presents three biphasic stimulation modes respectively using monopolr, bipolar and tripolar electrodes, which can effectively stimulate nerve fibers in a selective way. The results are helpful to the clinical application of neuroelectrical stimulation.

[Studies on trigonometric transform enhancement of chest radiograph based on its anatomical feature]

In this paper, we present a novel trigonometric transform contrast enhancement method for digital chest radiograph, which is based on the anatomical feature of the image processed. With automatic segmenting chest image into a lung region and a non-chest region, a positive linear transform and a negative one are used in lung region and the other region respectively. Therefore, it can enhance the contrast both in lung regions and in mediastinum region up to entire dynamic range of display device.

[Evaluation of the growth and contraction of composite skin]

OBJECTIVE

To evaluate the growth and contraction of different composite skin grafts.

METHODS

The status of the following composite skin grafts was evaluated over 2 years: allogeneic sucking pig dermis and autologous epidermis (group 1, n = 19), allogeneic young pig dermis and autologous epidermis (group 2, n = 7), autologous epidermis (group 3, n = 8). The effects of gestation on the composite skin grafts were also assessed.

RESULTS

It showed that composite skin grafts had smooth surface and no scar formation during 2 to 124 weeks after transplantation. After week 36, the surface area of each group enlarged with different growth rates: group 1 > group 2 > group 3 (P < 0.01). Whole piece grafting was significantly better than joining together of smaller pieces after week 24 (P < 0.001). During pregnancy, CS had good growth ability and elasticity (P < 0.01). Histological study showed that group 1 had rapid growth of skin papillae and epidermal ridges similar to normal skin at week 24.

CONCLUSION

As CS graft with trypsin treated allogeneic sucking pig dermis as a substitute for dermis showed the advantages of rapid growth, good elasticity and stability, it is suggested that it could be used in clinical practice.

Characterization of Escherichia coli endonuclease VIII

Escherichia coli endonuclease VIII (endo VIII) was identified as an enzyme that, like endonuclease III (endo III), removes radiolysis products of thymine including thymine glycol, dihydrothymine, beta-ureidoisobutyric acid, and urea from double-stranded plasmid or phage DNA and cleaves the DNA strand at abasic (AP) sites (Melamede, R. J., Hatahet, Z., Kow, Y. W., Ide., H., and Wallace, S. S. (1994) Biochemistry 33, 1255-1264). Using apparently homogeneous endo VIII protein, we now show that endo VIII removes from double-stranded oligodeoxyribonucleotides the stable oxidative products of cytosine, 5-hydroxycytosine and 5-hydroxyuracil. Endo VIII cleaved the damage-containing DNA strand by beta,delta-elimination as does formamidopyrimidine DNA glycosylase (Fpg). Like Fpg, endo VIII also excised the 5'-terminal deoxyribose phosphate from an endonuclease IV (endo IV) pre-incised AP site. Thus, in addition to amino acid sequence homology (Jiang, D., Hatahet, Z., Blaisdell, J., Melamede, R. J., and Wallace, S. S. (1997) J. Bacteriol. 179, 3773-3782), endo VIII shares a number of catalytic properties with Fpg. In addition, endo VIII specifically bound to oligodeoxynucleotides containing a reduced AP site with a stoichiometry of 1:1 for protein to DNA with an apparent equilibrium dissociation constant of 3.9 nM. Like Fpg and endo III, the DNase I footprint was small with contact sites primarily on the damage-containing strand; unlike Fpg and endo III, the DNA binding of endo VIII to DNA was asymmetric, 3' to the reduced AP site.

Detectability index measures of binaural masking level difference across populations of inferior colliculus neurons

In everyday life we continually need to detect signals against a background of interfering noise (the "cocktail party effect"): a task that is much easier to accomplish using two ears. The binaural masking level difference (BMLD) measures the ability of listeners to use a difference in binaural attributes to segregate sound sources and thus improve their discriminability against interfering noises. By computing the detectability of tones from rate-versus-level functions in the presence of a suprathreshold noise, we previously demonstrated that individual low-frequency delay-sensitive neurons in the inferior colliculus are able to show BMLDs. Here we consider the responses of a population of such neurons when the noise level is held constant (as conventionally in psychophysical paradigms). We have sampled the responses of 121 units in the inferior colliculi of five guinea pigs to identical noise and 500 Hz tones at both ears (NoSo) and to identical noise but with the 500 Hz tone at one ear inverted (NoSpi). The result suggests that the neurons subserving detection of So tones in No (identical noise at the two ears) noise are those neurons with best frequencies (BFs) close to 500 Hz that respond to So tones with an increase in their discharge rate from that attributable to the noise. The detection of the inverted (Spi) signal is also attributable to neurons with BFs close to 500 Hz. However, among these neurons, the presence of the Spi tone was indicated by an increased discharge rate in some neurons and by a decreased discharge rate in others.

[A method based on the theory of stochastic recursive identification for lossless compression of medical images]

This paper describes a method based on the theory of stochastic recursive identification for lossless compression of medical images detail. The performances of this method are compared with the existing method of DPCM through ten X-ray chest images. The experimental results clearly indicate that this method is very valid to realize lossless compression of medical images.

Evidence of increased endogenous carbon monoxide production in newborn rat endotoxicosis

Carbon monoxide is thought to serve as a new endogenous mediator in the pathogenesis of sepsis and septic shock. In newborn rat endotoxicosis, carbon monoxide levels in the circulation as well as liver, kidney and lung were found to be significantly increased (P < 0.05). Moreover, the elevations of carbon monoxide correlated with enhanced nitric oxide production as indicated by nitrite/nitrate levels (P < 0.05). Our present data showed for the first time that endogenously produced carbon monoxide was increased during the course of shock-like states, which suggested that the role of carbon monoxide in sepsis and septic shock might worth further study.

[Study on p53 protein expression, cell proliferation and apoptosis in benign and malignant brain tumors]

OBJECTIVE

To explore the effect of p53 protein expression in brain tumors on the cell proliferation and apoptosis, and the relationship between above parameters and histological classification and malignant degree of these tumors.

METHODS

The p53 protein expression, cell proliferation and apoptosis of 10 control brain tissues (CBT) and 80 brain tumor samples were studied by in situ cell death detection and immunohistochemistry.

RESULTS

Sixty-nine of the brain tumors (86.3%) expressed p53 protein. The amount of tumor cells positively stained for p53 protein increased with the degree of malignancy. All the CBTs did not express p53 protein. The densities of cells positive for proliferating cell nuclear antigen and Ki-67 antigen staining in tumor groups were higher than that in CBT group and were elevated with the malignant degree and the level of p53 protein expression of the tumors. On the contrary, the density of apoptotic cell in tumor groups was lower than that in CBT group, reducing in accord with the increase of malignancy and the level of p53 protein expression of the tumors.

CONCLUSIONS

These results suggest that above 4 parameters have a referential value for the evaluation of biological behavior of brain tumors. It is clear from the present study that the abnormality of expression and function of p53 protein correlates with the imbalance between cell proliferation and apoptosis. This may be one of the important factors in the development and progression of primary and metastatic brain tumors.

[Photoluminescence and UV-Vis absorption spectra characteristics of metal complexes of 8-hydroxyquinoline]

8-hydroxyquinoline complexes of Na(I), Ca(II), Mg(II), Zn(II), Cu(II), Mn(II), Al(III), In(III) and La(III) were synthesized. Photoluminescence (PL) and UV-Vis absorption spectra characteristics of these complexes and 8-hydroxyquinoline are reported. Except complexes of Cu and Mn, most of these complexes reveal photoluminescence. With the polarization force of metal cations increasing, the PL peak shows red-shift and two broad absorption peak in UV-Vis (300-400nm) absorption spectra distinctly appears apart.

[Dual-energy separation imaging on an X-ray direct digital imaging system]

A method of dual-energy separation of bone and soft tissue images of chest based on an X-ray direct digital imaging system has been investigated. In this paper, the optimal thickness of the filter for high energy X-ray beam is discussed. An algorithm of correction of scattered radiation is employed before the separation algorithm. The separated images will be shown in the paper. The result shows that it is possible to use an ordinary broad spectral X-ray beam to acquire the dual-energy images for routine X-ray diagnosis.

[The expression of hsp70 and BCL-2 genes in hippocampus of the rats exposed to cerebral ischemia and reperfusion]

In order to study the molecular mechanism of the selective vulnerability in central nervous system, the expression and distribution of hsp70 and BCL-2 gene were detected by using Northern blot analysis, in situ hybridization and histochemistry method in transient forebrain ischemia and reperfusion rats. It was found that hsp70 gene expression occurred and the synthesis of BCL-2 protein was inhibited in hippocampalCA1 region vulnerable to ischemia, while BCL-2 protein was stained strongly and the signals of hsp70 were not observed in CA3 region resistant to ischemia. The results indicate that the expression of hsp70 gene may be not only as a marker for neuron ischemia, but also play a protective role in the neuronal injury. BCL-2, meanwhile, may have neuro-protective effect on the ischemic neurons.

[Effects of lithium on the proliferation of murine high proliferative potential colony-forming cells and granulocyte macrophage colony forming unit in vitro]

The effects of LiCl on the proliferation of high proliferative potential colony-forming cells (HPP-CFC) and granulocyte macrophage colony-forming unit (CFU-GM) from bone marrow of BALB/c mice were observed. The colonies of HPP-CFC were supported by IL-1, IL-6, WEHI-3 conditioned medium (WEHI-3 CM, which contained IL-3) and L929 conditioned medium (L929-CM, which contained M-CSF); the colonies of CFU-GM were supported by WEHI-3 CM. It was shown that LiCl at concentrations ranging from 0.4 mmol/L to 2 mmol/L significantly inhibited the proliferation of HPP-CFC (P < 0.01), but concentrations ranging from 0.4 mmol/L to 1 mmol/L significantly increased the production of CFU-GM (P < 0.05), both effects displayed in dose-dependent manners. The different effects of LiCl on the proliferation of HPP-CFC and CFU-GM suggest that LiCl may induce HPP-CFC differentiation into more mature cells.

Simian virus 40 T antigen can regulate p53-mediated transcription independent of binding p53

A simian virus 40 (SV40) T-antigen mutant containing only the N-terminal 136 amino acids, able to bind to Rb and p300 but not p53, partially inhibited p53-mediated transcription without affecting the ability of p53 to bind DNA. These results suggest that SV40 T antigen can regulate p53-mediated transcription either directly through protein-protein association or indirectly through interaction with factors which may function to confer p53-mediated transcription.

[Elastic light scattering of blood cell counting and classification]

In this paper we discuss the elastic light scattering techniques used in blood cell counting and classification and expound the principles of elastic light scattering techniques and four theoretical scattering models of blood cell and the applicable areas. Also we analyze their application in recent years and point out the problems to be solved.

Responses of neurons in the inferior colliculus to binaural masking level difference stimuli measured by rate-versus-level functions

The psychophysical detection threshold of a low-frequency tone masked by broadband noise is reduced by < or = 15 dB by inversion of the tone in one ear (called the binaural masking level difference: BMLD). The contribution of 120 low-frequency neurons (best frequencies 168-2,090 Hz) in the inferior colliculus (ICC) of the guinea pig to binaural unmasking of 500-Hz tones masked by broadband noise was examined. We measured rate-level functions of the responses to identical signals (So) and noise (No) at the two ears (NoSo) and to identical noise but with the signal inverted at one ear (NoS pi): the noise was 7-15 dB suprathreshold. The masked threshold was estimated by the standard separation, "D". The neural BMLD was estimated as the difference between the masked thresholds for NoSo and NoS pi. The presence of So and S pi tones was indicated by discharge rate increases in 55.3% of neurons. In 36.4% of neurons, the presence of So tones was indicated by an increase in discharge rate and S pi tones by a decrease. In 6.8% of neurons, both So and S pi tones caused a decrease in discharge rate. In only 1.5% of neurons was So indicated by a decrease and S pi by an increase in discharge rate. Responses to the binaural configurations were consistent with the neuron's interaural delay sensitivities; 34.4% of neurons showing increases in discharge rate to both So and S pi tones gave positive BMLDs > or = 3 dB (S pi tones were detected at lower levels than So), whereas 37.3% gave negative BMLDs > or = 3 dB. For neurons in which So signals caused an increase in the discharge rate and S pi a decrease, 72.7% gave positive BMLDs > or = 3 dB and only 4.5% gave negative BMLDs > or = 3 dB. The results suggest that the responses of single ICC neurons are consistent with the psychophysical BMLDs for NoSo versus NoS pi at 500 Hz, and with current binaural interaction models based on coincidence detection. The neurons likely to contribute to the psychophysical BMLD are those with BFs near 500 Hz, but detection of So and S pi tones may depend on different populations of neurons.

Elevated expression of glutathione peroxidase in PC12 cells results in protection against methamphetamine but not MPTP toxicity

In vivo administration of either 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (MA) produces damage to the dopaminergic nervous system which may be due in part to the generation of reactive oxygen species (ROS). The resistance of superoxide dismutase (SOD) over-expressing transgenic mice to the effects of both MPTP and MA suggests the involvement of superoxide in the resulting neurotoxicity of both compounds. Superoxide can be converted by SOD to hydrogen peroxide, which itself can cause cellular degeneration by reacting with free iron to produce highly reactive hydroxyl radicals resulting in damage to proteins, nucleic acids and membrane phospholipids. Hydrogen peroxide has also been reported to be produced via inhibition of NADH dehydrogenase by MPP + formed during oxidation of MPTP by MAO-B and by dopamine auto-oxidation following MA-induced dopamine release from synaptic vesicles within nerve terminals. To test whether hydrogen peroxide is an important factor in the toxicity of either of these two neurotoxins, we created clonal PC12 lines expressing elevated levels of the hydrogen peroxide-reducing enzyme glutathione peroxidase (GSHPx). Elevation of GSHPx levels in PC12 was found to diminish the rise in ROS levels and lipid peroxidation resulting from MA but not MPTP treatment. Elevated levels of GSHPx also appeared to prevent decreases in transport-mediated dopamine uptake produced via MA administration as well as to attenuate toxin-induced cell loss as measured by either MTT reduction or LDH release. Our data, therefore, suggest that hydrogen peroxide production likely contributes to MA toxicity in dopaminergic neurons.

[Employing deconvolution method for correcting scatter in radiography]

It is well known that the scattered-radiation (SR) results in degradation of the images contrast in digital X-ray radiograph. The main reason affecting radiographic image quality is the SR arising from interaction of the photons with object being radiographed and veiling glare from detector system in the II-TV chai imaging system. With the aim of improving the image quality, we employed the Gaussian function to approximate the scattered point spread function (PSF) and determined the fraction of SR, rho and the parameter, sigma experimentally on an individual system; then we built an inverse filter to process the digital chest X-ray images, which were acquired with the same system and transformed in 2-D Fourier tansform operation. The images processed were corrected by using a variable weihting factor and the resulting images are shown in this paper. The method provides a useful way for solving the problem of correction of the SR in digital X-ray images.

Escherichia coli endonuclease VIII: cloning, sequencing, and overexpression of the nei structural gene and characterization of nei and nei nth mutants

Escherichia coli possesses two DNA glycosylase/apurinic lyase activities with overlapping substrate specificities, endonuclease III and endonuclease VIII, that recognize and remove oxidized pyrimidines from DNA. Endonuclease III is encoded by the nth gene. Endonuclease VIII has now been purified to apparent homogeneity, and the gene, nei, has been cloned by using reverse genetics. The gene nei is located at 16 min on the E. coli chromosome and encodes a 263-amino-acid protein which shows significant homology in the N-terminal and C-terminal regions to five bacterial Fpg proteins. A nei partial deletion replacement mutant was constructed, and deletion of nei was confirmed by genomic PCR, activity analysis, and Western blot analysis. nth nei double mutants were hypersensitive to ionizing radiation and hydrogen peroxide but not as sensitive as mutants devoid of base excision repair (xth nfo). Single nth mutants exhibited wild-type sensitivity to X rays, while nei mutants were consistently slightly more sensitive than the wild type. Double mutants lacking both endonucleases III and VIII exhibited a strong spontaneous mutator phenotype (about 20-fold) as determined by a rifampin forward mutation assay. In contrast to nth mutants, which showed a weak mutator phenotype, nei single mutants behaved as the wild type.

[Effects of lithium chloride and harringtonine on the differentiation, proliferation and c-myc proto-oncogene expression of HL-60 cells]

This research was to observe the effects of lithium chloride (LiCl) and Harringtonine (HT) on the proliferation and differentiation of HL-60 leukemia cells. The results obtained by liquid suspension culture, semi-solid colony culture and 3H-TdR incorporation into HL-60 cells indicated that different concentrations of LiCl (5-20 mmol/L) and HT (10(-8)-10(-5)mol/L) exerted the inhibitory effects in a dose-dependent manner on HL-60 cell proliferation respectively. When LiCl (10 mmol/L) and HT (10(-7) mol/L) were added together in the liquid culture or semi-solid culture of HL-60 cells, they showed much greater inhibitory effect than that by each agent separately. It was discovered that there was induction of the differentiation of HL-60 cells by lithium and HT and the induction of HL-60 cells differentiation by HT was markedly enhanced by the addition of low concentration of lithium. This work also showed that by treating HL-60 cells with lithium and HT, the expression of the c-myc proto-oncogene was markedly decreased as measured by RT/PCR-mRNA (P < 0.01). These findings provide some evidence of the mechanismcausing leukemic change and of the potential use of lithium and HT in the treatment of leukemia and in vitro purging of leukemic cells for autologous bone marrow transplantation.

[The development of a special instrument for measuring propagation velocity distribution of compound active potential using collision method]

This paper introduced a special instrument for measuring the propagation velocity distribution of compound active potential using collision method. In briefly, the principle of collision method is introduced. The structure and operation principle of the neuroelectrical amplifier, A/D converter and computer interface circuit are emphatically discussed. The instrument has the advantage of usable and low costing. It has considerable application value in clinical pathological diagnosis and research experiments of nervous system.

Innate control of the early course of infection in mice inoculated with Trypanosoma musculi

Infections of mice with Trypanosoma musculi result in marked suppression of acquired humoral immunity but rapid activation of splenic NK cell cytotoxicity. We show that both NK cells and activated peritoneal space (PS) macrophages (MP) participate in the innate immune control of T. musculi infections preceding escape of curative antibody production from suppression. Splenic NK cytotoxicity reaches a peak on Days 3-4 of infection and then rapidly declines. Rising cytotoxicity is paralleled by a rising number of NK cells. The decline in cytotoxicity occurs even though the number of splenic NK cells continues to rise. The critical role of NK cells in the control of the early course of T. musculi infection was demonstrated by the effects of either depleting NK cells (antiasialo GM1 treatment) or maintaining them in an activated state (poly(I:C) injections). The importance of MP in controlling the infection was suggested by studies involving proteose peptone elicited MP both in vivo and in culture. The results presented here strongly suggest that innate immunity involving NK cells and MP can control, but not cure, T. musculi infections. Whether this early innate response influences the subsequent acquired, curative response remains to be studied. Detailed analyses of innate immunity in this experimental infection should suggest new approaches to intervention in early pathogenic infections.

Changes of plasma tPA and PAI activities in patients with diabetic retinopathy

PURPOSE

To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI).

METHODS

tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked fashion.

RESULTS

1. tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P < 0.001); 2. tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non-DR (NDR) and background-DR (BDR) subgroups (P < 0.01, respectively); 3. there was no significant difference between BDR and NDR subgroups (P > 0.05); and 4. the results also suggested that the severity of DR and duration of diabetes were correlated negatively with the activity of tPA but positively with that of PAI (r = -0.564, -0.416, 0.671, 0.442; P < 0.01, respectively).

CONCLUSIONS

Reduced plasma tPA activity and enhanced PAI activity in diabetic patients, probably is one of the causes for thromboembolic diseases and are related to the severity of DR and duration of diabetes. Therefore, the change and imbalance between activities of plasma tPA and PAI might play a role in developing and progression of DR.

[Applying correlation dimension of R-R intervals to the analysis of heart rate variability]

This paper addresses the correlation dimension of R-R intervals under Heart Rate Variability (HRV) conditions according to chaos theory. We calculate the R-R interval dimensions of normal people's waking and sleeping status, and of different status of a 24-hour clinical Holter recording. The results show that the bigger the HRV is, the smaller the dimension of R-R interval is. This method needs small data and costs little time to calculate, so probably it can be of clinical use in the analysis of HRV.

[A fast iterative algorithm for adaptive histogram equalization]

In this paper, we propose an iterative algorthm called FAHE., which is based on the relativity between the current local histogram and the one before the sliding window moving. Comparing with the basic AHE, the computing time of FAHE is decreased from 5 hours to 4 minutes on a 486dx/33 compatible computer, when using a 65 x 65 sliding window for a 512 x 512 with 8 bits gray-level range.

[Experimental study prevention of reperfusion injury of skeletal muscle by local hypothermia and its clinical application]

Local hypothermia as a preventive method to reperfusion injury of skeletal muscles was studied. Sixteen Japanese rabbits were divided into four groups at random. Before the tourniquet was inflated, a cold gel pack was applied to the right hind leg of each rabbit for 15 minutes to produce local hypothermic condition, without application of tourniquet the left hind limb was under local hypothermic condition as a control. The duration of tourniquet ischemia was 4 hours, and then reperfusion for one and two hours in the A and B groups respectively; in the C and D groups the duration of ischemia was 5 hours, and reperfusion for one and two hours, respectively. The muscle temperature averaged 16.6 degrees C with a needle thermocouple in the hind limb under local hypothermia. The serum K+, LA, SOD, LPO were determined from bilateral femoral veins, and electron and light microscopic studies of sural muscles were done in the post-reperfusion period. It was found that the K+, LA, LPO were lower than that of the control groups (P < 0.01), but SOD was higher than that of the control group (P < 0.01). Electron and light microscopic studies showed sight but reversible damage of muscular structure with the possibility of in the hypothermic groups cell regeneration. Basing on this experimental results, this method was applied in 45 cases reparative and reconstructive surgery of limbs. The duration of application of tourniquet averaged 2 hours and 57 minutes, the longest being 4 hours and 31 minutes, when the muscle temperature had reduced to 22.4 degrees C. There were no postoperative complications associated with this technique. Local hypothermia appeared to be a safe and effective method of decreasing the reperfusion damage after ischemia.

Interaural delay sensitivity and the classification of low best-frequency binaural responses in the inferior colliculus of the guinea pig

Monaural and binaural response properties of single units in the inferior colliculus (IC) of the guinea pig were investigated. Neurones were classified according to the effect of monaural stimulation of either ear alone and the effect of binaural stimulation. The majority (309/334) of IC units were excited (E) by stimulation of the contralateral ear, of which 41% (127/309) were also excited by monaural ipsilateral stimulation (EE), and the remainder (182/309) were unresponsive to monaural ipsilateral stimulation (EO). For units with best frequencies (BF) up to 3 kHz, similar proportions of EE and EO units were observed. Above 3 kHz, however, significantly more EO than EE units were observed. Units were also classified as either facilitated (F), suppressed (S), or unaffected (O) by binaural stimulation. More EO than EE units were suppressed or unaffected by binaural stimulation, and more EE than EO units were facilitated. There were more EO/S units above 1.5 kHz than below. Binaural beats were used to examine the interaural delay sensitivity of low-BF (BF < 1.5 kHz) units. The distributions of preferred interaural phases and, by extension, interaural delays, resembled those seen in other species, and those obtained using static interaural delays in the IC of the guinea pig. Units with best phase (BP) angles closer to zero generally showed binaural facilitation, whilst those with larger BPs generally showed binaural suppression. The classification of units based upon binaural stimulation with BF tones was consistent with their interaural-delay sensitivity. Characteristic delays (CD) were examined for 96 low-BF units. A clear relationship between BF and CD was observed. CDs of units with very low BFs (< 200 Hz) were long and positive, becoming progressively shorter as BF increased until, for units with BFs between 400 and 800 Hz, the majority of CDs were negative. Above 800 Hz, both positive and negative CDs were observed. A relationship between CD and characteristic phase (CP) was also observed, with CPs increasing in value as CDs became more negative. These results demonstrate that binaural processing in the guinea pig at low frequencies is similar to that reported in all other species studied. However, the dependence of CD on BF would suggest that the delay line system that sets up the interaural-delay sensitivity in the lower brainstem varies across frequency as well as within each frequency band.

Binaural masking level differences in the inferior colliculus of the guinea pig

The binaural masking level difference (BMLD) is a striking and well-documented psychophysical effect which relates to the ability to use the phase of low-frequency sounds to dissociate them from masking noise. When identical tones and noise are presented to both ears, detectability is improved by up to 15 dB simply by inverting the phase of either the tone or noise in one ear. Measurements of BMLDs were made in single delay-sensitive neurones in the inferior colliculus of the guinea pig. These have confirmed and extended an earlier report [D. M. Caird, A. R. Palmer, and A. Rees, Hear. Res. 57, 91-106 (1991)] by demonstrating that when signals are optimized for the frequency, level, and interaural delay sensitivities of each neurone, BMLDs can be measured which are in a direction, and of a magnitude, consistent with appropriate psychophysical observations in human subjects. In addition, BMLDs were found to be consistent with the delay sensitivities of the neurones to the signal and masker, the major determinant of the masked threshold for optimized signals being the activity evoked in the neurone by the masking noise. Within-channel signal-to-noise (S/N) ratios at masked threshold for single neurones varied from +20 to -7 dB, depending on the binaural configuration and the units' delay sensitivities. In single neurones, the size of the BMLD for optimized signals increased with the level of the noise. The BMLD increased by 5 dB over a 40-dB range of noise, consistent with psychophysical observations. This came about because as noise level increased, masked threshold for optimized tones increased more slowly in Npi noise than in N0 noise. For all binaural comparisons, both positive (pi signals more detectable, as in the psychophysics) and negative BMLDs were observed, often in the same neurone, a result entirely consistent with the sensitivity to the interaural delay of the noise and tone signals. For 500-Hz signals in zero and pi phase masked by identical noise the majority of BMLDs determined with the PEST procedure was negative, a result which is taken to indicate that increases in spike rate may not be an appropriate cue for masked threshold under these conditions.

[A study on the course of corneal epithelial healing in diabetic rabbits]

OBJECTIVE

In order to approach the course of corneal epithelial healing of diabetes mellitus.

METHODS

The experimental rabbit diabetes models were produced by the injection of alloxan. The corneal epithelium of each rabbit was removed by freezing with a 6 mm diameter brass probe cooled in liquid nitrogen. The rate of corneal epithelial healing following freezing in the normal rabbit was compared to that in the diabetic one. Contrasted with the normal rabbits, the ultrastructural changes of the epithelium with and without freezing were also observed in the diabetic rabbits.

RESULTS

It is shown that there is no statistical significant difference in the overall rate of epithelial healing between the normal and diabetic rabbit. In contrast with the normal rabbit, the epithelial basement membrane of the diabetic rabbit without freezing revealed markedly thickened, and the mitochondria and glycogen particles in the epithelial cell increased. In the diabetic rabbit with freezing, the epithelial basement membrane appeared absent or discontinuous. After complete healing, the corneal epithelium was edematous in diabetic rabbit.

CONCLUSION

The abnormal basemenet membrane and edematous epithelial cell were responsible for the diabetic corneal epithelial poor healing and recurrent erosion.

p53 prevents maturation to the CD4+CD8+ stage of thymocyte differentiation in the absence of T cell receptor rearrangement

Rearrangement of the immunoglobulin (Ig) and T cell receptor (TCR) gene loci allows for the generation of B and T lymphocytes with antigen-specific receptors. Complete rearrangement and expression of the TCR-beta chain enables immature thymocytes to differentiate from the CD4-CD8- to the CD4+CD8+ stage mice in which rearrangement is impaired, such as severe combined immunodeficient (SCID) mice or recombinase activating gene-deficient (RAG-/-) mice, lack mature B and T lymphocytes. Thymocytes from these mice are arrested at the CD4-CD8- stage of T cell development. We previously observed that thymocytes from RAG-2-/- mice exposed to gamma radiation differentiate from CD4-CD8- into CD4+CD8+ without TCR-beta chain rearrangement. We now report that irradiated RAG-2-/- thymocytes undergo direct somatic mutations at the p53 gene locus, and that p53 inactivation is associated with maturation of RAG2-/- thymocytes to the CD4+CD8+ stage. Generation of RAG2-/- and p53-/- double-deficient mice revealed that, in the absence of TCR-beta chain rearrangement, loss of p53 function is sufficient for CD4-CD8- thymocytes to differentiate into the CD4+CD8+ stage of T cell development. Our data provide evidence for a novel p53 mediated checkpoint in early thymocyte development that regulates the transition of CD4-CD8- into CD4+CD8+ thymocytes.

Responses of ventral cochlear nucleus onset and chopper units as a function of signal bandwidth

1. The responses of units in the ventral cochlear nucleus in anesthetized guinea pigs have been measured to best-frequency tones, noise bands geometrically centered around the unit best frequency, and noise bands asymmetrically positioned around the best frequency. 2. Each unit isolated was characterized using peristimulus time histograms (PSTHs) to best-frequency tones at 20 and 50 dB suprathreshold, frequency-intensity response areas and rate-versus-level functions in response to best-frequency tones and wideband noise. The data reported here are derived from full analyses of 5 chopper units and 17 onset units. The onsets were divided into onset-I (OnI), onset-L (OnL), and onset-C (OnC) by the criteria described by Winter and Palmer: the PSTHs of OnI units show only an onset response, OnL units respond with a single spike at onset followed by a low level of sustained activity, and OnC units have PSTHs with one to four onset peaks and low levels of sustained discharge. 3. In response to geometrically centered noise bands of constant spectral density, the discharge of chopper units and one OnI unit increased over a relatively narrow range of bandwidths, corresponding to the equivalent rectangular bandwidth calculated from their response area, and then became constant. In contrast, OnL and OnC units showed increases in discharge rate with noise bandwidth over very wide ranges of bandwidth. The growth of the discharge rate with noise bandwidth was approximately linear on double logarithmic axes and therefore could be described by a power function with an exponent of 0.37. This relation held even for noise levels near threshold. 4. When noise bands with constant spectral density (at the input to the earphone) were presented with one edge fixed at the unit's best frequency, the discharge rate of most chopper units and the one OnI unit increased over a narrow range of bandwidths and then became constant. This pattern was observed irrespective of whether the second edge of the noise was progressively increased above, or decreased below, the best frequency. For two of the chopper units, in which lateral inhibitory sidebands could be demonstrated, increasing the noise bandwidth led first to increases and then to decreases in the discharge rate as the noise energy impinged upon the sideband. The chopper units act like energy detectors with a filter corresponding to their single tone response area, but, for some units, with the addition of inhibitory sidebands. 5. For the OnL and OnC units, increasing the noise bandwidth above or below best frequency caused progressive increases in the discharge rate over wide ranges of bandwidth. These increases occurred even for low noise spectral densities. The growth in discharge rate for these onset units was well fitted at all spectral density levels by power functions: one above best frequency and one below. At levels of the noise 40 dB above the unit threshold, the point at which the discharge rate reached 90% of its maximum was, on average, about 2 octaves below best frequency and 1 octave above. For some onset units, changes in the discharge rate were seen as the noise bandwidth was varied over about 14 kHz, which is about one-third of the total frequency hearing range of the guinea pig. 6. The data for onset units is consistent with the hypothesis that onset units in the ventral cochlear nucleus achieve their precision in the temporal domain by integration of the inputs from auditory nerve fibers with a wide range of best frequencies. The range of frequency over which onset units integrate frequency matches that of the inhibitory input to dorsal cochlear nucleus neurons, suggesting a possible role as an inhibitory interneuron.

Frequency extent of two-tone facilitation in onset units in the ventral cochlear nucleus

1. The frequency threshold curves (FTCs) of 91 single units in the cochlear nucleus of the anesthetized guinea pig were measured using a conventional single-tone paradigm and a two-tone paradigm designed to elucidate the frequency extent of two-tone facilitation in onset units (On). Units were classified according to existing classification schemes into primary-like (n = 3), chopper (n = 23), and three onset groups: OnI (n = 12), OnC (n = 29), and OnL (n = 24). Histological reconstructions show onset units to be widely distributed within the ventral cochlear nucleus in a manner generally consistent with its tonotopic organization. 2. The FTCs of onset units differed in their minimum thresholds, the steepness of their high- and low-frequency cutoffs, and their sharpness of tuning as quantified by the quality factor at 10 dB (Q10dB) above best frequency (BF) threshold values. There was considerable overlap in the sharpness of tuning between onset units and auditory nerve fibers, as indicated by the distribution of Q10dB values in the octave around 10 kHz: onset units had Q10dB values of 3.56 +/- 1.38 (SD), compared with 6.3 +/- 2.48 for auditory nerve fibers. The tuning of chopper units was similar to that of auditory nerve fibers (5.52 +/- 1.46). 3. Seventy-five percent of onset units showed some degree of facilitation (a threshold reduction) when their FTCs were measured in the presence of BF tones 4 dB below BF threshold. The frequency extent of such facilitation was variable, with a maximum of 6 octaves around the BF. In extreme cases facilitation could be measured when the BF tone was as low as 30 dB below BF threshold. 4. In 17% of onset units, suppressive effects were evident, as shown by noncontiguous frequency regions of facilitation. These suppressive effects might be a reflection either of suppression in the auditory nerve input or of a direct inhibitory input to the onset units. The strength of this effect suggests that inhibition is a likely explanation, consistent with the finding in previous morphological studies of profuse synapses with pleomorphic vesicles on multipolar cells. 5. FTCs of chopper and primary-like units measured in the presence of BF tones showed little facilitation. The facilitation that was observed in chopper units was confined to a narrow region around BF and disappeared when the facilitatory tone was lowered to 4 dB below BF threshold. 6. These data support the hypothesis that onset units, but not chopper or primary-like units, receive excitatory inputs from auditory nerve fibers with a wide range of BFs. However, the frequency range of facilitation and the magnitude of the threshold facilitation varied from unit to unit, suggesting that the off-BF inputs from auditory nerve fibers are not evenly distributed or equally effective in all units.

Requirement for TNF-alpha and IL-1 alpha in fetal thymocyte commitment and differentiation

CD25 expression occurs early in thymocyte differentiation. The mechanism of induction of CD25 before T cell receptor rearrangement and the importance of this mechanism for T cell development are unknown. In a thymus reconstitution assay, tumor necrosis factor alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha), two cytokines produced within the thymic microenvironment, induced CD25 expression on early immature thymocytes. Either TNF-alpha or IL-1 alpha was necessary for further thymocyte maturation and CD4+CD8+ differentiation. In irradiated mice reconstituted with CD117+CD25+ thymocytes, commitment to the T cell lineage was marked by the loss of precursor multipotency.

[The significance of high-density lipoprotein subfractions and triglycerides in predicting coronary artery disease]

Serum Lipid profiles, including high-density lipoprotein (HDL) and its subfractions HDL2 and HDL3 were obtained in 78 cases undergoing coronary angiography. Coronary artery disease (CAD) was present in 51 patients and absent in 27. We used a scoring methold of CAD to reflect the extent or narrowing of coronary artery. The largest difference between the two groups was observed in HDL2 Cholesterol with a mean of 0.37 mmol/L in patients with CAD as compared with 0.49 mmol/L in normal subjects (P < 0.001) and in TG (1.85 mmol/L vs 1.16 mmol/L) as well. Smaller difference was found in TC (5.9 mmol/L vs 4.87 mmol/L, P < 0.05). No singnificant difference was found in serum HDL (P > 0.05). Multivariate regression analysis revealed that the most powerful indenpendent variable associated with the extent of CAD was HDL2 cholesterol and triglyceride. The score of CAD was significantly correlated with HDL2-c (r = 0.32 P < 0.01) and TG (r = 0.34 P < 0.01). It is shown that high serum level of TG (> 1.6 mmol/L) and low serum level of HDLC2 (< 0.37 mmol/L) were the strengest predictors of presence and extent of CAD.

Caloric restriction: conservation of in vivo cellular replicative capacity accompanies life-span extension in mice

In male mice of a long-lived hybrid strain (B6D2F1), long-term 40% caloric restriction (CR) extended both mean and maximum life spans by 36 and 20%, respectively, over that of ad libitum fed (AL) controls. Measurements of entry into S-phase were made in vivo of six different cell types in five different organs using 2-week exposures to BrdU. The labeling index (L.I.) in all organs studied was lower in young CR mice than in young AL fed mice. In most cases, the L.I. in AL mice fell to the levels of that in the CR mice by 13 months of age, and the two groups then remained so through old age. However, when the L.I. was measured in old CR mice which had been placed on the AL diet for a period of 4 weeks (this was termed refeeding (RF), it was found to be above that of similar age AL or CR mice and almost at the level of young AL mice. This was still true, but to a lesser degree, in a repeat study using an 8-week period of RF. In a separate but parallel in vitro study (companion paper, this volume), the superiority of CR over AL for retention of cellular replication capacity was confirmed by clone size distribution measurements made in several cell types in mice of several age groups. These results indicate that: (1) the rate of cell replication in AL diet mice diminishes greatly by early middle age in all organ sites studied and then plateaus or declines much more slowly; (2) CR broadly preserves in vivo cellular replicative capacity but often requires the energy levels provided by a switch to AL feeding to demonstrate this late in life; (3) accordingly, the replicative deficit in AL fed mice appears to be cumulative and is significant only in old age. The mechanism(s) involved is yet to be discovered but may be related to, or even the same as, that which extends life spans in CR animals. Correspondingly, and with corroborative data from our in vitro companion study, (W. R. Pendergrass et al., 1995. Exp. Cell. Res. 217, 309-316), we suggest that cell populations sustain an accrual of biochemical damage or physiological alterations which increasingly limit their replicative capacity as the animal ages, and that CR reduces the accrual of this damage.

Caloric restriction: conservation of cellular replicative capacity in vitro accompanies life-span extension in mice

We have tested whether life-long caloric restriction (CR) slows or delays the age-related loss of cellular replicative potential that occurs during normal aging in ad libitum (AL) fed mice. Both mean and maximum life spans of the restricted animals (60% of AL intake) were significantly extended 30-40% by CR treatment. Proliferative potential, measured by determining the fraction of cells capable of forming large clones in vitro, was compared in five cell types from six tissue sites from two strains of mice (Male (C57BL/6 x DBA/2)F1("B6D2F1") and female (C57BL/6 x C3H)F1("B6C3F1")). This included four nonhematopoietic organ sites: fibroblast cells from ear skin, tail skin, and subdermal connective tissue and epithelial cells from the medullary part of the kidney and two cell types, myofibroblasts and endothelial-like cells, from spleen and bone marrow. The proliferative potential of cells from AL mice decreased progressively with age in all tissues sites of both mouse strains. CR delayed or decreased the loss of proliferative potential in all situations, but the timing of this was tissue specific. For cells from the four nonhematopoietic tissues sites from female B6C3F1 female mice, CR delayed the onset of proliferative loss, such that the fraction of large clones was significantly greater for the CR 18- to 24-month-old mice than in AL controls at three of four sites (as determined by the fraction of large clones after 1 week of clonal growth). The proliferative loss in CR tissues then accelerated from 24 to 30 months, so that both CR and AL mice had similar fractions of large clones after 30 months of age. CR was also seen to delay loss of proliferative potential in cells from skin and kidney of B6D2F1 male mice at 23-24 months of age when cloned for 2 weeks. For fibroblast and endothelial-like cells from bone marrow and spleen stromal sites from both strains of mice, CR also significantly decreased loss of proliferative potential; furthermore, in these tissues the proliferative advantages remained or increased from 24 to over 30 months of age. In companion studies (N.S. Wolf et al., 1995. Exp. Cell. Res. 217, 000-000), CR was seen to decrease age-related losses in the maximal rates of cell replication in vivo in a panel of tissues from B6D2F1 male mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Developmental hematopoiesis from prenatal to young-adult life in the mouse model

Five measurements of hematopoietic function were made in the mouse from midfetal life to young adulthood. These included two in vivo (day-8 colony-forming unit-spleen [CFU-S8] and day-12 CFU-S [CFU-S12]) and two in vitro clonal measurements of hematopoietic stem and progenitor cells (high proliferative potential colony-forming cell [HPP-CFC] and CFC of low proliferative potential [LPP-CFC]) as well as an in vitro clonal measurement of colony-forming unit-fibroblast (CFU-F). The appearance, increase, subsequent decrease, and later emergence and increase of each of these parameters in the fetal-liver, newborn, growing-infant, and young-adult bone marrow were correlated and found to be in parallel. Exceptions to this included the earlier appearance in the fetal liver of CFU-F and the relatively differentiated hematopoietic LPP-CFC. The pattern of emergence of these progenitor cell subpopulations in the fetal liver may be related, in part to the timing of the hematopoietic microenvironment development and the relative frequencies of progenitor cell types in the circulation. This developmental study in the mouse model describes additional correlations between in vivo and in vitro colony-forming stem cells and fibroblastic stromal colony-forming cells, and it suggests the dependence of hematopoietic stem cells upon the stromal microenvironment for the necessary conditions for hematopoietic stem cell lodgment, growth, and maturation.

Sublethal gamma-radiation induces differentiation of CD4-/CD8- into CD4+/CD8+ thymocytes without T cell receptor beta rearrangement in recombinase activation gene 2-/- mice

DNA recombination of the immunoglobulin (Ig) or T cell receptor (TCR) gene loci is an essential step in the production of lymphocytes bearing antigen-specific receptors. Mice that lack the ability to rearrange their Ig and TCR gene loci are devoid of mature B and T cells. Complete rearrangement and expression of the TCR-beta chain has been suggested to allow immature thymocytes to switch from the CD4-/CD8- to the CD4+/CD8+ stage of thymic development. Thus, thymocytes from severe combined immune deficient (SCID) mice or mice deficient in recombinase activation genes (RAG), which do not undergo proper DNA rearrangement, are arrested at the early CD4-/CD8- stage of development. B cell precursors in SCID or RAG mice do not progress from the B220+/sIgM-/heat stable antigen (HSA)+/CD43+ to the B220+/sIgM-/HSA+/CD43- stage. In an attempt to reconstitute RAG-2-/- mice with bone marrow- or fetal liver-derived progenitor cells, we subjected these mice to sublethal doses of gamma-radiation. It is surprising that in the absence of donor cells, irradiated RAG-2-/- mice revealed a dramatic change in their lymphoid phenotype. 14 d after irradiation, the majority of thymocytes had advanced to the CD4+/CD8+ stage of T cell development and a small number of bone marrow precursors had progressed to the CD43-, HSAhi stage of B cell development. Analysis of the resulting CD4+/CD8+ thymocytes revealed no surface expression of the TCR/CD3 complex and no V-D-J rearrangement of the TCR-beta gene locus. Our findings provide evidence for a novel pathway that allows the transition of thymocytes from the CD4-/CD8- to the CD4+/CD8+ stage and that does not appear to require TCR-beta chain rearrangement.