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M Max

Publications and source records attributed to M Max.

7 recordsLinked to original sources
PubMed1992

Regulation of melatonin production by light, darkness, and temperature in the trout pineal.

The pineal gland of the rainbow trout, Salmo gairdneri, when kept under in vitro perifusion culture conditions, displays a consistently elevated level of melatonin production in darkness (Gern and Greenhouse 1988). Upon light exposure melatonin production falls and stabilizes at a new lower level that is dependent upon the irradiance of the stimulus. To achieve the maximal response for each irradiance, the duration of the stimulus must exceed 30 min. The response amplitude is maximally sensitive to photons presented over durations of 30-45 min; is very insensitive to shorter light exposures; and is maintained with no evidence of adaptation over longer exposures. Temperature plays a role in regulation of melatonin production both in darkness and during light exposure; increased temperature increases melatonin production in darkness and also increases the sensitivity of the response to light. The action spectrum for the response is best fit by the Dartnall nomogram for a vitamin A1 based rhodopsin with peak sensitivity near 500 nm. The possible adaptive significance of control of melatonin synthesis by light and temperature is considered.

Animals↗
PubMed1991

Excitatory amino acid receptors may mediate the effects of light on the reproductive system of the golden hamster.

Seasonal regulation of reproduction occurs in golden hamsters (Mesocricetus auratus) in response to changes in day length (photoperiod). We report here the results of experiments designed to evaluate whether excitatory amino acid neurotransmission is involved in mediating the effects of light on reproduction. We found that MK-801, a specific antagonist of the N-methyl-D-aspartate subclass of excitatory amino acid receptors, blocked the stimulatory action of short pulses of light on gonadal function in hamsters maintained in short days. Furthermore, MK-801 also inhibited the light-induced decline in pineal melatonin content. These findings suggest that excitatory amino acids may mediate the effects of light on the reproductive system.

Amino Acids↗
PubMed1987

Surface area sized of intravitreal iron wires: their effects on the electroretinograms of rats.

UNLABELLED: The electroretinogram (ERG) was recorded 20 times over a period of 360 days in 26 albino-rats with implanted intravitreal iron wires ranging in size between 0.15 and 1.2 mm2. RESULTS: (i) The a- and b-wave amplitudes decreased rapidly within one day after iron wire implantation. During the following week the amplitudes recovered to some extent. In the course of the next few months the a- and b-wave amplitudes of the eyes implanted with the largest iron wires (1.2 mm2) decreased steadily to about 20% by the end of the observation time, whereas in the groups containing smaller iron wires the electroretinographic changes were limited. (ii) Implantation of equally-sized glass splinters reduced the a- and b-wave amplitudes to 65-75% in comparison to the intact fellow eye. Fast recovery of both potentials to 83-93% followed within two weeks. The mean values of the a-wave amplitudes reached nearly 100%, those of the b-wave 90-95% in the next month.

Animals↗
PubMed1985

The organization of retinal projections to the diencephalon and pretectum in the cichlid fish, Haplochromis burtoni.

The organization of retinofugal projections was studied in a cichlid fish by labelling small groups of retinal ganglion cell axons with either horseradish peroxidase or cobaltous lysine. Two major findings resulted from these experiments. First, optic tract axons show a greater degree of pathway diversity than was previously appreciated, and this pathway diversity is related to the target nuclei of groups of axons. The most striking example is the formation of the medial optic tract. Fibers that will become the medial optic tract move abruptly away from their neighbors, at about the level of the optic chiasm, and coalesce at the dorsomedial edge of the marginal optic tract. The medial optic tract projects to the thalamus, the dorsal pretectum, and the deep layer of the optic tectum. The axial optic tract is a group of fibers which segregates from the most medial portion of the marginal optic tract, at about the level of the optic chiasm. The axial tract stays medial to the marginal optic tract for a few hundred microns and then curves laterally to rejoin the marginal optic tract. At least some axial trat axons terminate in the suprachiasmatic nucleus. Within the marginal optic tract, retinal ganglion cell axons from a given retinal quadrant are always segregated into at least two groups. The smaller group projects to the superficial pretectal nucleus. The larger group projects to the superficial layer of the optic tectum. Second, each nontectal retinal termination site receives a unique pattern of retinal input. Within the pretectum the parvocellular superficial pretectal nucleus receives a highly retinotopically organized input from all retinal regions; the basal optic nucleus receives a roughly retinotopically organized input from all retinal regions; the dorsal pretectum receives an input from all retinal regions; and the central pretectal nucleus receives input only from the ventral hemiretina. Within the diencephalon the thalamus receives an input from all retinal regions, but this input is not retinotopically organized; the suprachiasmatic nucleus receives input from the region of central retina that lies just dorsal to the optic nerve head, via the axial optic tract. The accessory optic nucleus receives input from the dorsal hemiretina.

Animals↗
PubMedDate not supplied

Acute hypercalcemic crisis.

Although hypercalcemia may be caused by extraparathyroid disease and controlled with various medications, acute hypercalcemic crisis is a surgical emergency. All nonperative measures are directed toward diagnosis of hyperparathyroidism and preparation for operation. Parathyroidectomy is indicated even in the absence of definite evidence of a functioning parathyroid tumor in patients when nonoperative methods fail. Prompt medical therapy and timely surgical intervention will result in success in the vast majority of patients with hypercalcemic crises.

Acute Disease↗