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Biomedical subjects

L Kerr

Publications and source records attributed to L Kerr.

35 records · Page 2Linked to original sources
PubMed1990

Analysis of sperm function in globozoospermia: implications for the mechanism of sperm-zona interaction.

The globozoospermic condition has provided a unique opportunity to determine how the abnormal mitochondrial organization and acrosomal loss associated with this syndrome, influence sperm function. Despite the abnormal midpiece architecture, the movement characteristics of the spermatozoa, in terms of the curvilinear, path, and progressive velocities, amplitude of head displacement, and hyperactivation were all within the normal range. Similarly, the behavior of the spermatozoa on Percoll gradients was normal, although the capacity of the isolated fractions to generate reactive oxygen species was negligible. Of particular significance was the fact that the globozoospermic spermatozoa were incapable of sperm-oocyte fusion or binding the human zona pellucida, even after an intracellular calcium signal had been generated with the ionophore A23187. The sudden induction of sperm-zona interaction could, however, be achieved by the use of a ferrous ion promoter system to induce limited lipoperoxidation. This result demonstrates that the enhancing effect of peroxidation on sperm-zona adhesion involves a direct action on the properties of the sperm-plasma membrane, rather than an indirect consequence of acrosomal damage and acrosin leakage. Such findings emphasize the value of specific teratozoospermic conditions, such as globozoospermia, in dissecting the mechanisms that regulate human sperm function.

Adult↗
PubMed1987

Function of the Y optic nerve fibres in the cat: do they contribute to acuity and ability to discriminate fast motion?

1. A controlled pressure block has been applied to the optic nerve of the cat, sufficient to bring about degeneration of the axons of the large (Y) nerve fibres caudal to the block site. This degeneration has been monitored by means of implanted electrodes in optic nerve and tract which have shown a loss of the short-latency (t1) response 4-6 days after the block, and also by histological examination of the optic nerve. 2. Cats with one optic nerve blocked in this way have been used in behavioural experiments, one or other eye being covered during the tests. Tested via the blocked nerve, all cats with loss of only Y fibres could perform certain tests: the visual placing reaction, the blink reflex, the pupillary (light) reflex and simple manoeuvres such as walking a plank and jumping from table to floor. 3. When acuity was tested by means of the Mitchell jumping apparatus, cats with loss of only Y fibres showed the same acuity using either eye. This was true also of one cat in which many X fibres had also degenerated, as evidenced by a 55% loss of the medium-latency (t2) response, but in another cat with 90% loss of the t2 response acuity was reduced to about half-normal. 4. Ability to discriminate fast motion was tested by a modification of the Mitchell apparatus. All cats were able to discriminate the motion of an 11.5 deg spot up to a velocity of 6260 deg/s, whether using their normal eye or their affected eye. However, the loss of the Y fibres reduced the ability to discriminate fast motion, so that for any given level of contrast the velocity which could be discriminated was about two-thirds of the velocity discriminated using the normal eye. The ability of the cat to discriminate fast motion seems to be similar to that of the human. 5. These results suggest that there is no sharp restriction of function between the Y and X systems but instead considerable overlap. However, each system possesses specialized features giving it superiority in certain conditions.

Animals↗
PubMed1985

Conus geographus toxins that discriminate between neuronal and muscle sodium channels.

We describe the properties of a family of 22-amino acid peptides, the mu-conotoxins, which are useful probes for investigating voltage-dependent sodium channels of excitable tissues. The mu-conotoxins are present in the venom of the piscivorous marine snail, Conus geographus L. We have purified seven homologs of the mu-conotoxin set and determined their amino acid sequences, as follows, where Hyp = trans-4-hydroxyproline. GIIIA R.D.C.C.T.Hyp.Hyp.K.K.C.K.D.R.Q.C.K.Hyp.Q.R.C.C.A-NH2 [Pro6]GIIIA R.D.C.C. T.P.Hyp.K.K.C.K.D.R.Q.C.K.Hyp.Q.R.C.C.A-NH2 [Pro7]GIIIA R.D.C.C.T.Hyp.P.K.K.C.K.D.R.Q.C.R.Hyp.Q.R.C.C.A-NH2 GIIIB R.D.C.C.T.Hyp.Hyp.R.K.C.K.D.R.R.C.K.Hyp.M.K.C.C.A-NH2 [Pro6]GIIIB R.D.C.C.T.P.Hyp.R.K.C.K.D.R.R. C.K.Hyp.M.K.C.C.A-NH2 [Pro7]GIIIB R.D.C.C.T.Hyp.P.R.K.C.K.D.R.R.C.K.Hyp.M.K.C.C.A-NH2 GIIIC R.D.C.C.T.Hyp.Hyp.K.K.C.K.D.R.R.C.K.Hyp.L.K.C.C.A-NH2. Using the major peptide (GIIIA) in electrophysiological studies on nerve-muscle preparations and in single channel studies using planar lipid bilayers, we have established that the toxin blocks muscle sodium channels, while having no discernible effect on nerve or brain sodium channels. In bilayers the blocking kinetics of GIIIA were derived by statistical analysis of discrete transitions between blocked and unblocked states of batrachotoxin-activated sodium channels from rat muscle. The kinetics conform to a single-site, reversible binding equilibrium with a voltage-dependent binding constant. The measured value of the equilibrium KD for GIIIA is 100 nM at OmV, decreasing e-fold/34 mV of hyperpolarization. This voltage dependence of blocking is similar to that of tetrodotoxin and saxitoxin as measured by the same technique. The tissue specificity and kinetic characteristics suggest that the mu-conotoxins may serve as useful ligands to distinguish sodium channel subtypes in different tissues.

Amino Acid Sequence↗
PubMed1983

Uptake of horseradish peroxidase by axons of passage and its modification by poly-L-ornithine and dimethylsulphoxide.

It has been shown that transected axons of passage in the optic tract can take up horseradish peroxidase (HRP) and transport it back to the cell bodies. This effect is considerably reduced if the HRP is injected from a small-tipped micropipette 6-12 h after insertion into the injection site. HRP is not taken up by uninjured axons of passage. The use of poly-L-ornithine and dimethylsulphoxide dramatically increases the numbers of labeled cells. These numbers are undiminished after 6-12 h waiting periods. From this and from calculation it is clear that much of this effect must occur via uninjured axons. These substances should not be used in any situation where it is important not to label axons of passage. If other HRP conjugates and additives have the same effect as those described here, the results of experiments with these substances should be interpreted with caution.

Animals↗
PubMed1983

Dental problems in athletes.

The high performance standards required of an Olympic athlete can only be attained by a totally healthy individual. Optimal dental health is a necessary element. The universality of dental disease can be altered by modern prevention modalities and self-administered hygiene. Nonetheless, any dental or medical program of care should be prepared for the treatment of dental disease and trauma. Suggested is a program of prevention and treatment grounded in modern basic science and dealing with the overlay of the sociopsychological phenomena, which is an essential part of effective health care.

Adolescent↗
PubMed1981

An accurate method for the continuous measurement of oxygen consumption in infants during cardiac catheterization.

This paper describes the assessment of a method for measuring the oxygen consumption of infants and young children that is suitable for use in the cardiac catheterization laboratory. It is based upon the open-circuit technique and permits the continuous display of the oxygen consumption during the investigative procedures. The accuracy of the apparatus was assessed over the range 40-200 ml/min, both in vitro and in vivo. It was found that the apparatus was free from systematic error and that it had a random error of approximately 2% of the measured value.

Cardiac Catheterization↗
PubMedDate not supplied

Special needs children in the public schools: perceptions of school nurses and school teachers.

Schools are faced with the challenges presented by special needs children (SNC) because the law requires that they must provide educational opportunities to all children--those who have no handicapping conditions as well as those who do, no matter how severe those conditions. The need exists for adequately prepared health care professionals in the school setting. Using a convenience sample of school teachers and school nurses, this investigation focused on the perceptions of school teachers and nurses regarding the challenges and demands of having these children in the public school. Two surveys were conducted to study those perceptions. Quantitative and qualitative data analyses showed that the needs of both groups of providers--school nurses and school teachers--can be summed up in three categories: information dissemination, communication, and resource integration. Infrastructure development involves the establishment of an effective information management system, effective use of such a system in establishing communications between all participants, and adequate administrative support to facilitate the development of the school providers' sense of competence in the care of SNC. A well-planned and adequately supported program goes a long way toward changing people's attitudes toward the inclusion of SNC in the classroom.

Adolescent↗
PubMedDate not supplied

Congenital esophageal hiatal hernia in the Chinese shar-pei dog.

Esophageal hiatal hernia was diagnosed in 11 young Chinese Shar-Pei dogs between October 1985 and July 1991. The dogs ranged in age from 2 to 11 months and included 3 females and 8 males. The most common clinical signs were regurgitation, vomiting, and hypersalivation. Physical examination was normal in 6 dogs; abnormal physical examination findings in the other 5 dogs included fever, dehydration, hypersalivation, and pulmonary wheezes and crackles. Laboratory evaluation was significant only for neutrophilia in 5 dogs. A diagnosis of hiatal hernia was made on the basis of survey thoracic radiographic and/or barium esophagram findings of displacement of the esophagogastric junction and stomach into the thoracic cavity; the diagnosis was confirmed by surgery in 9 dogs and at necropsy in 2 dogs. Megaesophagus (n = 7), gastroesophageal reflux (n = 4), and esophageal hypomotility (n = 1) were additional findings in some dogs. Aspiration pneumonia was diagnosed in 7 of the dogs. Medical therapies formulated for the therapy of presumed reflux esophagitis generally failed to resolve the clinical signs associated with the hiatal hernia. Hiatal herniae were surgically repaired in 9 of the Shar-Peis by various combinations of diaphragmatic crural apposition, fixation of the esophagus to the diaphragmatic crus (esophagopexy), and left fundic tube gastropexy. Eight of the animals survived surgery, six of which have been asymptomatic since surgery (19 to 36 months). The megaesophagus, esophageal hypomotility, and bronchopneumonia resolved in all of these dogs.

Administration, Oral↗