Presumed inhibitory neurons in the macaque inferior temporal cortex: visual response properties and functional interactions with adjacent neurons

Neurons in area TE of the monkey inferior temporal cortex respond selectively to images of particular objects or their characteristic visual features. The mechanism of generation of the stimulus selectivity, however, is largely unknown. This study addresses the role of inhibitory TE neurons in this process by examining their visual response properties and interactions with adjacent target neurons. We applied cross-correlation analysis to spike trains simultaneously recorded from pairs of adjacent neurons in anesthetized macaques. Neurons whose activity preceded a decrease in activity from their partner were presumed to be inhibitory neurons. Excitatory neurons were also identified as the source neuron of excitatory linkage as evidenced by a sharp peak displaced from the 0-ms bin in cross-correlograms. Most inhibitory neurons responded to a variety of visual stimuli in our stimulus set, which consisted of several dozen geometrical figures and photographs of objects, with a clear stimulus preference. On average, 10% of the stimuli increased firing rates of the inhibitory neurons. Both excitatory and inhibitory neurons exhibited a similar degree of stimulus selectivity. Although inhibitory neurons occasionally shared the most preferred stimuli with their target neurons, overall stimulus preferences were less similar between adjacent neurons with inhibitory linkages than adjacent neurons with common inputs and/or excitatory linkages. These results suggest that inhibitory neurons in area TE are activated selectively and exert stimulus-specific inhibition on adjacent neurons, contributing to shaping of stimulus selectivity of TE neurons.     

Effective in vitro clearance of Porphyromonas gingivalis by Fc alpha receptor I (CD89) on gingival crevicular neutrophils

Porphyromonas gingivalis has been implicated as a causative pathogen in periodontitis. Immunotherapeutic approaches have recently been suggested to aid in the clearance of P. gingivalis from disease sites. Because antibody-Fc receptor (FcR) interactions play a role in the effector functions of polymorphonuclear neutrophils (PMN), we evaluated which FcR on PMN from gingival crevicular fluid (GCF) serves as an optimal target molecule for FcR-directed immunotherapy. GCF PMN and peripheral blood (PB) PMN from adult periodontitis patients were analyzed for their immunoglobulin G (IgG) and IgA FcR (Fc gamma R and Fc alpha R, respectively) expression and function by studying IgG- and IgA-mediated elimination of P. gingivalis. GCF PMN exhibited higher Fc alpha RI and Fc gamma RI levels and lower Fc gamma RIIa and Fc gamma RIIIb levels than PB PMN. Functional studies revealed that GCF PMN exhibited less of a capacity to phagocytose and kill IgG1-opsonized P. gingivalis than PB PMN. IgA1-mediated phagocytosis and killing capacity was, however, comparable between GCF PMN and PB PMN. In summary, these in vitro results document that Fc alpha RI represents a candidate target for FcR-directed immunotherapy for the clearance of P. gingivalis.     

Epidemiological Analysis of Salmonella enteritidis Isolates from Humans and Broiler Chickens in Thailand by Phage Typing and Pulsed-Field Gel Electrophoresis

To determine the phage types (PT) of Salmonella enteritidis found in Thailand and to clarify the potential for human infection by S. enteritidis in broiler chicken meat, human and poultry isolates taken from Thailand between 1990 and 1997 were phage typed and analyzed by pulsed-field gel electrophoresis (PFGE). Ten different PT were found among the 302 isolates phage typed, with PT 4 being the most frequent in human (73.9%) and poultry (76.2%) isolates, followed by PT 1 (8.0%), 8 (3.6%), and 7a (2.2%) in human isolates and by PT 7a (4.9%), 1 (3.7%), and 12 (2.4%) in poultry isolates. Of the 53 isolates analyzed by PFGE, 45 showed an indistinguishable pattern (pattern A) by BlnI-digested PFGE and the other 8 isolates showed a very similar pattern that differed by only a few bands. These results indicate the spread of a genetically identical clone of S. enteritidis in humans and poultry in Thailand.     

BRONCHIAL CARCINOID ACCOMPANIED BY THYROID ADENOMAS AND ADRENAL ADENOMAS

A large tumor massively occupying the left pleural cavity had the Andings of both typical carcinoid and oncocytoma which were thought to be of bronchogenic origin. The ultrastructural observation of the tumor revealed a mixture of rod-shaped granules in addition to usual round neurosecretory ones. In the nuclei of dark cells of the oncocytoma, a latticed or hatched structure was detected. Besides two adenomas and hyperplastic foci of large acidophilic cells in the thyroid, a black adenoma and cortical adenoma in the adrenal gland, were detected. Moreover, there was an ectopic adrenal gland in the retroperitoneum. Briefly it was suggested that the bronchial carcinoid presented may be related to multiple endocrine adenomatosis.     

IMMUNOHISTOCHEMICAL DEMONSTRATION OF PEPTIDE YY IN GASTROINTESTINAL ENDOCRINE TUMORS

Fourteen cases of gastrointestinal endocrine tumors were examined im-munohistochemically for peptide YY, pancreatic polypeptide, glucagon, and somatostatin. Peptide YY cells were present in seven tumors, pancreatic polypeptide cells in eight tumors, glucagon cells in six tumors, and somatostatin cells in nine tumors. All 7 rectal endocrine tumors examined were found to contain peptide YY, while in the tumors of the other sites peptide YY cells were not detected. Peptide YY cell population in the rectal tumors was small to moderate in comparison with pancreatic polypeptide and glucagon cell population. This study suggests that peptide YY cells may be a common constituent of rectal endocrine tumors together with pancreatic polypeptide and glucagon cells, and that the peptide YY spectrum of gastrointestinal endocrine tumors may be closely related to the location of the tumors. Moreover, it can also be said that peptide YY may be used as one of the markers of rectal endocrine tumors.     

Receptive field organization of bipolar and amacrine cells in the goldfish retina

1. Intracellular recordings were made from bipolar and amacrine cells in the isolated goldfish retina. Cells were identified mainly from their response patterns to a spot and an annulus in reference to the knowledge obtained from the previous work of intracellular Procion Yellow injection. Using white light and monochromatic lights receptive field organization of recorded cells were analysed.2. All bipolar cells had a centre-surround organization in their receptive fields. The field centre was estimated to be 100-200 mum in diameter, and the surround 1-1.5 mm.3. Bipolar cells were classified into two types according to the response properties to monochromatic lights. Opponent colour cells received inputs from red and green cones, responding with red on-centre, red and green off-surround or vice versa. Cells without colour coding received input from red cones both in the field centre and the surround. In these cells the centre and the surround were well balanced.4. Amacrine cells were also classified into two types, a sustained type and a transient type. The sustained type amacrine cells responded with a steady potential change and were colour coded. They were hyperpolarized by red and depolarized by green light. The transient type amacrine cells responded with transient depolarization at on and off of light flashes. They received input chiefly from red cones and were not colour coded. Both types of amacrine cells showed a large spatial summation in an area over 2.5 mm; centre-surround antagonism was not seen.5. Comparing the size of the receptive field with anatomy, especially with the size of dendritic spread, the field centre of bipolar cells agreed in size with their dendritic spread. Bipolar cell surround clearly exceeded its dendritic field. Since the response properties of the bipolar cell surround was mimicked most closely by the receptive field of external horizontal cells, the input to the bipolar cell surround is thought to be mediated by external horizontal cells.6. By comparing receptive field properties of various retinal cells it is suggested that both the opponent colour bipolar cells and the colour coded amacrine cells converge on to the double opponent ganglion cells.     

Morphology of equine allantochorion at the tip of the pregnant horn

The morphology of the equine allantochorion at the tip of the pregnant horn was studied in the membranes of 14 mares. The findings in the allantochorion at the tip of the pregnant horn were of two types; one was growth retardation (hypoplastic villi, tunica adventitia of the vessels resembling embryonal connective tissue and the extended spaces of remnants of the extraembryonic coelom), the other was placental hypoxia or ischaemia (parakeratosis, stratified squamous metaplasia, necrosis of the trophoblasts, thickening of the basement membrane and fibrous hyperplasia of villous stroma). It seems likely that hypoplastic villi are caused by disordered formation of the microcotyledon accompanying the progression of pregnancy.     

Effect of ethanol treatment on metabolic activation and detoxification of esophagus carcinogenic N-nitrosamines in rat liver

In order to elucidate the mechanism underlying enhancement by ethanol of N-nitrosodiethylamine (DEN)- and N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumorigenesis in rats, hepatic levels of cytochrome P-450 (CYP) enzymes, mutagenic activation of several N-nitrosamines and three kinds of UDP-glucuronyltransferase (UDPGT) activities were assayed in F344 rats. Immunoblot analyses of microsomal CYP proteins revealed induction of CYP2E1 (approximately 2-fold), but not CYP2B1/2, 1A1/2 or 3A2, by treatment with 10% ethanol in the drinking water for 2 weeks. In contrast, s.c. treatment with 0.5 mg/kg NMBA three times per week for 2 weeks produced no significant alterations in the levels of these CYP species. Ethanol treatment also elevated the mutagenic activities of N-nitrosodimethylamine (DMN), DEN and N-nitrosopyrrolidine (NPYR) in strain TA100 up to 2.1-, 1.6- and 2.3-fold above each control, respectively. However, this was not the cases for four N-nitrosamines, including NMBA, in strain TA100 and two heterocyclic amines and aflatoxin B(1) in strain TA98. In addition, ethanol did not affect UDPGT activities towards 4-nitrophenol, bilirubin and testosterone. Hepatic CYP species responsible for mutagenic activation of selected N-nitrosodialkylamines were confirmed by use of specific CYP inducers and inhibitors with the liver from F344 and Wistar rats, indicating that DMN, DEN and NMBA are selectively activated by CYP2E1, predominantly by CYP2E1 with a slight contribution by CYP2B2 and selectively by CYP2B1/2, respectively. These results demonstrate that ethanol exerts an enhancing effect on mutagenic activation by CYP2E1 of DMN, DEN and NPYR, but does not affect that of NMBA and the other carcinogens by CYP2B1/2, 1A1/2 and 3A2 and UDPGT1A1, 1A6 and 2B1 activities. Consequently, this suggests that enhancement by ethanol of DEN-induced esophageal carcinogenesis in F344 rats can be attributed to an increase in hepatic activation during the initiation phase, but that of NMBA-induced tumorigenesis is not attributable to metabolic activation and inactivation via glucuronidation in liver.     

Twenty-six-Week carcinogenicity study of chloroform in CB6F1 rasH2-transgenic mice

The carcinogenic potential of chloroform was evaluated in a short-term carcinogenicity testing system using CB6F1 rasH2-Tg (rasH2-Tg) mice. Chloroform was administered to rasH2-Tg males at doses of 28, 90, or 140 mg/kg and rasH2-Tg females at 24, 90, or 240 mg/kg by oral gavage for 26 weeks. Wild-type (non-Tg) male and female mice received doses of 140 mg/kg and 240 mg/kg, respectively. N-methyl-N-nitrosourea was administered to rasH2-Tg mice by single intraperitoneal injection (75 mg/kg) as a positive control. In both the rasH2-Tg and non-Tg mice, there was no significant increase in the incidence of neoplastic lesions by chloroform treatment. The incidence of hepatocellular foci in the rasH2- and non-Tg females receiving 240 mg/kg was increased. Forestomach tumors and malignant tumors occurred in most of the rasH2-mice in the positive control group. Swelling or vacuolation of hepatocytes, a toxic change induced by chloroform, occurred in both the rasH2-Tg and non-Tg mice. It is concluded that chloroform, a putative human noncarcinogen, did not show evidence of carcinogenic potential in the present study using rasH2-Tg mice. This study suggests that the rasH2-Tg mouse model may not be appropriate for detecting nongenotoxic carcinogens. However, the sensitivity of rasH2-Tg mice to nongenotoxic carcinogens should be assessed with consideration of the results from the other ILSI-HESI project studies.