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Biomedical subjects

J C Montgomery

Publications and source records attributed to J C Montgomery.

At least 37 records · Page 2Linked to original sources
PubMed1991

Identification of genes associated with tumor suppression in Syrian hamster embryo cells.

Loss of a tumor-suppressor gene function appears to play a critical role in the multistep process of neoplastic transformation of Syrian hamster embryo (SHE) cells in vitro. Clonal variants of two independent, preneoplastic cell lines have been isolated that have either retained (termed supB+) or lost (termed supB-) the ability to suppress the tumorigenicity of a highly malignant benzo[alpha]pyrene-transformed SHE cell line (BP6T) in cell hybrids. We have pursued several approaches in an attempt to identify genes that are responsible for tumor suppression in these cells. The only consistent differences detected in two-dimensional gel analyses of supB+ and supB- cellular proteins were decreases in the levels of two high molecular weight isoforms of tropomyosin in supB- cells. Differential screening of a supB+ cDNA library for genes that are preferentially expressed in supB+ cells yielded cDNA clones for four genes, i.e., collagen type II, collagen type IX, H19, and a previously unidentified gene (clone 5). Nuclear run-on assays suggested that higher transcription rates were responsible for the increased steady-state levels of some of these transcripts in supB+ cells. DNA sequence comparisons showed that two copies of a 9 bp element, previously identified in each of the mouse H19 enhancers, were also present in the 5' flanking region of the rat type II collagen gene. A transcription factor that controls expression of the collagen and H19 genes through binding to this conserved motif would be an attractive candidate for the supB+ gene or at least a mediator of the supB+ phenotype.

Animals↗
PubMed1991

Adaptation of sleep and circadian rhythms to the Antarctic summer: a question of zeitgeber strength.

Adaptation of sleep and circadian rhythms was examined in three temperate zone dwellers arriving in Antarctica during summer. Rectal temperature, wrist activity, and heart rate were monitored continuously, sleep timing and quality noted on awakening, and mood and fatigue rated every 2 h while awake. Sleep was poorer in 2/3 subjects in Antarctica, where all subjects reported more difficulty rising. Sleep occurred at the same clock times in New Zealand and Antarctica, however, the rhythms of temperature, activity, and heart rate underwent a delay of about 2 h. The subject with the most Antarctic experience had the least difficulty adapting to sleeping during constant daylight. The subject with the most delayed circadian rhythms had the most difficulty. The delay in the circadian system with respect to sleep and clock time is hypothesized to be due to differences in zeitgeber strength and/or zeitgeber exposure between Antarctica and New Zealand.

Activities of Daily Living↗
PubMed1991

Psychological and sexual aspects of the menopause.

Female psychiatric morbidity appears to be highest during the middle years, with an apparent increase around the time of the menopause. Oestrogen replacement therapy may improve psychological symptoms, but the effects of testosterone and progestogens are less clear. There appears to be an adverse effect of both increasing age and the menopause on sexuality, with no clear benefit of oestrogen therapy. Exogenous testosterone may have a role in the treatment of sexual dysfunction.

Depressive Disorder↗
PubMed1990

Effects of temperature on nervous system: implications for behavioral performance.

Temperature change has a major impact on the function of the nervous system and its components, including altering synaptic gain and changing synaptic and conduction delays. Although many animals are subject to changes in body temperature, the degree of temperature change actually experienced by many poikilotherms is not well documented. The fact that many animals continue to exhibit coordinated sensorimotor function during changes in body temperature indicates that some form of temperature compensation has occurred within the nervous system. Compensations may occur automatically (opposing effects of temperature offsetting each other), they may be an inherent property of closed-loop systems, or they may be effected by more sophisticated control mechanisms such as those of the vertebrate cerebellum.

Action Potentials↗
PubMed1989

The volunteer spirit is alive and well at Scottish Rite Hospital. Interview by Melissa Gaskill.

Today, Scottish Rite Hospital for Crippled Children in Dallas serves 10,000 Texas children with the help of 600 or so volunteers who log about 82,000 hours a year. This astonishing volunteer program has earned the hospital awards and recognition--including this year's AHA award for the outstanding volunteer program in Region 7--and has helped create the warm, team atmosphere that sets this hospital apart. President J.C. Montgomery takes pride in his volunteers and in the other part of that team, the paid staff. A member of the Texas Hospital Association board of trustees, he is also on the board of the Texas Hospital Education and Research Foundation and chair of that group's Investment Committee. Health Texas recently visited with Montgomery about the hospital and the volunteer program.

Hospital Bed Capacity, under 100↗
PubMed1988

Temperature compensation in the vestibulo-ocular reflex: a novel hypothesis of cerebellar function.

Some ectothermic animals are subject to changes of body temperature during routine activity. How are they able to maintain co-ordinated behaviour? Analysis of the available evidence on the effects of temperature on the vestibulo-ocular reflex suggests that there will be a degree of automatic temperature compensation. Temperature will increase the gain of some components of the reflex, and decrease the gain of others resulting in a reduced temperature sensitivity of the overall reflex. It is suggested that the cerebellum may provide the balance of temperature compensation required to maintain adequate reflex function. The hypothesis is that type III (bidirectionally sensitive) Purkinje cells receive temperature information as a common-mode signal from the opposing labyrinths, and use this information to regulate the gain of the vestibulo-ocular reflex pathway.

Animals↗
PubMed1987

Effect of oestrogen and testosterone implants on psychological disorders in the climacteric.

In a double-blind trial oestradiol, oestradiol/testosterone, or placebo implants were assessed for their effects on psychological symptoms in women attending a menopause clinic. After two months, women receiving active treatment scored better than the placebo group on a self-rating scale of distress, on anxiety, and on depression (p less than 0.05). Postmenopausal but not perimenopausal women improved after placebo, and at 4 months the scores in the three groups no longer differed significantly.

Adult↗
PubMed1986

A vestibulo-ocular reflex with no head movement.

Eye movements were produced in an elasmobranch preparation by electrical stimulation of the horizontal canal ampullary nerves. A pseudorandom binary sequence of stimulus pulse trains was delivered bilaterally. Eye position during this stimulus was cross-correlated with the stimulus pattern to obtain a linear model of the response. Sums of exponential functions were fitted to the crosscorrelogram data to estimate time-constants and transfer functions. The data was examined in the frequency domain by using Fourier transformation. The response is accurately described by a second order linear filter, which is essentially a low pass filter with a cutoff at 0.22 Hz. This nearly two octaves below the cutoff frequency of the eye motor plant, which has been estimated by the same method. Our data shows that there is no central phase compensation or prediction which might offset the substantial delay in eye motor plant response. We hypothesise that the necessary phase compensation may be achieved by driving the vestibulo-ocular reflex with sensory neurons having a phase advance at high frequency.

Animals↗
PubMed1986

Elasmobranch eye motor dynamics characterised using pseudorandom stimulus.

A pseudorandom binary sequence electrical pulse rate stimulus was delivered to the abducens nerve of an elasmobranch preparation. Ipsilateral eye movements were recorded using a position-sensitive photodiode to measure the position of a reflective patch attached to the fish's eye. Eye position data was cross-correlated with the stimulus pattern, and exponential decay curves were fitted to the cross-correlograms to estimate the time constant of a linear first order low-pass filter model. The cross-correlograms were transformed into the frequency domain using a Digital Fourier Transform, and Bode plots of eye dynamics were plotted. Eye motor plant dynamics in the elasmobranch Cephaloscyllium isabella can be accurately characterised by a linear first order low-pass filter model with a corner frequency of 0.73 +/- 0.10 Hz. Non-minimum phase lag reaches 90 degrees at about 4 Hz, indicating a time delay of some 50-60 ms. Integration of the canal signal is not required for producing compensatory eye movements above the characteristic frequency of the eye motor plant. However, the canal signal may be integrated to ensure that the vestibulo-ocular reflex is compensatory at lower frequencies. Substantial phase compensation or prediction is required for effective control of the vestibulo-ocular reflex.

Abducens Nerve↗
PubMed1985

Comparison of the 5' regions of human and mouse carbonic anhydrase II genes and identification of possible regulatory elements.

The nucleotide sequence of the 5' region of the human carbonic anhydrase II gene has been determined. This sequence begins 643 base pairs upstream from the ATG start site and continues through exon 1, intron 1, exon 2 and the adjoining 125 nucleotides of intron 2. The human sequence is compared with homologous regions of the mouse (YBR strain) carbonic anhydrase II gene by aligning the two sequences for optimal homology. In addition to a TATA box and a putative CCAAT box (CCACC in human and CCACT in mouse), three conserved tandem-repeat elements in mouse and two in human (consensus: cCNGTCACCTCCgC) are located 15 and 22 base pairs upstream, respectively, from the CCAAT boxes in the human and mouse sequences. This repeat element is similar to a tandem repeat sequence located at about the same position in mammalian beta-globin genes, and may represent regulatory elements common to both the carbonic anhydrase and beta-globin genes. The regions surrounding exon 1 are extremely G + C-rich in both human and mouse genes. In addition, several CCGCCC or GGGCGG sequences which may be important for transcriptional efficiency are found in the 5' flanking regions of the human and mouse genes.

Amino Acid Sequence↗
PubMed1985

Structure and exon to protein domain relationships of the mouse carbonic anhydrase II gene.

We have isolated a cosmid clone containing the entire mouse (YBR strain) carbonic anhydrase (CA) II gene in 38 kilobase pairs of genomic DNA. The gene was found to be composed of seven exons and six introns. A TATA box (TATAAAA) and a possible CCAAT box (CCACT) have been located beginning 92 and 142 base pairs, respectively, upstream from the initiation codon ATG. When the regions encoded by exons and protein domains are examined, all but 1 of the 30 putative active site residues are encoded by four exons: exons 2 and 3 mainly code for hydrophilic residues and exons 4 and 6 mostly hydrophobic residues. Two intron splice positions, one between the codons for Glu-116 and Leu-117 and the other interrupting the codon for Gly-143, are located at the bottom of the active site cavity, and the former separates two of the three histidine residues forming ligands to the active site zinc ion. The other four splice sites map to the exterior of the molecule. Thus, except for the possible association of the 29 active site residues encoded by four exons, no obvious correspondence is seen between the regions coded by exons and the functional or secondary structural domains of the mouse CA II molecule. During this study, the possible basis for the two electrophoretic types, CA IIa and CA IIb, of inbred mouse strains was detected as a Gln/His interchange at position 38.

Amino Acid Sequence↗
PubMed1985

Functional morphology of the piper Hyporhamphus ihi with reference to the role of the lateral line in feeding.

As a basis for understanding the function of the halfbeak of the piper Hyporhamphus ihi (Phillips), details of the structure and dimensions of the anterior lateral line on the head and lower jaw of the piper are described. The anterior lateral line is composed of a series of cranial canals; the supraorbital-postorbital canal; the suborbital canal; and the preopercular-mandibular canal which extends along the lower jaw. Each canal opens to the surface by a series of pores, and individual neuromasts exist in specialized regions of the canals between each of the pores. Piper are nocturnal plankivores and they possess the feeding structures and digestive tract suited to this diet. The hypothesis is proposed that they use the anterior lateral line system in prey detection, and this paper shows that the piper's elongate body form, swimming behaviour, and lack of a specialized visual system are all consistent with this hypothesis.

Animals↗
PubMed1985

Field and laboratory studies of the feeding behaviour of the piper Hyporhamphus ihi with reference to the role of the lateral line in feeding.

Piper school in large groups close to the water surface during daylight hours, whereas at night the schools break up and individual fish can be observed swimming slowly through the water. Analysis of gut contents indicates that during the day piper feed primarily on copepods, and terrestrial insects trapped on the water surface; after dark the demersal zooplankton which enter the water column form the major dietary component. Prey selectivity is evident in that certain groups present in the plankton are not found in the stomach contents of piper, and that the size of prey taken is biased towards the larger size classes of plankton. Laboratory experiments establish that piper are capable of locating prey in total darkness, and that under these conditions live prey are consumed in a higher proportion, and much more quickly than dead prey. These results strengthen the hypothesis that piper use their anterior lateral line to feed on zooplankton at night.

Animals↗