Columns for visual features of objects in monkey inferotemporal cortex

At early stages of the mammalian visual cortex, neurons with similar stimulus selectivities are vertically arrayed through the thickness of the cortical sheet and clustered in patches or bands across the surface. This organization, referred to as a 'column', has been found with respect to one-dimensional stimulus parameters such as orientation of stimulus contours, eye dominance of visual inputs, and direction of stimulus motion. It is unclear, however, whether information with extremely high dimensions, such as visual shape, is organized in a similar columnar fashion or in a different manner in the brain. Here we report that the anterior inferotemporal area of the monkey cortex, the final station of the visual cortical stream crucial for object recognition, consists of columns, each containing cells responsive to similar visual features of objects.

Translocation of SAPK/JNK to mitochondria and interaction with Bcl-x(L) in response to DNA damage

Activation of the stress-activated protein kinase (SAPK/JNK) by genotoxic agents is necessary for induction of apoptosis. We report here that ionizing radiation ionizing radiation exposure induces translocation of SAPK to mitochondria and association of SAPK with the anti-apoptotic Bcl-x(L) protein. SAPK phosphorylates Bcl-x(L) on threonine 47 (Thr-47) and threonine 115 (Thr-115) in vitro and in vivo. In contrast to wild-type Bcl-x(L), a mutant Bcl-x(L) with the two threonines substituted by alanines (Ala-47, Ala-115) is a more potent inhibitor of ionizing radiation-induced apoptosis. These findings indicate that translocation of SAPK to mitochondria is functionally important for interactions with Bcl-x(L) in the apoptotic response to genotoxic stress.

Spread of beta-lactam-resistant Pseudomonas aeruginosa in a cystic fibrosis clinic

BACKGROUND

Pseudomonas aeruginosa colonisation of the airways of patients with cystic fibrosis (CF) is associated with considerable respiratory morbidity. Although segregation of colonised patients from non-colonised patients to prevent cross-infection has been recommended, there is little evidence that such cross-infection is widespread. We observed that a high proportion of children attending our CF clinic were colonised with P aeruginosa that was resistant to ceftazidime and other beta-lactam antibiotics. We used two genomic fingerprinting techniques to see whether this may have arisen from epidemic spread of a single strain.

METHODS

The prevalence of P aeruginosa colonisation and the antibiotic susceptibility of the organisms was determined from review of laboratory reports in the case-notes of 120 children with CF. Isolates were cultured from the sputum of 65 children colonised with ceftazidime-resistant P aeruginosa. Polymorphisms in total bacterial DNA from 92 isolates were analysed with two molecular fingerprinting techniques--pulsed-field gel electrophoresis after restriction enzyme digestion and assessment of flagellin gene polymorphisms by amplification of the whole gene and restriction enzyme digestion.

RESULTS

92 (76.7%) of 120 children were colonised with P aeruginosa, and 65 of the 92 harboured isolates that were resistant to ceftazidime. Only three of the 92 children had never been treated with ceftazidime. The results of the two molecular-fingerprinting techniques were concordant and showed that 55 of 65 children harboured the same epidemic strain. This strain was resistant to ceftazidime, azlocillin, and imipenem, and sensitive to tobramycin and ciprofloxacin.

INTERPRETATION

This study provides the first molecular evidence of a long-term outbreak of P aeruginosa in a CF centre. We suggest that careful surveillance of the prevalence of antibiotic resistance in CF centres should be instituted with measures to prevent cross-infection. We believe that antipseudomonal monotherapy should be considered with caution.

Human ocular dominance columns as revealed by high-field functional magnetic resonance imaging

We mapped ocular dominance columns (ODCs) in normal human subjects using high-field (4 T) functional magnetic resonance imaging (fMRI) with a segmented echo planar imaging technique and an in-plane resolution of 0.47 x 0.47 mm(2). The differential responses to left or right eye stimulation could be reliably resolved in anatomically well-defined sections of V1. The orientation and width ( approximately 1 mm) of mapped ODC stripes conformed to those previously revealed in postmortem brains stained with cytochrome oxidase. In addition, we showed that mapped ODC patterns could be largely reproduced in different experiments conducted within the same experimental session or over different sessions. Our results demonstrate that high-field fMRI can be used for studying the functions of human brains at columnar spatial resolution.

Generation by insulin of a chemical mediator that controls protein phosphorylation and dephosphorylation

Deproteinized skeletal muscle extracts free of major nucleotides from control and insulin-treated rats were fractionated and assayed for inhibition of protein phosphorylation by cyclic adenosine monophosphate (AMP)-dependent and -independent protein kinases. A differential effect of insulin on a particular fraction was observed on cyclic AMP-dependent protein kinase but not on cyclic AMP-independent protein kinases. This fraction that inhibited cyclic AMP-dependent protein kinase also stimulated glycogen synthase phosphoprotein phosphatase. It is proposed that this fraction may contain a mediator substance generateed in the presence of insulin.

Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue

A potent, orally active growth hormone (GH) secretagogue L-163,191 belonging to a recently synthesized structural class has been characterized. L-163,191 releases GH from rat pituitary cells in culture with EC50 = 1.3 +/- 0.09 nM and is mechanistically indistinguishable from the GH-releasing peptide GHRP-6 and the prototypical nonpeptide GH secretagogue L-692,429 but clearly distinguishable from the natural GH secretagogue, GH-releasing hormone. L-163,191 elevates GH in dogs after oral doses as low as 0.125 mg/kg and was shown to be specific in its release of GH without significant effect on plasma levels of aldosterone, luteinizing hormone, thyroxine, and prolactin after oral administration of 1 mg/kg. Only modest increases in cortisol were observed. Based on these properties, L-163,191 has been selected for clinical studies.

Mitochondrial translocation of protein kinase C delta in phorbol ester-induced cytochrome c release and apoptosis

Apoptosis is induced by the release of cytochrome c from mitochondria to the cytoplasm. The present studies demonstrate that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induces translocation of protein kinase C (PKC) delta from the cytoplasm to mitochondria. The results also show that translocation of PKCdelta results in release of cytochrome c. The functional significance of this event is further supported by the demonstration that PKCdelta translocation is required for TPA-induced apoptosis. These findings demonstrate that translocation of PKCdelta to mitochondria is responsible, at least in part, for inducing cytochrome c release and apoptosis.

A nonpeptidyl growth hormone secretagogue

A nonpeptidyl secretagogue for growth hormone of the structure 3-amino-3-methyl-N-(2,3,4,5-tetrahydro-2-oxo-1-([2'-(1H-tetrazol-5 -yl) (1,1'-biphenyl)-4-yl]methyl)-1H-1-benzazepin-3(R)-yl)-butanamid e (L-692,429) has been identified. L-692,429 synergizes with the natural growth hormone secretagogue growth hormone-releasing hormone and acts through an alternative signal transduction pathway. The mechanism of action of L-692,429 and studies with peptidyl and nonpeptidyl antagonists suggest that this molecule is a mimic of the growth hormone-releasing hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6). L-692,429 is an example of a nonpeptidyl specific secretagogue for growth hormone.

The synergistic effects of His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 on growth hormone (GH)-releasing factor-stimulated GH release and intracellular adenosine 3',5'-monophosphate accumulation in rat primary pituitary cell culture

His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6) stimulated GH release from rat primary pituitary cells in a time- and dose-dependent manner. Stimulation was observed after a 15-min, but not a 4-h, incubation. The concentrations of GHRP-6 required for half-maximal and maximal stimulation were 7 x 10(-9) and 10(-7) M, respectively. GH release induced by GHRP-6 was not affected by the addition of either naloxone or the GRF antagonist [N-Ac-Tyr1,D-Arg2]GRF-(1-29)-NH2. The latter inhibited GRF-stimulated GH release by shifting the dose-response curve to the right. His-D-Trp-D-Lys-Trp-D-Phe-Lys-NH2, an analog of GHRP-6, inhibited GH release stimulated by GHRP-6 without affecting that induced by GRF. When present together at maximal concentrations, GHRP-6 and GRF produced a synergistic effect on GH release. GHRP-6 had no effect on intracellular cAMP levels, whereas GRF increased intracellular cAMP concentrations by 3-fold. Combined treatment of pituitary cells with GRF and GHRP-6 resulted in a potentiation of the GRF-induced increase in cAMP levels. Basal GH release was reduced by 30% after pretreatment with GHRP-6 (10(-7) M) for 1 h. Pretreatment with GHRP-6 also decreased the subsequent response to GHRP-6, but not GRF. In contrast, pretreatment with GRF for 1 h had no effect on the subsequent action of GHRP-6 or GRF on GH release. The desensitization induced by GHRP-6 was completely reversed within 1 h after removal of the peptide. Results from this study indicate that GHRP-6 and GRF stimulated GH release from somatotrophs via different receptors and through discrete mechanisms.

TRPV4 mediates tumor-derived endothelial cell migration via arachidonic acid-activated actin remodeling

Changes in intracellular calcium [Ca(2+)](i) levels control critical cytosolic and nuclear events that are involved in the initiation and progression of tumor angiogenesis in endothelial cells (ECs). Therefore, the mechanism(s) involved in agonist-induced Ca(2+)(i) signaling is a potentially important molecular target for controlling angiogenesis and tumor growth. Several studies have shown that blood vessels in tumors differ from normal vessels in their morphology, blood flow and permeability. We had previously reported a key role for arachidonic acid (AA)-mediated Ca(2+) entry in the initial stages of tumor angiogenesis in vitro. In this study we assessed the mechanism involved in AA-induced EC migration. We report that TRPV4, an AA-activated channel, is differentially expressed in EC derived from human breast carcinomas (BTEC) as compared with 'normal' EC (HMVEC). BTEC display a significant increase in TRPV4 expression, which was correlated with greater Ca(2+) entry, induced by AA or 4αPDD (a selective TRPV4 agonist) in the tumor-derived ECs. Wound-healing assays revealed a key role of TRPV4 in regulating cell migration of BTEC but not HMVEC. Knockdown of TRPV4 expression completely abolished AA-induced BTEC migration, suggesting that TRPV4 mediates the pro-angiogenic effects promoted by AA. Furthermore, pre-incubation of BTEC with AA induced actin remodeling and a subsequent increase in the surface expression of TRPV4. This was consistent with the increased plasma membrane localization of TRPV4 and higher AA-stimulated Ca(2+) entry in the migrating cells. Together, the data presented herein demonstrate that: (1) TRPV4 is differentially expressed in tumor-derived versus 'normal' EC; (2) TRPV4 has a critical role in the migration of tumor-derived but not 'normal' EC migration; and (3) AA induces actin remodeling in BTEC, resulting in a corresponding increase of TRPV4 expression in the plasma membrane. We suggest that the latter is critical for migration of EC and thus in promoting angiogenesis and tumor growth.

Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

Biochemical characterization of the protein tyrosine kinase homology domain of the ErbB3 (HER3) receptor protein

The putative protein tyrosine kinase domain (TKD) of the ErbB3 (HER3) receptor protein was generated as a histidine-tagged recombinant protein (hisTKD-B3) and characterized enzymologically. CD spectroscopy indicated that the hisTKD-B3 protein assumed a native conformation with a secondary structure similar to that of the epidermal growth factor (EGF) receptor TKD. However, when compared with the EGF receptor-derived protein, hisTKD-B3 exhibited negligible intrinsic protein tyrosine kinase activity. Immune complex kinase assays of full-length ErbB3 proteins also yielded no evidence of catalytic activity. A fluorescence assay previously used to characterize the nucleotide-binding properties of the EGF receptor indicated that the ErbB3 protein was unable to bind nucleotide. The hisTKD-B3 protein was subsequently found to be an excellent substrate for the EGF receptor protein tyrosine kinase, which suggested that in vivo phosphorylation of ErbB3 in response to EGF could be attributed to a direct cross-phosphorylation by the EGF receptor protein tyrosine kinase.

Effects of dietary supplementation with enzymatically treated Artemisia annua on growth performance, intestinal morphology, digestive enzyme activities, immunity, and antioxidant capacity of heat-stressed broilers

The gastrointestinal tract is considered as one of the main target organs affected by heat stress. Phytogenic feed additives containing phenolics and flavonoids can improve the resistance of broilers to heat stress. This study was conducted to investigate the effects of dietary supplementation with enzymatically treated Artemisia annua (EA) on growth performance, intestinal morphology, digestive enzyme activities, immunity and antioxidant capacity of broilers challenged with heat stress. One hundred and forty-four 21-day-old male Arbor Acres broilers were randomly distributed into 3 treatments: 1) non-challenged control (CON); 2) heat-stress-challenged control (HS); and 3) heat-stress-challenged group + 1 g EA/kg diet (HS-EA). From 22 to 41 d, broilers in the CON group were housed at 22 ± 1°C, the HS and HS-EA groups, in which broilers were raised at 34 ± 1°C for 8 h (0900-1700 h) and the temperature for the rest time was the same as that of the CON group. The EA supplementation alleviated the compromised body weight gain and intestinal morphology impairment caused by heat stress challenge (P < 0.05). The EA attenuated heat-stress-induced decreased intestinal lipase, trypsin and total superoxide dismutase activities, and reduced intestinal secretory immunoglobulin A (SIgA) and IgG concentrations (P < 0.05). The EA inclusion prevented the elevation of intestinal malondialdehyde content and reduction of intestinal glutathione concentration induced by heat stress challenge (P < 0.05). The intestinal mRNA abundances of nuclear factor erythroid 2-related factor 2, heme oxygenase 1, glutathione peroxidase, gamma-glutamyl cysteine ligase larger catalytic subunit and gamma-glutamyl cysteine ligase smaller modulator subunit in heat-stressed broilers were increased in response to dietary EA treatment (P < 0.05). In conclusion, dietary supplementation of 1 g/kg EA could alleviate heat-stress-induced compromised growth performance and intestinal damage of broilers.

Human cortical regions activated by wide-field visual motion: an H2(15)O PET study

1. Several areas in the monkey dorsal visual pathway, including the dorsal part of the medial superior temporal area, have been found to contain cells responding to movements of a wide visual field and are suggested to be involved in analyzing self-induced motion information. In the present study, positron emission tomography was used to localize human cortical regions responding to wide-field visual motion. Changes in regional cerebral blood flow (rCBF) were measured when subjects maintained fixation and viewed low-contrast (0.15 log units brighter than the background) dots subtending 80 x 80 degrees and moving either coherently or incoherently. Brain foci were localized after activity in a fixation-only paradigm was subtracted from that in the two moving dot paradigms. 2. Both the coherent and incoherent movements significantly activated the primary/secondary visual cortex and surrounding visual areas in the cuneus and superior occipital gyrus. Subtraction of images between the coherent and incoherent movements showed that the activity caused by the two types of movement was comparable in these early visual cortical regions. 3. In the lateral occipitotemporoparietal cortex, the coherent movement specifically activated two separate areas; a posterior focus was located at the border of the right occipitotemporal gyri, and a dorsoanterior focus was located bilaterally in the temporoparietal cortex. The incoherent movement did not activate these regions. 4. A fine anatomic localization using individual magnetic resonance images was performed for the bilateral activation in the temporoparietal cortex, which was found to be located mainly in the depth of the inferior parietal lobule and a small portion of the superior and middle temporal gyri. 5. Both the coherent and incoherent movements activated a part of the superior parietal lobule located within the intraparietal sulcus (Brodmann area 7). The bilateral foci activated by the coherent movement were located more anteriorly than the focus activated by the incoherent movement. Subtraction images between the coherent and incoherent movements, however, did not reveal any significant rCBF increases in the superior parietal lobule. 6. Several other cortical regions known to be involved in visuospatial and visuomotor functions were also activated by the coherent movement, including the frontal eye field (Brodmann area 8) and premotor cortex (Brodmann area 6) in the frontal lobe. 7. The posteriorly located activation at the border of occipito-temporal gyri corresponds to the homologue of the middle temporal area reported in previous activation studies using small to medium-sized motion stimuli. The bilateral activation in the inferior parietal lobule appeared to rely on wide-field motion stimulation.

ErbB3 (HER3) interaction with the p85 regulatory subunit of phosphoinositide 3-kinase

ErbB3 (HER3), a unique member of the ErbB receptor family, lacks intrinsic protein tyrosine kinase activity and contains six Tyr-Xaa-Xaa-Met (YXXM) consensus binding sites for the SH2 domains of the p85 regulatory subunit of phosphoinositide 3-kinase. ErbB3 also has a proline-rich sequence that forms a consensus binding site for the SH3 domain of p85. Here we have investigated the interacting domains of ErbB3 and p85 by a unique application of the yeast two-hybrid system. A chimaeric ErbB3 molecule containing the epidermal growth factor receptor protein tyrosine kinase domain was developed so that the C-terminal domain of ErbB3 could become phosphorylated in the yeast system. We also generated several ErbB3 deletion and Tyr-->Phe site-specific mutants, and observed that a single ErbB3 YXXM motif was necessary and sufficient for the association of ErbB3 with p85. The incorporation of multiple YXXM motifs into the ErbB3 C-terminus enabled a stronger ErbB3/p85 interaction. The proline-rich region of ErbB3 was not necessary for interaction with p85. However, either deletion or mutation of the p85 SH3 domain decreased the observed ErbB3/p85 association. Additionally an ErbB3/p85 SH3 domain interaction was detected by an assay in vitro. These results were consistent with a model in which pairs of phosphorylated ErbB3 YXXM motifs co-operate in binding to the tandem SH2 domains of p85. Although a contributing role for the p85 SH3 domain was suggested, the N- and C-terminal SH2 domains seemed to be primarily responsible for the high-affinity association of p85 and ErbB3.

Relative contributions of bacteria, protozoa, and fungi to in vitro degradation of orchard grass cell walls and their interactions

To assess the relative contributions of microbial groups (bacteria, protozoa, and fungi) in rumen fluids to the overall process of plant cell wall digestion in the rumen, representatives of these groups were selected by physical and chemical treatments of whole rumen fluid and used to construct an artificial rumen ecosystem. Physical treatments involved homogenization, centrifugation, filtration, and heat sterilization. Chemical treatments involved the addition of antibiotics and various chemicals to rumen fluid. To evaluate the potential activity and relative contribution to degradation of cell walls by specific microbial groups, the following fractions were prepared: a positive system (whole ruminal fluid), a bacterial (B) system, a protozoal (P) system, a fungal (F) system, and a negative system (cell-free rumen fluid). To assess the interactions between specific microbial fractions, mixed cultures (B+P, B+F, and P+F systems) were also assigned. Patterns of degradation due to the various treatments resulted in three distinct groups of data based on the degradation rate of cell wall material and on cell wall-degrading enzyme activities. The order of degradation was as follows: positive and F systems > B system > negative and P systems. Therefore, fungal activity was responsible for most of the cell wall degradation. Cell wall degradation by the anaerobic bacterial fraction was significantly less than by the fungal fraction, and the protozoal fraction failed to grow under the conditions used. In general, in the mixed culture systems the coculture systems demonstrated a decrease in cellulolysis compared with that of the monoculture systems. When one microbial fraction was associated with another microbial fraction, two types of results were obtained. The protozoal fraction inhibited cellulolysis of cell wall material by both the bacterial and the fungal fractions, while in the coculture between the bacterial fraction and the fungal fraction a synergistic interaction was detected.

Heteromeric TRPV4-C1 channels contribute to store-operated Ca(2+) entry in vascular endothelial cells

There is controversy as to whether TRP channels participate in mediating store-operated current (I(SOC)) and store-operated Ca(2+) entry (SOCE). Our recent study has demonstrated that TRPC1 forms heteromeric channels with TRPV4 in vascular endothelial cells and that Ca(2+) store depletion enhances the vesicle trafficking of heteromeric TRPV4-C1 channels, causing insertion of more channels into the plasma membrane in vascular endothelial cells. In the present study, we determined whether the enhanced TRPV4-C1 insertion to the plasma membrane could contribute to SOCE and I(SOC). We found that thapsigargin-induced SOCE was much lower in aortic endothelial cells derived from trpv4(-/-) or trpc1(-/-) knockout mice when compared to that of wild-type mice. In human umbilical vein endothelial cells (HUVECs), thapsigargin-induced SOCE was markedly reduced by knocking down the expression of TRPC1 and/or TRPV4 with respective siRNAs. Brefeldin A, a blocker of vesicular translocation, inhibited the SOCE. These results suggest that an enhanced vesicular trafficking of heteromeric TRPV4-C1 channels contributes to SOCE in vascular endothelial cells. Vascular tension studies suggest that such an enhanced trafficking of TRPV4-C1 channels may play a role in thapsigargin-induced vascular relaxation in rat small mesenteric arteries.

Synthesis and biological activities of potent peptidomimetics selective for somatostatin receptor subtype 2

A series of nonpeptide somatostatin agonists which bind selectively and with high affinity to somatostatin receptor subtype 2 (sst2) have been synthesized. One of these compounds, L-054,522, binds to human sst2 with an apparent dissociation constant of 0.01 nM and at least 3,000-fold selectivity when evaluated against the other somatostatin receptors. L-054,522 is a full agonist based on its inhibition of forskolin-stimulated adenylate cyclase activity in Chinese hamster ovary-K1 cells stably expressing sst2. L-054,522 has a potent inhibitory effect on growth hormone release from rat primary pituitary cells and glucagon release from isolated mouse pancreatic islets. Intravenous infusion of L-054,522 to rats at 50 microgram/kg per hr causes a rapid and sustained reduction in growth hormone to basal levels. The high potency and selectivity of L-054, 522 for sst2 will make it a useful tool to further characterize the physiological functions of this receptor subtype.

Consistent and precise localization of brain activity in human primary visual cortex by MEG and fMRI

The tomographic localization of activity within human primary visual cortex (striate cortex or V1) was examined using whole-head magnetoencephalography (MEG) and 4-T functional magnetic resonance imaging (fMRI) in four subjects. Circular checkerboard pattern stimuli with radii from 1.8 to 5.2 degrees were presented at eccentricity of 8 degrees and angular position of 45 degrees in the lower quadrant of the visual field to excite the dorsal part of V1 which is distant from the V1/V2 border and from the fundus of the calcarine sulcus. Both fMRI and MEG identified spatially well-overlapped activity within the targeted area in each subject. For MEG, in three subjects a very precise activation in V1 was identified at 42 ms for at least one of the two larger stimulus sizes (radii 4.5 and 5.2 degrees ). When this V1 activity was present, it marked the beginning of a weak wave of excitations in striate and extrastriate areas which ended at 50 ms (M50). The beginning of the next wave of activations (M70) was also marked by a brief V1 activation, mainly between 50 and 60 ms. The mean separation between V1 activation centers identified by fMRI and the earliest MEG activation was 3-5 mm.

Comparison of neuronal selectivity for stimulus speed, length, and contrast in the prestriate visual cortical areas V4 and MT of the macaque monkey

1. Prestriate area V4 and the middle temporal area (MT) compose the first stage in which the ventral and dorsal visual cortical pathways are segregated. To better known the functional dichotomy between the two pathways at this level, we recorded cell responses from V4 and MT using anesthetized, immobilized macaque monkeys and compared the selectivity for speed of stimulus motion and stimulus length and the sensitivity to luminance contrast between the two areas. 2. V4 cells were as selective as MT cells for speed. The sharpness of tuning was not different between the two populations. The optimal speed varied widely in both areas, but both of the two distributions showed peaks at 32 degrees/s. 3. V4 and MT cells were similar in that about one-half of the cells (45% in V4 and 48% in MT) showed inhibition by long (16 degrees) bars. However, V4 cells preferred stimuli whose lengths were distributed around the lengths of the receptive field, whereas an overwhelming majority of MT cells preferred stimuli whose lengths were much shorter than the lengths of the receptive field. 4. The cutoff contrast at which one-half the maximum response was elicited was distributed widely in both areas, and the two distributions considerably overlapped. MT cells as a whole, however, were slightly more sensitive to the luminance contrast than V4 cells. 5. There was a tendency toward local clustering for cells with similar speed preferences in MT but not in V4. Pairs of MT cells recorded within 400 microns had smaller difference in the optimal speed than that of cell pairs taken randomly from the whole sample of MT cells.

A novel 3-substituted benzazepinone growth hormone secretagogue (L-692,429)

The 3-substituted benzazepinone, L-692,429 (compound 1), is the prototype compound of a novel class of compounds that stimulate release of growth hormone (GH). The molecule evolved from efforts to identify a non-peptide mimic of the growth hormone-releasing hexapeptide, GHRP-6. Compound 1 is prepared by sequential attachment of dimethyl-beta-alanine and 2'-biphenylyltetrazole side chains to a chiral 3-aminobenzolactam nucleus. Comparison of the biological activity of 1 with the corresponding six- and eight-membered lactam analogs shows the seven-membered benzazepinone skeleton to be preferred. Molecular modeling of the structurally diverse GH secretagogues, L-692,429 and GHRP-6, was performed.