Biology subjects

Parker, L.

Publications and source records attributed to Parker, L..

3 recordsLinked to original sources

bioRxiv2026

Optimizing irrigation during heat events sustains grapevine physiology and fruit production

O_LIIncreasing frequency, intensity, and duration of heat waves (HWs) threaten agricultural production globally by constraining physiological function and fruit production. Supplemental irrigation mitigates heat stress in grapevine and other woody perennial crops, yet water scarcity necessitates optimized irrigation strategies during extreme heat. C_LIO_LIWe conducted a three-year field trial in a commercial Cabernet Sauvignon vineyard, applying differential irrigation only before and during naturally occurring HWs: baseline (50% ET), moderate (90-120% ET), and high (120-180% ET). We monitored water potentials, leaf gas exchange, canopy temperature, yield, and berry composition. C_LIO_LIBaseline irrigation consistently reduced net photosynthesis, stomatal conductance, and leaf cooling capacity during HWs. Moderate supplemental irrigation maintained gas exchange, transpiration, and leaf temperature, mitigating yield losses. Excessive irrigation beyond moderate levels provided no additional physiological benefit and decreased crop water use efficiency and berry quality. C_LIO_LIOur results demonstrate that targeted, event-based irrigation sustains grapevine physiological performance and fruit production under extreme heat, whereas both insufficient and excessive water negatively affect carbon assimilation, stomatal regulation, and crop productivity. These findings emphasize the importance of aligning water management with heat event timing to preserve vine function, optimize water use, and maintain yield and fruit quality in water-limited regions. C_LI

plant biology↗

bioRxiv2021

Pharmacokinetics and Central Accumulation of Delta-9-Tetrahydrocannabinol (THC) and its Bioactive Metabolites are Influenced by Route of Administration and Sex

Up to a third of North Americans over 16 years old report using cannabis in the prior month, most commonly through inhalation. Animal models that reflect human cannabis consumption are critical to study its impacts on brain and behaviour. Nevertheless, most animal studies to date examine effects of cannabis through injection of delta-9-tetrahydrocannabinol (THC; primary psychoactive component of cannabis). THC injections produce markedly different physiological and behavioural effects than inhalation, likely due to distinctive pharmacokinetics of each administration route. The current study directly examined if administration route (injection versus inhalation), with dosing being matched on peak THC blood levels, alters the metabolism of THC, and the central accumulation of THC and its metabolites over time. Adult male and female Sprague-Dawley rats received either a single intraperitoneal injection of THC (2.5 mg/kg) or a single (15 min) session of inhaled exposure to THC distillate (100 mg/mL) vapour. Blood and brains were collected at 15, 30, 60, 90 and 240 minutes post-exposure for analysis of THC and metabolites through mass spectrometry-liquid chromatography. Inhalation results in immediate hypothermia, whereas injection results in delayed hypothermia. Despite achieving comparable peak concentrations of blood THC in both groups, our results indicate higher initial brain THC concentration following inhalation, whereas injection resulted in dramatically higher 11-OH-THC concentrations, a potent THC metabolite, in blood and brain that increased over time. Our results provide evidence that THC and its metabolites exhibit different pharmacokinetic profiles following inhalation versus injection, which could have significant impacts for data interpretation and generalizability. Accordingly, we suggest that translational work in the realm of THC and cannabis strongly consider using inhalation models over those that employ injection. HighlightsO_LIBody temperature as well as blood and brain levels of THC and metabolites differ based on administration route C_LIO_LITHC inhalation results in immediate hypothermia, whereas THC injection results in delayed hypothermia C_LIO_LITHC inhalation results in higher initial brain THC levels than injection C_LIO_LITHC injection results in higher blood & brain 11-OH-THC levels than inhalation C_LIO_LITranslational cannabis work should strongly consider using inhalation over injection C_LI

neuroscience↗

bioRxiv2017

NuMA is a negative regulator of 53BP1 in DNA double-strand break repair

Accumulation of 53BP1 at DNA breaks determines DNA repair pathway choice and promotes checkpoint activation. Here, we show regulation of 53BP1 beyond repair foci. 53BP1 movements are constrained in the nucleoplasm and increase in response to DNA damage. 53BP1 interacts with the structural protein NuMA, which controls 53BP1 diffusion. This interaction, and colocalization between the two proteins in vitro and in breast tissues, is reduced after DNA damage. In cell lines and breast carcinoma, NuMA prevents 53BP1 accumulation at DNA breaks and high NuMA expression predicts better patient outcomes. Manipulating NuMA expression alters PARP inhibitor sensitivity of BRCA1-null cells, end-joining activity, and immunoglobulin class switching that rely on 53BP1. We propose a new mechanism that involves the sequestration of 53BP1 by NuMA in the absence of DNA damage. Such mechanism may have evolved to disable repair functions and may be a decisive factor for tumor responses to genotoxic treatments.

cell biology↗