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Biomedical subjects

G Holt

Publications and source records attributed to G Holt.

At least 55 records · Page 3Linked to original sources
PubMed1992

Necrotizing lesions in the intestine, gizzard, and liver in captive capercaillies (Tetrao urogallus) associated with Clostridium perfringens.

During the period from 1982 to 1991, 863 captive and 32 wild capercaillies (Tetrao urogallus) were necropsied. The most common cause of death in captive capercaillies was necrotizing enteritis, diagnosed in 110 (13%) birds. Of these, 31 (28%) birds also had necrotizing lesions in the liver. Necrotizing gastritis occurred in 29 birds, two of which had concurrent necrotizing enteritis. In the capercaillies with necrotizing enteritis, Clostridium perfringens type A was isolated more frequently and in larger numbers than in birds which died from other causes. Thus, Clostridium perfringens type A may be of etiological importance in necrotizing enteritis. Necrotizing enteritis was not diagnosed in wild capercaillies.

Animals↗
PubMed1991

Cloning and selective overexpression of an alkaline protease-encoding gene from Aspergillus oryzae.

The gene alpA encoding Aspergillus oryzae alkaline protease (ALP) was isolated from a genomic library of an industrial strain used in Thailand by using oligodeoxyribonucleotide probes based on the published cDNA sequence [Tatsumi et al., Agric. Biol. Chem. 52 (1988) 1887-1888]. The entire nucleotide sequence of the genomic clone obtained was determined. By comparison with the published cDNA sequence, it was found that ALP is encoded by four exons of 314, 445, 89 and 351 bp. Three introns, which interrupt the coding sequence, are 50, 59 and 56 bp in length. The gene contains a typical TATA box 103 bp upstream from the start codon, and a consensus polyadenylation signal, AATAAA, 189 bp from the stop codon. The alpA gene, introduced into a protease deficient strain (A. oryzae U1638) by cotransformation, directed the secretion of enzymatically active ALP into the culture medium. Cotransformants of the high-level ALP-producing strain U212 containing multiple copies of the alpA gene were able to secrete up to five times more ALP than the parental strain.

Amino Acid Sequence↗
PubMed1991

Acrosome reaction induced by immunoaggregation of a proteinase inhibitor bound to the murine sperm head.

ZP3, a glycoprotein of the murine zona pellucida, functions both to bind acrosome intact sperm and to induce the acrosome reaction. Solubilized whole zonae as well as purified ZP3 are able to induce acrosome reactions in capacitated sperm. Pronase digests of whole zonae yield glycopeptides that bind to sperm but are unable to induce acrosome reactions. However, immunoaggregation of these glycopeptides results in the exocytosis of the acrosome in the majority of treated sperm. The data suggest that ZP3 triggers the acrosome reaction by the aggregation of ZP3 binding sites on the sperm head. If aggregation of ZP3 binding sites is important in the induction of the acrosome reaction, then it may be possible to induce the acrosome reaction in the absence of zona by immunoaggregation of the sites. This presentation deals with the immunoaggregation of a proteinase inhibitor of seminal vesicle origin (SVI) that binds to a site on the sperm head known to participate in zona binding. We show that capacitated murine sperm, pretreated with the SVI, will acrosome react, as determined by Coomassie brilliant blue staining, when incubated with rabbit antiinhibitor antiserum (anti-SVI). The percentage of SVI-treated sperm displaying an acrosome reaction is dependent on the concentration of the immune serum. Sperm stain positive for intact acrosomes when anti-SVI Fab fragments or normal rabbit serum is substituted for the immune serum. However, when capacitated sperm, treated with both SVI and anti-SVI Fab fragments, are incubated with goat antirabbit IgG, the majority of sperm acrosome react. The data suggest that the aggregation of SVI bound to the sperm surface, in the absence of zona glycoproteins, is sufficient to induce the acrosome reaction.

Acrosome↗
PubMed1991

Spatiotemporal mechanisms in receptive fields of visual cortical simple cells: a model.

1. Simple cells in the visual cortex have been subdivided into nondirection-selective (NDS), direction asymmetric (DA), and direction-selective (DS) cells. DA cells reverse their preferred direction with reversal of the stimulus contrast; DS2 cells respond with the same preferred direction for light and dark stimuli, whereas DS1 cells respond only to one (light or dark) contrast. Also, four velocity response groups have been distinguished: velocity broadband, low-pass, high-pass, and -tuned cells. This study describes an analytic model of feed-forward spatiotemporal interactions within a receptive field that reproduces these basic features of cortical simple cell behavior in the cat. 2. The spatial structure of the receptive fields is simulated with Gabor functions. Two neurobiologically plausible mechanisms, temporal low-pass filtering and intracortical spatial distribution of activity, are modeled. The central feature of the study is the implementation of both mechanisms in a spatially continuous way. The model is analytic, but an equivalent neural network diagram was drawn and is used to explain the features of the model. 3. First-order temporal low-pass filtering is performed both after convolving the stimulus light-intensity function with the Gabor type receptive field and also at the final output step of the model. In the circuit diagram this would correspond to low-pass filtering in lateral geniculate nucleus (LGN) and cortical cells. Filtering was adjusted to have a -3-dB drop-off frequency of 2-3 Hz, corresponding to the drop-off frequencies observed in response to temporal modulation of sine-wave gratings. 4. The mechanism that we call intracortical distribution of activity is implemented along the axis of stimulus motion. A response elicited from the part of the receptive field that is stimulated at a given time will spread out in the receptive field, influencing regions that have not been stimulated. It is equivalent to spreading of activity on the cortical surface. This mechanism extends the existing ideas of discrete interactions between subfields to a continuous scheme throughout the whole receptive field. It is based on findings that intracortical interactions exist even within single subfields. The impact of distributing the activity is assumed to decrease exponentially with the Euclidian distance between the stimulated region and the region under consideration. 5. Thresholds are implemented only at the level of the cortex. Both the activity distributing mechanism and the output of the cell being studied are thresholded.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Predicted structure of the bovine calcitonin gene-related peptide and the carboxy-terminal flanking peptide of bovine calcitonin precursor.

We have isolated from a bovine genomic library a clone which contains the calcitonin (CT) and CT gene-related peptide (CGRP) sequences, using probes representing the human CT and CGRP sequences. Sequence analysis has identified the nucleotide sequence coding for bovine CT, its C-terminal flanking peptide and bovine CGRP. The deduced amino acid sequence of bovine CGRP revealed a significant homology with other CGRPs so far reported. It differs by only one amino acid from rat CGRP alpha and porcine CGRP, and by three and four amino acids from human CGRP beta and alpha respectively. Bovine CT has, however, only 14 out of 32 residues in common with human CT. As in the human CT precursor, the C-terminal flanking peptide of bovine CT precursor is a 21 amino acid peptide. It shares only 11 residues in common with its human counterpart. This study thus provides further evidence that CGRP, in contrast to CT and its C-terminal flanking peptide, is a highly conserved molecule.

Amino Acid Sequence↗
PubMed1990

The genetic stability of Penicillium chrysogenum transformants in a fermentor.

A number of transformants of Penicillium chrysogenum have been obtained with the plasmid vector p3SR2. Southern analysis showed that transformation had occurred by integration of vector sequences into the nuclear DNA of the fungus. A number of transformants were tested for stability of the transformed phenotype in agar medium and some were found to be unstable. Two transformants, shown to be stable in agar culture, were grown in 5-1 batch fermentors for further stability tests. Over periods of up to 312 h in the fermentor both transformants were 100% stable with respect to the transformed phenotype. In addition Southern analysis of DNA extracted from the spent mycelium showed that no change had occurred in the position of the integrated vector sequences within the transformant nuclear DNA.

Blotting, Southern↗
PubMed1990

Levels of polychlorinated biphenyls, organochlorine pesticides, mercury, cadmium, copper, selenium, arsenic, and zinc in the harbour seal, Phoca vitulina, in Norwegian waters.

Residue levels of the chlorinated hydrocarbons polychlorinated biphenyls (PCBs), total DDT, alpha-, beta- and gamma-hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), and oxychlordane in blubber, and the elements mercury, cadmium, copper, selenium, arsenic, and zinc in liver, of 82 harbour seals, Phoca vitulina, were determined. The seals were found dead or dying in Norwegian waters during the disease outbreak caused by a morbilli virus in 1988. Of the chlorinated hydrocarbons, the highest concentrations were found of PCBs, which were 2-4 times higher than the total DDT concentrations. P,p'-DDE was the main contributor to the total DDT, and constituted about 80%. The PCB and total DDT concentrations ranged from 0.4-38 and 0.1-8.8 mg kg(-1), respectively. The mercury concentrations ranged from 0.1-89 mg kg(-1). Significantly higher mean levels of PCBs (13 mg kg(-1) and mercury (16 mg kg(-1)) were found in blubber and liver, respectively, of seals from the Southern coast of Norway, as compared to the corresponding mean levels in seals from the Oslofjord (8.8 and 4.1 mg kg(-1)), and at the Northwestern coast (5.8 and 7.9 mg kg(-1)), respectively. A significant positive correlation was found between the concentrations of selenium and mercury. When the seals were grouped according to sex and age, females of ageclass > 1 and pups of both sexes had significantly lower PCB and total DDT levels than males ageclass > 1. Significantly higher hepatic mercury levels were found in seals ageclass > 1 as compared to pups. Only low levels of the other organochlorines, cadmium and arsenic, were found. Copper and zinc were considered to be present at normal physiological levels. The present organochlorine and heavy metal concentrations gave no support to suggestions that organochlorines and heavy metal pollution may be directly involved in the observed seal deaths.

Journal Article↗
PubMed1990

Nematode related spinal myelomeningitis and posterior ataxia in muskoxen (Ovibos moschatus).

In the fall of 1988 all five animals in a herd of muskoxen (Ovibos moschatus) developed clinical signs of posterior ataxia. Postmortem investigation revealed inflammatory lesions of the caudal part of the spinal cord, mainly as leptomeningitis. Nematodes were seen in close association with the lesions. Although not identified, the parasites were probably an Elaphostrongylus sp.

Animals↗
PubMed1989

A high-performance liquid chromatography method for the simultaneous assay of diaminopimelate epimerase and decarboxylase.

A sensitive and comparatively simple method for the assay of diaminopimelate (DAP) decarboxylase, which simultaneously monitors DAP epimerase activity, in the reverse of the biosynthetic direction, is described. The substrate, meso-DAP and products LL-DAP and L-lysine are derivatized with o-phthaldialdehyde and resolved by reversed-phase high-performance liquid chromatography. Separation is achieved on a Spherisorb C18 column using a gradient elution system. This technique offers a high degree of sensitivity as the detection method described can measure picomole quantities of substrate and products.

Amino Acid Isomerases↗
PubMed1989

Bedside blood gas and electrolyte monitoring in critically ill patients.

A major advantage of near-patient testing is time savings that facilitate important diagnostic and therapeutic decisions. Recent technologic advances have made available a number of systems that allow for near-patient testing. The reliability of these instruments must be validated in the clinical setting in the hands of their intended users. We evaluated the Gemstat blood gas, electrolyte, and Hct portable analyzer in the critical care setting when used by numerous individuals with no previous laboratory training. Blood gas, Na, K, and Hct results were highly correlated with those from the clinical laboratories (PaO2, r = .96; PaCO2, r = .92, pH, r = .96; Na, r = .93; K, r = .95; Hct, r = .91). The Gemstat represents a new generation of portable, rapid, safe, and accurate instruments that are well suited for ICU settings. The instrument can facilitate clinical management of patients, and may improve patient care.

Blood Gas Analysis↗
PubMed1989

Chronic whole body sympathectomy fails to protect ischemic rabbit hearts.

We determined whether chronic chemical sympathetic denervation could protect the rabbit heart against ischemia. Rabbits received 10 mg/kg 6-hydroxydopamine (6-HD) twice during the first week, then 100 mg.kg-1.wk-1 for the following 7 wk. After this interval the rabbits were anesthetized, the chests were opened, and in each a coronary branch was occluded for 45 min followed by reperfusion for 3 h. Collateral flow was determined with radioactive microspheres during coronary occlusion. Flow to the ischemic myocardium of the 6-HD group (0.06 +/- 0.03 ml.min-1.g-1) was not significantly different from that in the control group (0.04 +/- 0.02 ml.min-1.g-1). Infarct size was determined with triphenyltetrazolium chloride staining. Average infarct size calculated as a percentage of risk zone was similar in the 6-HD and control groups (59 +/- 15 and 60 +/- 12%, respectively). We conclude that chronic chemical sympathectomy does not induce collateral growth in the rabbit heart. Furthermore, endogenous catecholamines do not contribute to injury in the ischemic rabbit heart.

Animals↗
PubMed1989

Expression of the trpC gene from Penicillium chrysogenum in Aspergillus nidulans.

The heterologous expression in Aspergillus nidulans of a gene involved in tryptophan biosynthesis from Penicillium chrysogenum is described. With the chimeric plasmid pPC-31, which carries the cloned trpC gene, approximately 10-40 "stable" transformants per microgram of DNA were obtained, with selection for complementation of the mutant allele. This frequency was increased 10-fold by the insertion of the ans1 fragment into the transformation vector. Southern hybridization analysis revealed that transformation occurred as a consequence of the integration of vector sequences into the host chromosome at a variety of sites within the genome.

Aspergillus nidulans↗
PubMed1988

A differential nuclear uptake and retention of 3H-androgens in the thyroids of baboons.

Women have a greater incidence of autoimmune thyroiditis, thyroid cancer and radiation-induced carcinogenesis than men. Over the past several years we have examined for the presence of steroid receptors in both humans and non-human primates. In this study we examined the nuclear uptake and retention of 3H-testosterone, the main circulating androgen in mammals, in different cells of the thyroid gland of baboons, our non-human primate model. Castrated-adrenalectomized male baboons were injected with 3H-testosterone (1 microgram/kg bw) and killed 1 1/2 h later. The thyroid glands and other tissues were removed and processed for autoradiography. Nuclear localization of 3H-testosterone or one of its metabolites was found in a small fraction of the follicular cells (approximately 10-20%). The discrepancy between these findings and those previously obtained with 3H-dihydrotestosterone (virtually 100% of the follicular cells concentrated the 3H-steroid) are discussed. The results from this study and those of the past strongly support a direct action of androgen on the thyroid. Whether a direct action of androgen on the thyroid is related to smaller incidence in autoimmune thyroiditis, thyroid cancer and radiation-induced carcinogenesis in men than women remains an unanswered question at the present time.

Androgens↗